[edit] Plot
The Others plan to attack the camp and kidnap pregnant women for scientific research. The survivors are informed of the plan by the Other Karl (Blake Bashoff) and conceive a plan to kill the Others with dynamite-rigged tents. Sayid Jarrah (Naveen Andrews), Jin Kwon (Daniel Dae Kim) and Bernard Nadler (Sam Anderson) remain at the beach, tasked with shooting the dynamite-rigged tents while the rest of the survivors journey with Danielle Rousseau (Mira Furlan) to the radio tower to communicate with Naomi Dorrit's (Marsha Thomason) nearby ship. The Others arrive, and while Sayid and Bernard detonate their tents, Jin misses his target, which results in their capture by the Others: Tom (M.C. Gainey), Ryan Pryce (Brian Goodman) and Jason (Ariston Green), and the deaths of seven Others. After hearing only two explosions, James "Sawyer" Ford (Josh Holloway) and Juliet Burke (Elizabeth Mitchell) turn back to see if they can help. Hugo "Hurley" Reyes (Jorge Garcia), who was not allowed to accompany Sawyer and Juliet because of his weight, drives the van he found onto the beach, and the captives gain the upper hand, killing the remaining Others with the help of Sawyer and Juliet. Tom surrenders but Sawyer shoots him in the chest anyway.
After knocking Desmond Hume (Henry Ian Cusick) unconscious, Charlie Pace (Dominic Monaghan) dives down into The Looking Glass, a research station of the Dharma Initiative, with the hope of disabling the system jamming outgoing transmissions. Charlie is captured by the resident Others Greta (Lana Parrilla) and Bonnie (Tracy Middendorf). Ben Linus (Michael Emerson) learns of Charlie's infiltration and sends Mikhail Bakunin (Andrew Divoff) to the station to kill the three to preserve the signal jamming. Mikhail arrives and kills Greta and Bonnie, only to be shot through the chest with a spear gun by Desmond who emerges from a closet inside the station where he had hidden after diving down a short time after Charlie did. Getting the code from Bonnie before she dies (the notes to the middle eight of "Good Vibrations" by the Beach Boys), Charlie disables the signal jammer, and is contacted by Penny Widmore (Sonya Walger) via video transmission. Penny informs Charlie that she does not know Naomi, and did not send the boat that Naomi claims to be from. Despite his injury, Mikhail manages to swim out of the station and blasts the window of the jamming room with a grenade, killing himself and flooding the communications room. Charlie locks the door to save Desmond from drowning with him, but before he drowns, Charlie writes on his hand so Desmond can read: "NOT PENNY'S BOAT".
John Locke (Terry O'Quinn), one of the survivors, has been shot by Ben. Finding his legs paralyzed again, Locke is about to commit suicide, when he is stopped by what appears to be Walt Lloyd (Malcolm David Kelley). Meanwhile, Ben tells Richard Alpert (Nestor Carbonell) to lead the rest of the Others to the "Temple" and then leaves the Others with his adopted daughter, Alex (Tania Raymonde) Rousseau's daughter and Karl's girlfriend, to meet up with the survivors to persuade Jack not to call Naomi's ship for rescue.
Jack informs Kate Austen (Evangeline Lilly) that he loves her, after she witnesses a kiss between him and Juliet. Ben and Alex intercept Jack's group; Ben informs Jack that Naomi is not who she says she is, and making contact with her boat will be disastrous for everyone on the island. Ben orders the shooting of Sayid, Jin, and Bernard, and when Jack hears three shots, he attacks Ben and punches him in the face repeatedly leaving Ben bloody. Unknown to Jack, the shots were fired into the sand, following earlier orders from Ben. Rousseau meets her sixteen year old daughter Alex, who was kidnapped by the Others shortly after her birth, and they tie Ben up. The trek party, now able to get a signal, arrives at the radio tower. Rousseau disables her distress signal, freeing the frequency for Naomi. However, Naomi is knifed in the back by Locke, who threatens to kill Jack if he calls Naomi’s boat. Locke cannot bring himself to kill Jack, who communicates with George Minkowski on Naomi's boat. Minkowski tells the survivors they will be sending rescue.
Throughout the episode, flashforwards from years after "Through the Looking Glass"'s island events show that Jack has escaped the island and returned to work as a spinal surgeon, although it's not till the last one when Kate appears and Jack discusses the island that it becomes clear that they are flashforwards rather than flashbacks. He is depressed, bearded, heavily drinking and addicted to Oxycodone. After reading about the death of someone he knew, Jack goes to commit suicide by jumping off the Sixth Street Viaduct bridge. He is distracted by a car wreck and goes to save those in need. Jack visits the memorial service for the person he read about and finds himself to be the only attendee. Jack contacts Kate and tells her about the memorial service. Kate says that she did not know about it, but she would not have attended even if she did. Jack also confesses to using the "golden pass" that they were given by Oceanic Airlines to fly across the Pacific Ocean and back every Friday, hoping that he will crash on the island. Jack explains that they should never have left the island and must return; however, Kate disagrees and leaves, not wanting to continue this conversation that they have apparently had before.
[edit] Production
The title is an allusion to Lewis Carroll's novel Through the Looking-Glass, and What Alice Found There and a reference to the fictitious Dharma Initiative station found in the previous episode. Shooting began on April 13, 2007 and ended on May 7, 2007. The writers were so far behind schedule that parts of the episode were shot while later parts were still being written. Filming mostly took place on Oahu, Hawaii, with additional scenes shot in Los Angeles. The hospital scenes were filmed on the same sets used for the ABC show Grey's Anatomy.
Despite not being mentioned in the official press release, then 15 year old Malcolm David Kelley returned to reprise his role as 10 year old Walt Lloyd, and received credit as a "special guest star". Kelley’s character had left the island in the second season finale, only 26 days prior to the events of "Through the Looking Glass", however, Kelley had not filmed an episode in over a year. In his single scene, Walt has visibly aged, appears taller and has a deeper voice. The producers had hoped that Harold Perrineau, who plays Walt's father Michael Dawson, would return in this episode, but he was busy filming the pilot for CBS' Demons. Perrineau instead returned to Lost in season 4. . Damon Lindelof and Carlton Cuse lent their voices for the unseen roles of the flight captain and newscaster, respectively.
This episode concluded the story arc about Charlie's death, which began earlier in the season when Desmond prophesied Charlie's death. Throughout the season, Charlie escaped death; however, Desmond told Charlie that he had to die in order for his girlfriend, Claire Littleton, to get rescued from the island. The storyline of Charlie's death was conceived while producing the latter part of the second season, after the storyline of Charlie's drug addiction finished. The news of his character's death was broken to Monaghan two episodes in advance, to which Monaghan felt "relief" for knowing the future of his job on the show. On the night of Monaghan's second to last day on set, he was presented with a canoe paddle that had been made by the cast and crew. Monaghan hoped to return to Lost as a guest star in flashbacks or dreams.
Jack Bender stated that Matthew Fox "really commits body and soul into the story he's telling" and Fox questioned whether he had ever been more tired than while shooting the double episode. Like the other Lost season finales, the final cliffhanger scene was given a codename—"The Rattlesnake in the Mailbox"—and kept top secret. After Lindelof and Cuse wrote the scene, only Fox, Lilly, Bender and co-executive producer Jean Higgins were given copies of the script. The scene was shot with a green screen in an abandoned Honolulu parking lot with the airport edited in. Despite the security measures, a complete and detailed episode synopsis was uploaded online over a week before the episode aired. Disney investigated the leak. The leak prompted Lindelof and Cuse to enter "radio silence", which was temporarily broken at Comic-Con International 2007. The funeral parlor that Jack visits is called "Hoffs/Drawlar", which is an anagram of "flashforward". The idea of flashforwards was conceived by creators Lindelof and Abrams during the show's conception. However, Cuse and Lindelof only started fleshing out the idea at the end of the first season, after they realized that flashbacks would eventually stop being revelatory and knew that they would eventually have to switch to flashforwards. With the announcement that the series would conclude 48 episodes after "Through the Looking Glass", they felt comfortable playing flashforwards as early as the third season finale.
Post-production wrapped on May 21, 2007, only two days before it aired on television. The score was composed by series musician Michael Giacchino, while popular music was also featured throughout the episode. Charlie also sings a song in the episode that was written by Dominic Monaghan, who plays him. A Lost season finale is approximately twice as long the average Lost episode. Due to the episode's length, it was split into two parts in some countries and when released on DVD. Unlike most episodes, this episode did not feature a "previously on Lost…" recap at the start of the episode when it first aired; however, it was originally preceded by a clip-show titled "Lost: The Answers", which recapped the third season. Cuse said that he and Lindelof think the finale is "very cool [and] we're very proud of it." Stephen McPherson, the president of ABC Entertainment, called "Through the Looking Glass" "one of the best episodes" of the series. Buena Vista Home Entertainment released "Through the Looking Glass" on the season's DVD and Blu-ray Disc sets on December 11, 2007 in Region 1. A featurette called "Lost: On Location" features cast and crew discussing production of select episodes, including "Through the Looking Glass". The episode was rerun for the first time on January 30, 2008 with on-screen text in the lower third of the screen, similar to VH1's Pop-up Video. These pop-ups were not written by Lost's writers due to the 2007–2008 Writers Guild of America strike; they were written by the marketing company Met/Hodder. This enhanced edition was viewed by almost 9 million Americans.
[edit] Reception
[edit] Ratings
In the U.S., the episode brought in the best ratings for Lost in fifteen episodes. The two-hour Wednesday broadcast on ABC made Lost the fourth most watched series of the week with an average of 13.86 million American viewers, below the third season average of 14.6 million. The first hour was viewed by 12.67 million, and the audience increased to 15.04 million in the second hour. The episode received a 5.9/15 in the key adults 18–49 demographic. In the United Kingdom, the episode attracted 1.21 million viewers, and was the second most watched program of the week on the non-terrestrial channels, beaten only by Katie & Peter: The Next Chapter. In Australia, Lost was the thirty-seventh most viewed show of the week, bringing in 1.17 million viewers. In Canada, the episode placed sixteenth for the first half, with 911,000 viewers and fifteenth for the second half, with 938,000 viewers. The episodes were broadcast before and after American Idol.
[edit] Critical response
The episode garnered critical acclaim. The Los Angeles Times wrote that the episode was "an unusually action-packed and sanguinary spring cleaning that… left a host of… characters… dead", Access Atlanta said "it was deeply satisfying. The first hour started a bit slow but the second hour had great twists, wonderfully emotional moments, both happy and sad", and the Associated Press said that "the powerful season-ending episode redeemed the series with the shrewdness and intrigue that made it so addictive in the first place." The San Francisco Chronicle wrote that "not only was the pace fast, the teases taut, and the answers plenty, the writers took a compelling gamble… [by telling] viewers that in the future… maybe all… of the people on the Lost island get off. They get their wish. But in Jack, our guide through this series, the writers definitively say, 'Be careful what you wish for.'" The San Jose Mercury News called the finale a "jaw-dropping exercise in good storytelling." The Pittsburgh Post-Gazette commented that the flashforward "twist gave the saga renewed momentum as it begins its march toward a 2010 finish." The season finale was summed up as "a mind-blower, for sure, a radical two hours that gave us major fake-outs, an army of dead bodies, the possibility of rescue [and] diverse portraits of heroism" by The Boston Globe, who added that the death of Charlie was "the most touching loss of the series so far." The Palm Beach Post and Wizard named it the "Best Cliffhanger" of 2007. The Chicago Tribune called it "a qualified success" with excellent pacing and action, however, the flashforward scenes were thought to be uninteresting and "clumsy". Time ranked the episode as the best of 2007 and the "Rattlesnake in the Mailbox" as one of the ten best scenes of 2007 television.
The Futon Critic placed the episode first in the site's annual "50 Best Episodes" list. E! said that "Through the Looking Glass" was possibly "the best episode ever of the entire series." TV Guide described "Through the Looking Glass" as "a dizzying exercise in adventure, sustained tension and time-shifting rug pulling [that was] spectacularly produced, amazingly directed and gloriously acted." IGN gave the double episode a perfect 10/10 – the best review of the season – saying it was "nothing short of a masterpiece of storytelling with a brilliantly paced narrative." IGN would conclude that the flashforward was the "Biggest Shock" in 2007 television. BuddyTV praised the unpredictability, saying that "no other show can even attempt to do what Lost does." BuddyTV would later call "Through the Looking Glass" the best finale of 2007 and Charlie's death the saddest TV death of 2007. "Through the Looking Glass" was TV.com's "Editor's Choice" for "Best Episode" of 2007. AOL's TV Squad gave the episode a 7/7, noting that "the writers followed through on Desmond's premonitions and successfully delivered the highly anticipated game-changer." Television Without Pity gave the third season finale an "A". The Sydney Morning Herald wrote that Lost "may have unjumped [the shark] with [the] flashforward." Entertainment Weekly ranked it as one of the top ten episodes of 2007, saying that the cliffhanger "[revealed] new dimensions to [Lost's] creative world." Zap2It questioned "whether to be deeply frustrated (again), really, really confused (a distinct possibility) or just in awe of the incredible mind-(ahem) show runners… have pulled off." The writing for Locke was criticized, and one IGN writer said that "it seems irrational that he would go and [stab Naomi] in the back without explaining himself." Lindelof stated "that we might be willing to give [Locke] the benefit of the doubt for any action he took in response to [lying, gutshot, in a pit of Dharma corpses for two days and on the verge of taking his own life], even if considered slightly 'out of character'." Film and television director and writer Kevin Smith said that "to do seasons and then suddenly throw a massive curveball is just so dramatically satisfying, you just take your hats off to the writers in a big, bad way."
[edit] Awards
The episode was nominated in the categories of "Outstanding Directing for a Drama Series", "Outstanding Writing for a Drama Series" and "Outstanding Single-Camera Picture Editing for a Drama Series" for the 59th Primetime Emmy Awards, but it failed to win in any category. The season finale was submitted for Emmy consideration in the category of "Outstanding Drama Series"; however, it was not nominated. Bender was also nominated for the Directors Guild of America Award for "Outstanding Directorial Achievement in Dramatic Series Night", but he did not win. "Through the Looking Glass" was the AOL primetime poll winner and editors' pick for "Best Season-Ending Cliffhanger". "Through the Looking Glass" won "Drama Episode of the Year" at the Los Angeles Times Gold Derby TV Awards. The episode was awarded three E! Tater Top Awards. Charlie's death won "Biggest Tearjerker" and the "Rattlesnake" won "Biggest Shocker", while Rose Henderson won "Best Line" for "If you say 'live together, die alone' to me, Jack, I'm going to punch you in your face."

Summary:
"Through the Looking Glass" is the third season finale of the ABC television series Lost, consisting of the twenty-second and twenty-third episodes of the third season. It is also the seventy-first and seventy-second episodes overall. It was written by co-creator/executive producer Damon Lindelof and executive producer Carlton Cuse, and directed by executive producer Jack Bender. When first aired on May 23, 2007 in the United States and Canada, it was watched by an average of fourteen million American viewers. Like the previous two season finales, it was two hours long with advertisements, twice the length of a normal episode. It was edited into two individual episodes when released on DVD. The season finale is widely regarded as one of the best episodes of Lost. The episode garnered a number of awards and nominations, including three Emmy nominations and a DGA Award nomination.
The episode begins its narrative in late December 2004, over ninety days after the crash of Oceanic Airlines Flight 815. The battle between the crash survivors and the dangerous and mysterious island inhabitants referred to as the "Others" comes to a head as ten of the Others attack and are then ambushed at the survivors' camp and are subsequently killed. Meanwhile, Jack Shephard (played by Matthew Fox) leads most of the survivors to the island's radio tower to communicate with a nearby ship. Intercut with this story are off-island scenes spotlighting Jack, who has become suicidally depressed and addicted to painkillers. In a twist ending, it is revealed that these scenes are flashforwards to sometime in the future, after Jack has left the island, rather than flashbacks as in previous episodes of Lost.


Amateur career
Early years
Earvin Johnson Jr. was born to Earvin Sr., a General Motors assembly worker, and Christine, a school custodian. Johnson grew up in Lansing, Michigan, and came to love basketball as a youngster, idolizing players such as Earl Monroe and Marques Haynes, and practicing "all day".
Johnson was first dubbed "Magic" as a 15-year-old sophomore playing for Lansing's Everett High School, when he recorded a triple-double of 36�points, 18�rebounds and 16�assists. After the game, Fred Stabley Jr., a sports writer for the Lansing State Journal, gave him the moniker despite the belief of Johnson's mother, a Christian, that the name was sacrilegious. In his final high school season, Johnson led Lansing Everett to a 27–1 win–loss record while averaging 28.8�points and�16.8 rebounds per game, and took his team to an overtime victory in the state championship game.
Michigan State University
Although Johnson was recruited by several top-ranked colleges such as Indiana and UCLA, he decided to play close to home. He initially wanted to attend the University of Michigan, but decided on Michigan State University in East Lansing, after the school's basketball coach, Jud Heathcote, promised that Johnson could play the point guard position.
Johnson did not initially aspire to play professionally, focusing instead on his communication studies major and on his desire to become a television commentator. Playing with future NBA draftees Greg Kelser, Jay Vincent and Mike Brkovich, Johnson averaged 17.0�points, 7.9�rebounds, and 7.4�assists per game as a freshman, and led the Spartans to a 25–5�record, the Big Ten Conference title, and a berth in the 1978 NCAA Tournament. The Spartans reached the Elite Eight, but lost narrowly to eventual national champion Kentucky.
During the 1978–79 season, Michigan State again qualified for the NCAA Tournament, where they advanced to the championship game and faced Indiana State University, which was led by senior Larry Bird. In what was the most-watched college basketball game ever, Michigan State defeated Indiana State 75–64, and Johnson was voted Most Outstanding Player of the Final Four. After two years in college, during which he averaged 17.1�points, 7.6�rebounds, and 7.9�assists per game, Johnson declared himself eligible for the 1979 NBA Draft.
Professional career
Rookie season in the NBA (1979–80)
Johnson was drafted first overall in 1979 by the Los Angeles Lakers. Johnson said that what was "most amazing" about joining the Lakers was the chance to play alongside Kareem Abdul-Jabbar, the team's 7�ft 2�in (2.18�m) center who became the leading scorer in NBA history. Despite Abdul-Jabbar's dominance, he had failed to win a championship with the Lakers, and Johnson was expected to help them achieve that goal. Johnson averaged 18.0�points, 7.7�rebounds, and 7.3�assists per game for the season, was selected to the NBA All-Rookie Team, and was named an NBA All-Star Game starter.
The Lakers compiled a 60–22�record in the regular season and reached the 1980 NBA Finals, in which they faced the Philadelphia 76ers, who were led by forward Julius Erving. The Lakers took a 3–2�lead in the series, but Abdul-Jabbar, who averaged 33�points a game in the series, sprained his ankle in Game 5 and could not play in Game 6. Paul Westhead decided to start Johnson at center in Game 6; Johnson recorded 42�points, 15�rebounds, seven�assists, and three steals in a 123–107 win, while playing guard, forward, and center at different times during the game. Johnson became the only rookie to win the NBA Finals MVP award, and his clutch performance is still regarded as one of the finest in NBA history. He also became one of four players to win NCAA and NBA championships in consecutive years.
Ups and downs (1980–83)
Early in the 1980–81 season, Johnson was sidelined after he suffered torn cartilage in his left knee. He missed 45�games, and said that his rehabilitation was the "most down" he had ever felt. Johnson returned before the start of the 1981 playoffs, but the Lakers' then-assistant and future head coach Pat Riley later said Johnson's much-anticipated return made the Lakers a "divided team". The 54-win Lakers faced the 40–42 Houston Rockets in the first round of playoffs, where Houston upset the Lakers 2–1 after Johnson airballed a last-second shot in Game 3.
During the off-season, Johnson signed a 25-year, $25�million contract with the Lakers, which was the highest-paying contract in sports history up to that point. At the beginning of the 1981–82 season, Johnson had a heated dispute with Westhead, who Johnson said made the Lakers "slow" and "predictable". After Johnson demanded to be traded, Lakers owner Jerry Buss fired Westhead and replaced him with Riley. Although Johnson denied responsibility for Westhead's firing, he was booed across the league, even by Lakers' fans. Despite his off-court troubles, Johnson averaged 18.6�points, 9.6�rebounds, 9.5�assists, and a league-high 2.7�steals per game, and was voted a member of the All-NBA Second Team. He also joined Wilt Chamberlain and Oscar Robertson as the only NBA players to tally at least 700�points, 700�rebounds, and 700�assists in the same season. The Lakers advanced through the 1982 playoffs and faced Philadelphia for the second time in three years in the 1982 NBA Finals. After a triple-double from Johnson in Game 6, the Lakers defeated the Sixers 4–2, as Johnson won his second NBA Finals MVP award. During the championship series against the Sixers, Johnson averaged 16.2�points on .533�shooting, 10.8�rebounds, 8.0�assists, and 2.5�steals per game. Johnson later said that his third season was when the Lakers first became a great team, and he credited their success to Riley.
During the 1982–83 NBA season, Johnson averaged 16.8�points, 10.5�assists, and 8.6�rebounds per game and earned his first All-NBA First Team nomination. The Lakers again reached the Finals, and for a third time faced the Sixers, who featured center Moses Malone as well as Erving. With Johnson's teammates Norm Nixon, James Worthy and Bob McAdoo all hobbled by injuries, the Lakers were swept by the Sixers, and Malone was crowned the Finals MVP. In a losing effort against Philadelphia, Johnson averaged 19.0�points on .403�shooting, 12.5�assists, and 7.8�rebounds per game.
Battles against the Celtics (1983–87)
In Johnson's fifth season, he averaged a double-double of 17.6�points and 13.1�assists, as well as 7.3�rebounds per game. The Lakers reached the Finals for the third year in a row, where Johnson's Lakers and Bird's Celtics met for the first time in the post-season. The Lakers won the first game, and led by two points in Game 2 with 18�seconds to go, but after a layup by Gerald Henderson, Johnson failed to get a shot off before the final buzzer sounded, and the Lakers lost 124–121 in overtime. In Game 3, Johnson responded with 21�assists in a 137–104 win, but in Game 4, he again made several crucial errors late in the contest. In the final minute of the game, Johnson had the ball stolen by Celtics center Robert Parish, and then missed two free throws that could have won the game. The Celtics won Game 4 in overtime, and the teams split the next two games. In the decisive Game 7 in Boston, as the Lakers trailed by three points in the final minute, opposing point guard Dennis Johnson stole the ball from Johnson, a play that effectively ended the series. During the Finals, Johnson averaged 18.0�points on .560�shooting, 13.6�assists, and 7.7�rebounds per game. Johnson later described the series as "the one championship we should have had but didn't get".
In the regular season, Johnson averaged 18.3�points, 12.6�assists, and 6.2�rebounds per game and led the Lakers into the 1985 NBA Finals, where they faced the Celtics again. The series started poorly for the Lakers when they allowed an NBA Finals record 148�points to the Celtics in a 34-point loss in Game 1. However, Abdul-Jabbar, who was now 38�years old, scored 30�points and grabbed 17�rebounds in Game 2, and his 36�points in a Game 5 win were instrumental in establishing a 3–2 lead for Los Angeles. After the Lakers defeated the Celtics in six games, Abdul-Jabbar and Johnson, who averaged 18.3�points on .494�shooting, 14.0�assists, and 6.8�rebounds per game in the championship series, said the Finals win was the highlight of their careers.
Johnson again averaged a double-double in the 1985–86 NBA season, with 18.8�points, 12.6�assists, and 5.9�rebounds per game. The Lakers advanced to the Western Conference Finals, but were unable to defeat Houston, who advanced to the Finals in five games. In the next season, Johnson averaged a career-high of 23.9�points, as well as 12.2�assists and 6.3�rebounds per game, and earned his first regular season MVP award. The Lakers met the Celtics for the third time in the NBA Finals, and in Game 4 Johnson hit a last-second hook shot over Celtics big men Parish and Kevin McHale to win the game 107–106. The game-winning shot, which Johnson dubbed his "junior, junior, junior sky-hook", helped Los Angeles defeat Boston in six games. Johnson was awarded his third Finals MVP title after averaging 26.2�points on .541�shooting, 13.0�assists, 8.0�rebounds, and 2.33�steals per game.
Repeat and falling short (1987–91)
Before the 1987–88 NBA season, Lakers coach Pat Riley publicly promised that they would defend the NBA title, even though a team had not won consecutive titles since the 1969 NBA Finals. Johnson had another productive season with averages of 19.6�points, 11.9�assists, and 6.2�rebounds per game. In the 1988 playoffs, the Lakers survived two 4–3�series against the Utah Jazz and the Dallas Mavericks to reach the Finals and face the Detroit Pistons, known as the "Bad Boys" for their physical style of play. After the teams split the first six games, Lakers forward and Finals MVP James Worthy had his first career triple-double of 36�points, 16�rebounds, and 10�assists, and led his team to a 108–105�win. Despite not being named MVP, Johnson had a strong championship series, averaging 21.1�points on .550�shooting, 13.0�assists, and 5.7�rebounds per game.
In the 1988–89 NBA season, Johnson's 22.5�points, 12.8�assists, and 7.9�rebounds per game earned him his second MVP award, and the Lakers reached the 1989 NBA Finals, in which they again faced the Pistons. However, after Johnson went down with a hamstring injury in Game 2, the Lakers were no match for the Pistons, who swept them 4–0.
Playing without the retired Abdul-Jabbar for the first time, Johnson won his third MVP award after a strong 1989–90 NBA season in which he averaged 22.3�points, 11.5�assists, and 6.6�rebounds per game. However, the Lakers bowed out to the Phoenix Suns in the Western Conference semifinals, which was the Lakers' earliest playoffs elimination in nine years. Johnson performed well during the 1990–91 NBA season, with averages of 19.4�points, 12.5�assists, and 7.0�rebounds per game, and the Lakers reached the 1991 NBA Finals. There they faced the Chicago Bulls, led by shooting guard Michael Jordan, a five-time scoring champion regarded as the finest player of his era. Although the series was portrayed as a matchup between Johnson and Jordan, Bulls forward Scottie Pippen primarily defended against Johnson, doing an effective job. Despite two triple-doubles from Johnson during the series, Finals MVP Jordan led his team to a 4–1�win. In the last championship series of his career, Johnson averaged 18.6�points on .431�shooting, 12.4�assists, and 8.0�rebounds per game.
HIV announcement and Olympics (1991–92)
After a physical before the 1991–92 NBA season, Johnson discovered that he had tested positive for HIV. In a press conference held on November�7, 1991, Johnson made a public announcement that he would retire immediately. He stated that his wife Cookie and their unborn child did not have HIV, and that he would dedicate his life to "battle this deadly disease". Johnson initially said that he did not know how he contracted the disease, but later admitted that it was through having multiple sexual partners during his playing career. At the time, only a small percentage of HIV-positive people had contracted it from heterosexual sex, and it was initially rumored that Johnson was gay or bisexual, although he denied both. Johnson's announcement became a major news story in the United States, and in 2004 was named as ESPN's seventh most memorable moment of the past 25 years. Many articles praised Johnson as a hero, and former U.S. President George H. W. Bush said, "For me, Magic is a hero, a hero for anyone who loves sports."
Despite his retirement, Johnson was voted by fans as a starter for the 1992 NBA All-Star Game, although his former teammates Byron Scott and A. C. Green said that Johnson should not play, and several NBA players, including Utah Jazz forward Karl Malone, argued that they would be at risk of contamination if Johnson suffered an open wound while on court. Johnson led the West to a 153–113�win and was crowned All-Star MVP after recording 25�points, 9�assists, and 5�rebounds. The game ended after he made a last-minute three-pointer, and players from both teams ran onto the court to congratulate Johnson.
Johnson was chosen to compete in the 1992 Summer Olympics for the US basketball team, dubbed the "Dream Team" because of the NBA stars on the roster. During the tournament, which the USA won easily, Johnson played infrequently because of knee problems, but he received standing ovations from the crowd, and used the opportunity to inspire HIV-positive people.
Post-Olympics and later life
Before the 1992–93 NBA season, Johnson announced his intention to stage an NBA comeback. After practicing and playing in several pre-season games, he returned to retirement before the start of the regular season, citing controversy over his return sparked by opposition from several active players. During his retirement, Johnson has written a book on safer sex, run several businesses, worked for NBC as a commentator, and toured Asia and Australia with a basketball team that comprised former college and NBA players.
He returned to the NBA as coach of the Lakers near the end of the 1993–94 NBA season, replacing Randy Pfund. After losing five of six games, Johnson announced he would resign after the season, choosing instead to purchase a 5% share of the team in June 1994. In the following season, at the age of 36, Johnson attempted another comeback as a player. Playing power forward, he averaged 14.6�points, 6.9�assists, and 5.7�rebounds per game in the last 32�games of the season. After the Lakers lost to the Houston Rockets in the first round of the playoffs, Johnson retired permanently, saying, "I am going out on my terms, something I couldn't say when I aborted a comeback in 1992."
Off the court
Personal life
Johnson first fathered a son in 1981, when Andre Johnson was born to Melissa Mitchell. Although Andre was raised by his mother, he visited Johnson each summer, and as of October 2005 was working for Magic Johnson Enterprises as a marketing director. In 1991, Johnson married Earlitha "Cookie" Kelly, with whom he had one son, Earvin III; the couple adopted a daughter, Elisa, in 1995.
Media figure and business interests
In 1998, Johnson hosted a late night talk show on the Fox network called The Magic Hour, but the show was canceled after two months because of low ratings. He runs Magic Johnson Enterprises, a company that has a net worth of $700�million; its subsidiaries include Magic Johnson Productions, a promotional company; Magic Johnson Theaters, a nationwide chain of movie theaters; and Magic Johnson Entertainment, a movie studio. Johnson has also worked as a motivational speaker. He is a supporter of the Democratic Party—in 2005, he publicly endorsed Phil Angelides for governor of California, and Hillary Clinton for president of the United States. Johnson was an NBA commentator for Turner Network Television for seven years, before becoming a studio analyst for ESPN's NBA Countdown in 2008. Since 1994, Johnson has been a minority owner of the Lakers, having reportedly paid more than $10�million for part ownership. He also holds the title of team vice president. In 2006 Johnson created a contract food service with Sodexo USA called Sodexo-Magic.
HIV activism
After announcing his infection in November 1991, Johnson created the Magic Johnson Foundation to help combat HIV, although he later diversified the foundation to include other charitable goals. In 1992, he joined the National Commission on AIDS, but left after eight months, saying that the commission was not doing enough to combat the disease. He was also the main speaker for the United Nations (UN) World AIDS Day Conference in 1999, and has served as a United Nations Messenger of Peace.
HIV had been associated with drug addicts and homosexuals, but Johnson's campaigns sought to show that the risk of infection was not limited to those groups. Johnson stated that his aim was to "help educate all people about what [HIV] is about" and teach others not to "discriminate against people who have HIV and AIDS". Johnson was later criticized by the AIDS community for his decreased involvement in publicizing the spread of the disease.
To prevent his HIV infection from becoming AIDS, Johnson takes a daily combination of drugs. He has advertised GlaxoSmithKline's drugs, and partnered with Abbott Laboratories to publicize the fight against AIDS in African American communities.
Career achievements
In 905�NBA games, Johnson scored 17,707�points, 6,559�rebounds, and 10,141�assists, translating to career averages of 19.5�points, 7.2�rebounds, and 11.2�assists per game. Johnson shares the single-game playoff record for assists (24), holds the Finals record for assists in a game (21), and has the most playoff assists (2,346). He holds the All-Star Game single-game record for assists (22), and the All-Star Game record for career assists (127). Johnson introduced a fast-paced style of basketball called "Showtime", described as a mix of "no-look passes off the fastbreak, pin-point alley-oops from halfcourt, spinning feeds and overhand bullets under the basket through triple teams." Fellow Lakers guard Michael Cooper said, "There have been times when [Johnson] has thrown passes and I wasn't sure where he was going. Then one of our guys catches the ball and scores, and I run back up the floor convinced that he must've thrown it through somebody." Johnson was exceptional because he played point guard despite being 6�ft 9�in (2.06�m), a size reserved normally for frontcourt players. He combined the size of a power forward, the one-on-one skills of a swingman, and the ball handling talent of a guard, making him one of the most dangerous triple-double threats of all time; his 138�triple-double games are second only to Oscar Robertson's 181.
For his feats, Johnson was voted as one of the 50 Greatest Players of All Time by the NBA in 1996, and was inducted into the Basketball Hall of Fame in 2002. ESPN's SportsCentury ranked Johnson #17 in their "50 Greatest Athletes of the 20th Century" In 2006, ESPN.com rated Johnson the greatest point guard of all time, stating, "It could be argued that he's the one player in NBA history who was better than Michael Jordan." Several of his achievements in individual games have also been named among the top moments in the NBA.
Rivalry with Larry Bird
Johnson and Bird were first linked as rivals after Johnson's Michigan State squad defeated Bird's Indiana State team in the 1979 NCAA finals. The rivalry continued in the NBA, and reached its climax when Boston and Los Angeles met in three out of four NBA Finals from 1984 to 1987. Johnson asserted that for him, the 82-game regular season was composed of 80 normal games, and two Lakers–Celtics games. Similarly, Bird admitted that Johnson's daily box score was the first thing he checked in the morning.
Several journalists hypothesized that the Johnson–Bird rivalry was so appealing because it represented many other contrasts, such as the clash between the Lakers and Celtics, between Hollywood flashiness ("Showtime") and Boston/Indiana blue collar grit ("Celtic Pride"), and between blacks and whites. The rivalry was also significant because it drew national attention to the faltering NBA. Prior to Johnson and Bird's arrival, the NBA had gone through a decade of declining interest and low TV ratings. With the two future Hall of Famers, the league won a whole generation of new fans, drawing both traditionalist adherents of Bird's dirt court Indiana game and those appreciative of Johnson's public park flair. Sports journalist Larry Schwartz of ESPN asserted that Johnson and Bird saved the NBA from bankruptcy.
Despite their on-court rivalry, Johnson and Bird became good friends; ironically, they became close during the filming of a 1984 Converse shoe advertisement that depicted them as enemies. Johnson appeared at Bird's retirement ceremony in 1992, and described Bird as a "friend forever"; during Johnson's Hall of Fame ceremony, Bird formally inducted his old rival.
Works
Biographies
Johnson's autobiography is Johnson, Earvin (1992). Magic Johnson: My Life. Random House. ISBN�0449222543.� Other biographies include:

Summary:
Earvin "Magic" Johnson Jr. (born August 14, 1959) is a retired American professional basketball player who played point guard for the Los Angeles Lakers of the National Basketball Association (NBA). After winning championships in high school and college, Johnson was selected first overall in the 1979 NBA Draft by the Lakers. He won a championship and an NBA Finals Most Valuable Player Award in his rookie season, and won four more championships with the Lakers during the 1980s. Johnson retired abruptly in 1991 after announcing that he had HIV, but returned to play in the 1992 All-Star Game, winning the All-Star MVP Award. After protests from his fellow players, he retired again for four years, but returned in 1996 to play 32�games for the Lakers before retiring for the third and final time.
Johnson's career achievements include three NBA MVP Awards, nine NBA Finals appearances, twelve All-Star games, and ten All-NBA First and Second Team nominations. He led the league in regular-season assists four times, and is the NBA's all-time leader in assists per game, with an average of 11.2. Johnson was a member of the "Dream Team", the U.S. basketball team that won the Olympic gold medal in 1992.
Johnson was honored as one of the 50 Greatest Players in NBA History in 1996, and enshrined in the Basketball Hall of Fame in 2002. He was rated the greatest NBA point guard of all time by ESPN in 2007. His friendship and rivalry with Boston Celtics star Larry Bird, whom he faced in the 1979 NCAA finals and three NBA championship series, were well documented. Since his retirement, Johnson has been an advocate for HIV/AIDS prevention and safe sex, as well as a philanthropist and motivational speaker.


[edit] History
The nucleus was the first organelle to be discovered. The probably oldest preserved drawing dates back to the early microscopist Antonie van Leeuwenhoek (1632 – 1723). He observed a "Lumen", the nucleus, in the red blood cells of salmon . Unlike mammalian red blood cells, those of other vertebrates still possess nuclei. The nucleus was also described by Franz Bauer in 1804 and in more detail in 1831 by Scottish botanist Robert Brown in a talk at the Linnean Society of London. Brown was studying orchids microscopically when he observed an opaque area, which he called the areola or nucleus, in the cells of the flower's outer layer. He did not suggest a potential function. In 1838 Matthias Schleiden proposed that the nucleus plays a role in generating cells, thus he introduced the name "Cytoblast" (cell builder). He believed that he had observed new cells assembling around "cytoblasts". Franz Meyen was a strong opponent of this view having already described cells multiplying by division and believing that many cells would have no nuclei. The idea that cells can be generated de novo, by the "cytoblast" or otherwise, contradicted work by Robert Remak (1852) and Rudolf Virchow (1855) who decisively propagated the new paradigm that cells are generated solely by cells ("Omnis cellula e cellula"). The function of the nucleus remained unclear.
Between 1876 and 1878 Oscar Hertwig published several studies on the fertilization of sea urchin eggs, showing that the nucleus of the sperm enters the oocyte and fuses with its nucleus. This was the first time it was suggested that an individual develops from a (single) nucleated cell. This was in contradiction to Ernst Haeckel's theory that the complete phylogeny of a species would be repeated during embryonic development, including generation of the first nucleated cell from a "Monerula", a structureless mass of primordial mucus ("Urschleim"). Therefore, the necessity of the sperm nucleus for fertilization was discussed for quite some time. However, Hertwig confirmed his observation in other animal groups, e.g. amphibians and molluscs. Eduard Strasburger produced the same results for plants (1884). This paved the way to assign the nucleus an important role in heredity. In 1873 August Weismann postulated the equivalence of the maternal and paternal germ cells for heredity. The function of the nucleus as carrier of genetic information became clear only later, after mitosis was discovered and the Mendelian rules were rediscovered at the beginning of the 20th century; the chromosome theory of heredity was developed.
[edit] Structures
The nucleus is the largest cellular organelle in animals. In mammalian cells, the average diameter of the nucleus is approximately 6 micrometers (μm), which occupies about 10% of the total cell volume. The viscous liquid within it is called nucleoplasm, and is similar in composition to the cytosol found outside the nucleus. It appears as a dense, roughly spherical organelle.
[edit] Nuclear envelope and pores
The nuclear envelope otherwise known as nuclear membrane consists of two cellular membranes, an inner and an outer membrane, arranged parallel to one another and separated by 10 to 50 nanometers (nm). The nuclear envelope completely encloses the nucleus and separates the cell's genetic material from the surrounding cytoplasm, serving as a barrier to prevent macromolecules from diffusing freely between the nucleoplasm and the cytoplasm. The outer nuclear membrane is continuous with the membrane of the rough endoplasmic reticulum (RER), and is similarly studded with ribosomes. The space between the membranes is called the perinuclear space and is continuous with the RER lumen.
Nuclear pores, which provide aqueous channels through the envelope, are composed of multiple proteins, collectively referred to as nucleoporins. The pores are about 125 million daltons in molecular weight and consist of around 50 (in yeast) to 100 proteins (in vertebrates). The pores are 100 nm in total diameter; however, the gap through which molecules freely diffuse is only about 9 nm wide, due to the presence of regulatory systems within the center of the pore. This size allows the free passage of small water-soluble molecules while preventing larger molecules, such as nucleic acids and larger proteins, from inappropriately entering or exiting the nucleus. These large molecules must be actively transported into the nucleus instead. The nucleus of a typical mammalian cell will have about 3000 to 4000 pores throughout its envelope, each of which contains a donut-shaped, eightfold-symmetric ring-shaped structure at a position where the inner and outer membranes fuse. Attached to the ring is a structure called the nuclear basket that extends into the nucleoplasm, and a series of filamentous extensions that reach into the cytoplasm. Both structures serve to mediate binding to nuclear transport proteins.
Most proteins, ribosomal subunits, and some RNAs are transported through the pore complexes in a process mediated by a family of transport factors known as karyopherins. Those karyopherins that mediate movement into the nucleus are also called importins, while those that mediate movement out of the nucleus are called exportins. Most karyopherins interact directly with their cargo, although some use adaptor proteins. Steroid hormones such as cortisol and aldosterone, as well as other small lipid-soluble molecules involved in intercellular signaling can diffuse through the cell membrane and into the cytoplasm, where they bind nuclear receptor proteins that are trafficked into the nucleus. There they serve as transcription factors when bound to their ligand; in the absence of ligand many such receptors function as histone deacetylases that repress gene expression.
[edit] Nuclear lamina
In animal cells, two networks of intermediate filaments provide the nucleus with mechanical support: the nuclear lamina forms an organized meshwork on the internal face of the envelope, while less organized support is provided on the cytosolic face of the envelope. Both systems provide structural support for the nuclear envelope and anchoring sites for chromosomes and nuclear pores.
The nuclear lamina is mostly composed of lamin proteins. Like all proteins, lamins are synthesized in the cytoplasm and later transported into the nucleus interior, where they are assembled before being incorporated into the existing network of nuclear lamina. Lamins are also found inside the nucleoplasm where they form another regular structure, known as the nucleoplasmic veil, that is visible using fluorescence microscopy. The actual function of the veil is not clear, although it is excluded from the nucleolus and is present during interphase. The lamin structures that make up the veil bind chromatin and disrupting their structure inhibits transcription of protein-coding genes.
Like the components of other intermediate filaments, the lamin monomer contains an alpha-helical domain used by two monomers to coil around each other, forming a dimer structure called a coiled coil. Two of these dimer structures then join side by side, in an antiparallel arrangement, to form a tetramer called a protofilament. Eight of these protofilaments form a lateral arrangement that is twisted to form a ropelike filament. These filaments can be assembled or disassembled in a dynamic manner, meaning that changes in the length of the filament depend on the competing rates of filament addition and removal.
Mutations in lamin genes leading to defects in filament assembly are known as laminopathies. The most notable laminopathy is the family of diseases known as progeria, which causes the appearance of premature aging in its sufferers. The exact mechanism by which the associated biochemical changes give rise to the aged phenotype is not well understood.
[edit] Chromosomes
The cell nucleus contains the majority of the cell's genetic material, in the form of multiple linear DNA molecules organized into structures called chromosomes. During most of the cell cycle these are organized in a DNA-protein complex known as chromatin, and during cell division the chromatin can be seen to form the well defined chromosomes familiar from a karyotype. A small fraction of the cell's genes are located instead in the mitochondria.
There are two types of chromatin. Euchromatin is the less compact DNA form, and contains genes that are frequently expressed by the cell. The other type, heterochromatin, is the more compact form, and contains DNA that are infrequently transcribed. This structure is further categorized into facultative heterochromatin, consisting of genes that are organized as heterochromatin only in certain cell types or at certain stages of development, and constitutive heterochromatin that consists of chromosome structural components such as telomeres and centromeres. During interphase the chromatin organizes itself into discrete individual patches, called chromosome territories. Active genes, which are generally found in the euchromatic region of the chromosome, tend to be located towards the chromosome's territory boundary.
Antibodies to certain types of chromatin organization, particularly nucleosomes, have been associated with a number of autoimmune diseases, such as systemic lupus erythematosus. These are known as anti-nuclear antibodies (ANA) and have also been observed in concert with multiple sclerosis as part of general immune system dysfunction. As in the case of progeria, the role played by the antibodies in inducing the symptoms of autoimmune diseases is not obvious.
[edit] Nucleolus
The nucleolus is a discrete densely stained structure found in the nucleus. It is not surrounded by a membrane, and is sometimes called a suborganelle. It forms around tandem repeats of rDNA, DNA coding for ribosomal RNA (rRNA). These regions are called nucleolar organizer regions (NOR). The main roles of the nucleolus are to synthesize rRNA and assemble ribosomes. The structural cohesion of the nucleolus depends on its activity, as ribosomal assembly in the nucleolus results in the transient association of nucleolar components, facilitating further ribosomal assembly, and hence further association. This model is supported by observations that inactivation of rDNA results in intermingling of nucleolar structures.
The first step in ribosomal assembly is transcription of the rDNA, by a protein called RNA polymerase I, forming a large pre-rRNA precursor. This is cleaved into the subunits 5.8S, 18S, and 28S rRNA. The transcription, post-transcriptional processing, and assembly of rRNA occurs in the nucleolus, aided by small nucleolar RNA (snoRNA) molecules, some of which are derived from spliced introns from messenger RNAs encoding genes related to ribosomal function. The assembled ribosomal subunits are the largest structures passed through the nuclear pores.
When observed under the electron microscope, the nucleolus can be seen to consist of three distinguishable regions: the innermost fibrillar centers (FCs), surrounded by the dense fibrillar component (DFC), which in turn is bordered by the granular component (GC). Transcription of the rDNA occurs either in the FC or at the FC-DFC boundary, and therefore when rDNA transcription in the cell is increased more FCs are detected. Most of the cleavage and modification of rRNAs occurs in the DFC, while the latter steps involving protein assembly onto the ribosomal subunits occurs in the GC.
[edit] Other subnuclear bodies
Besides the nucleolus, the nucleus contains a number of other non-membrane delineated bodies. These include Cajal bodies, Gemini of coiled bodies, polymorphic interphase karyosomal association (PIKA), promyelocytic leukaemia (PML) bodies, paraspeckles and splicing speckles. Although little is known about a number of these domains, they are significant in that they show that the nucleoplasm is not uniform mixture, but rather contains organized functional subdomains.
Other subnuclear structures appear as part of abnormal disease processes. For example, the presence of small intranuclear rods have been reported in some cases of nemaline myopathy. This condition typically results from mutations in actin, and the rods themselves consist of mutant actin as well as other cytoskeletal proteins.
[edit] Cajal bodies and gems
A nucleus typically contains between 1 and 10 compact structures called Cajal bodies or coiled bodies (CB), whose diameter measures between 0.2�µm and 2.0�µm depending on the cell type and species. When seen under an electron microscope, they resemble balls of tangled thread and are dense foci of distribution for the protein coilin. CBs are involved in a number of different roles relating to RNA processing, specifically small nucleolar RNA (snoRNA) and small nuclear RNA (snRNA) maturation, and histone mRNA modification.
Similar to Cajal bodies are Gemini of coiled bodies, or gems, whose name is derived from the Gemini constellation in reference to their close "twin" relationship with CBs. Gems are similar in size and shape to CBs, and in fact are virtually indistinguishable under the microscope. Unlike CBs, gems do not contain small nuclear ribonucleoproteins (snRNPs), but do contain a protein called survivor of motor neurons (SMN) whose function relates to snRNP biogenesis. Gems are believed to assist CBs in snRNP biogenesis, though it has also been suggested from microscopy evidence that CBs and gems are different manifestations of the same structure.
[edit] PIKA and PTF domains
PIKA domains, or polymorphic interphase karyosomal associations, were first described in microscopy studies in 1991. Their function was and remains unclear, though they were not thought to be associated with active DNA replication, transcription, or RNA processing. They have been found to often associate with discrete domains defined by dense localization of the transcription factor PTF, which promotes transcription of snRNA.
[edit] PML bodies
Promyelocytic leukaemia bodies (PML bodies) are spherical bodies found scattered throughout the nucleoplasm, measuring around 0.2–1.0�µm. They are known by a number of other names, including nuclear domain 10 (ND10), Kremer bodies, and PML oncogenic domains. They are often seen in the nucleus in association with Cajal bodies and cleavage bodies. It has been suggested that they play a role in regulating transcription.
[edit] Paraspeckles
Discovered by Fox et al. in 2002, paraspeckles are irregularly shaped compartments in the nucleus' interchromatin space. First documented in HeLa cells, where there are generally 10–30 per nucleus, paraspeckles are now known to also exist in all human primary cells, transformed cell lines and tissue sections. Their name is derived from their distribution in the nucleus; the "para" is short for parallel and the "speckles" refers to the splicing speckles to which they are always in close proximity.
Paraspeckles are dynamic structures that are altered in response to changes in cellular metabolic activity. They are transcription dependent and in the absence of RNA Pol II transcription, the paraspeckle disappears and all of its associated protein components (PSP1, p54nrb, PSP2, CFI(m)68 and PSF) form a crescent shaped perinucleolar cap in the nucleolus. This phenomenon is demonstrated during the cell cycle. In the cell cycle, paraspeckles are present during interphase and during all of mitosis except for telophase. During telophase, when the two daughter nuclei are formed, there is no RNA Pol II transcription so the protein components instead form a perinucleolar cap.
[edit] Splicing speckles
Sometimes referred to as interchromatin granule clusters or as splicing-factor compartments, speckles are rich in splicing snRNPs and other splicing proteins necessary for pre-mRNA processing. Because of a cell's changing requirements, the composition and location of these bodies changes according to mRNA transcription and regulation via phosphorylation of specific proteins.
[edit] Function
The main function of the cell nucleus is to control gene expression and mediate the replication of DNA during the cell cycle. The nucleus provides a site for genetic transcription that is segregated from the location of translation in the cytoplasm, allowing levels of gene regulation that are not available to prokaryotes.
[edit] Cell compartmentalization
The nuclear envelope allows the nucleus to control its contents, and separate them from the rest of the cytoplasm where necessary. This is important for controlling processes on either side of the nuclear membrane. In some cases where a cytoplasmic process needs to be restricted, a key participant is removed to the nucleus, where it interacts with transcription factors to downregulate the production of certain enzymes in the pathway. This regulatory mechanism occurs in the case of glycolysis, a cellular pathway for breaking down glucose to produce energy. Hexokinase is an enzyme responsible for the first the step of glycolysis, forming glucose-6-phosphate from glucose. At high concentrations of fructose-6-phosphate, a molecule made later from glucose-6-phosphate, a regulator protein removes hexokinase to the nucleus, where it forms a transcriptional repressor complex with nuclear proteins to reduce the expression of genes involved in glycolysis.
In order to control which genes are being transcribed, the cell separates some transcription factor proteins responsible for regulating gene expression from physical access to the DNA until they are activated by other signaling pathways. This prevents even low levels of inappropriate gene expression. For example in the case of NF-κB-controlled genes, which are involved in most inflammatory responses, transcription is induced in response to a signal pathway such as that initiated by the signaling molecule TNF-α, binds to a cell membrane receptor, resulting in the recruitment of signalling proteins, and eventually activating the transcription factor NF-κB. A nuclear localisation signal on the NF-κB protein allows it to be transported through the nuclear pore and into the nucleus, where it stimulates the transcription of the target genes.
The compartmentalization allows the cell to prevent translation of unspliced mRNA. Eukaryotic mRNA contains introns that must be removed before being translated to produce functional proteins. The splicing is done inside the nucleus before the mRNA can be accessed by ribosomes for translation. Without the nucleus ribosomes would translate newly transcribed (unprocessed) mRNA resulting in misformed and nonfunctional proteins.
[edit] Gene expression
Gene expression first involves transcription, in which DNA is used as a template to produce RNA. In the case of genes encoding proteins, that RNA produced from this process is messenger RNA (mRNA), which then needs to be translated by ribosomes to form a protein. As ribosomes are located outside the nucleus, mRNA produced needs to be exported.
Since the nucleus is the site of transcription, it also contains a variety of proteins which either directly mediate transcription or are involved in regulating the process. These proteins include helicases that unwind the double-stranded DNA molecule to facilitate access to it, RNA polymerases that synthesize the growing RNA molecule, topoisomerases that change the amount of supercoiling in DNA, helping it wind and unwind, as well as a large variety of transcription factors that regulate expression.
[edit] Processing of pre-mRNA
Newly synthesized mRNA molecules are known as primary transcripts or pre-mRNA. They must undergo post-transcriptional modification in the nucleus before being exported to the cytoplasm; mRNA that appears in the nucleus without these modifications is degraded rather than used for protein translation. The three main modifications are 5' capping, 3' polyadenylation, and RNA splicing. While in the nucleus, pre-mRNA is associated with a variety of proteins in complexes known as heterogeneous ribonucleoprotein particles (hnRNPs). Addition of the 5' cap occurs co-transcriptionally and is the first step in post-transcriptional modification. The 3' poly-adenine tail is only added after transcription is complete.
RNA splicing, carried out by a complex called the spliceosome, is the process by which introns, or regions of DNA that do not code for protein, are removed from the pre-mRNA and the remaining exons connected to re-form a single continuous molecule. This process normally occurs after 5' capping and 3' polyadenylation but can begin before synthesis is complete in transcripts with many exons. Many pre-mRNAs, including those encoding antibodies, can be spliced in multiple ways to produce different mature mRNAs that encode different protein sequences. This process is known as alternative splicing, and allows production of a large variety of proteins from a limited amount of DNA.
[edit] Dynamics and regulation
[edit] Nuclear transport
The entry and exit of large molecules from the nucleus is tightly controlled by the nuclear pore complexes. Although small molecules can enter the nucleus without regulation, macromolecules such as RNA and proteins require association karyopherins called importins to enter the nucleus and exportins to exit. "Cargo" proteins that must be translocated from the cytoplasm to the nucleus contain short amino acid sequences known as nuclear localization signals which are bound by importins, while those transported from the nucleus to the cytoplasm carry nuclear export signals bound by exportins. The ability of importins and exportins to transport their cargo is regulated by GTPases, enzymes that hydrolyze the molecule guanosine triphosphate to release energy. The key GTPase in nuclear transport is Ran, which can bind either GTP or GDP (guanosine diphosphate) depending on whether it is located in the nucleus or the cytoplasm. Whereas importins depend on RanGTP to dissociate from their cargo, exportins require RanGTP in order to bind to their cargo.
Nuclear import depends on the importin binding its cargo in the cytoplasm and carrying it through the nuclear pore into the nucleus. Inside the nucleus, RanGTP acts to separate the cargo from the importin, allowing the importin to exit the nucleus and be reused. Nuclear export is similar, as the exportin binds the cargo inside the nucleus in a process facilitated by RanGTP, exits through the nuclear pore, and separates from its cargo in the cytoplasm.
Specialized export proteins exist for translocation of mature mRNA and tRNA to the cytoplasm after post-transcriptional modification is complete. This quality-control mechanism is important due to the these molecules' central role in protein translation; mis-expression of a protein due to incomplete excision of exons or mis-incorporation of amino acids could have negative consequences for the cell; thus incompletely modified RNA that reaches the cytoplasm is degraded rather than used in translation.
[edit] Assembly and disassembly
During its lifetime a nucleus may be broken down, either in the process of cell division or as a consequence of apoptosis, a regulated form of cell death. During these events, the structural components of the nucleus—the envelope and lamina—are systematically degraded.
During the cell cycle the cell divides to form two cells. In order for this process to be possible, each of the new daughter cells must have a full set of genes, a process requiring replication of the chromosomes as well as segregation of the separate sets. This occurs by the replicated chromosomes, the sister chromatids, attaching to microtubules, which in turn are attached to different centrosomes. The sister chromatids can then be pulled to separate locations in the cell. In many cells the centrosome is located in the cytoplasm, outside the nucleus, the microtubules would be unable to attach to the chromatids in the presence of the nuclear envelope. Therefore the early stages in the cell cycle, beginning in prophase and until around prometaphase, the nuclear membrane is dismantled. Likewise, during the same period, the nuclear lamina is also disassembled, a process regulated by phosphorylation of the lamins. Towards the end of the cell cycle, the nuclear membrane is reformed, and around the same time, the nuclear lamina are reassembled by dephosphorylating the lamins.
However, in dinoflagellates the nuclear envelope remains intact, the centrosomes are located in the cytoplasm, and the microtubules come in contact with chromosomes, whose centromeric regions are incorporated into the nuclear envelope (the so-called closed mitosis with extranuclear spindle). In many other protists (e.g. ciliates, sporozoans) and fungi the centrosomes are intranuclear, and their nuclear envelope also does not disassemle during cell division.
Apoptosis is a controlled process in which the cell's structural components are destroyed, resulting in death of the cell. Changes associated with apoptosis directly affect the nucleus and its contents, for example in the condensation of chromatin and the disintegration of the nuclear envelope and lamina. The destruction of the lamin networks is controlled by specialized apoptotic proteases called caspases, which cleave the lamin proteins and thus degrade the nucleus' structural integrity. Lamin cleavage is sometimes used as a laboratory indicator of caspase activity in assays for early apoptotic activity. Cells that express mutant caspase-resistant lamins are deficient in nuclear changes related to apoptosis, suggesting that lamins play a role in initiating the events that lead to apoptotic degradation of the nucleus. Inhibition of lamin assembly itself is an inducer of apoptosis.
The nuclear envelope acts as a barrier that prevents both DNA and RNA viruses from entering the nucleus. Some viruses require access to proteins inside the nucleus in order to replicate and/or assemble. DNA viruses, such as herpesvirus replicate and assemble in the cell nucleus, and exit by budding through the inner nuclear membrane. This process is accompanied by disassembly of the lamina on the nuclear face of the inner membrane.
[edit] Anucleated and polynucleated cells
Although most cells have a single nucleus, some eukaryotic cell types have no nucleus, and others have many nuclei. This can be a normal process, as in the maturation of mammalian red blood cells, or a result of faulty cell division.
Anucleated cells contain no nucleus and are therefore incapable of dividing to produce daughter cells. The best-known anucleated cell is the mammalian red blood cell, or erythrocyte, which also lacks other organelles such as mitochondria and serves primarily as a transport vessel to ferry oxygen from the lungs to the body's tissues. Erythrocytes mature through erythropoiesis in the bone marrow, where they lose their nuclei, organelles, and ribosomes. The nucleus is expelled during the process of differentiation from an erythroblast to a reticulocyte, which is the immediate precursor of the mature erythrocyte. The presence of mutagens may induce the release of some immature "micronucleated" erythrocytes into the bloodstream. Anucleated cells can also arise from flawed cell division in which one daughter lacks a nucleus and the other has two nuclei.
Polynucleated cells contain multiple nuclei. Most Acantharean species of protozoa and some fungi in mycorrhizae have naturally polynucleated cells. Other examples include the intestinal parasites in the genus Giardia, which have two nuclei per cell. In humans, skeletal muscle cells, called myocytes, become polynucleated during development; the resulting arrangement of nuclei near the periphery of the cells allows maximal intracellular space for myofibrils. Multinucleated cells can also be abnormal in humans; for example, cells arising from the fusion of monocytes and macrophages, known as giant multinucleated cells, sometimes accompany inflammation and are also implicated in tumor formation.
[edit] Evolution
As the major defining characteristic of the eukaryotic cell, the nucleus' evolutionary origin has been the subject of much speculation. Four major theories have been proposed to explain the existence of the nucleus, although none have yet earned widespread support.
The theory known as the "syntrophic model" proposes that a symbiotic relationship between the archaea and bacteria created the nucleus-containing eukaryotic cell. It is hypothesized that the symbiosis originated when ancient archaea, similar to modern methanogenic archaea, invaded and lived within bacteria similar to modern myxobacteria, eventually forming the early nucleus. This theory is analogous to the accepted theory for the origin of eukaryotic mitochondria and chloroplasts, which are thought to have developed from a similar endosymbiotic relationship between proto-eukaryotes and aerobic bacteria. The archaeal origin of the nucleus is supported by observations that archaea and eukarya have similar genes for certain proteins, including histones. Observations that myxobacteria are motile, can form multicellular complexes, and possess kinases and G proteins similar to eukarya, support a bacterial origin for the eukaryotic cell.
A second model proposes that proto-eukaryotic cells evolved from bacteria without an endosymbiotic stage. This model is based on the existence of modern planctomycetes bacteria that possess a nuclear structure with primitive pores and other compartmentalized membrane structures. A similar proposal states that a eukaryote-like cell, the chronocyte, evolved first and phagocytosed archaea and bacteria to generate the nucleus and the eukaryotic cell.
The most controversial model, known as viral eukaryogenesis, posits that the membrane-bound nucleus, along with other eukaryotic features, originated from the infection of a prokaryote by a virus. The suggestion is based on similarities between eukaryotes and viruses such as linear DNA strands, mRNA capping, and tight binding to proteins (analogizing histones to viral envelopes). One version of the proposal suggests that the nucleus evolved in concert with phagocytosis to form an early cellular "predator". Another variant proposes that eukaryotes originated from early archaea infected by poxviruses, on the basis of observed similarity between the DNA polymerases in modern poxviruses and eukaryotes. It has been suggested that the unresolved question of the evolution of sex could be related to the viral eukaryogenesis hypothesis.
Finally, a very recent proposal suggests that traditional variants of the endosymbiont theory are insufficiently powerful to explain the origin of the eukaryotic nucleus. This model, termed the exomembrane hypothesis, suggests that the nucleus instead originated from a single ancestral cell that evolved a second exterior cell membrane; the interior membrane enclosing the original cell then became the nuclear membrane and evolved increasingly elaborate pore structures for passage of internally synthesized cellular components such as ribosomal subunits.

Summary:
In cell biology, the nucleus (pl. nuclei; from Latin nucleus or nuculeus, meaning kernel), also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these chromosomes are the cell's nuclear genome. The function of the nucleus is to maintain the integrity of these genes and to control the activities of the cell by regulating gene expression — the nucleus is therefore the control center of the cell. The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and separates its contents from the cellular cytoplasm, and the nuclear lamina, a meshwork within the nucleus that adds mechanical support, much like the cytoskeleton supports the cell as a whole. Because the nuclear membrane is impermeable to most molecules, nuclear pores are required to allow movement of molecules across the envelope. These pores cross both of the membranes, providing a channel that allows free movement of small molecules and ions. The movement of larger molecules such as proteins is carefully controlled, and requires active transport regulated by carrier proteins. Nuclear transport is crucial to cell function, as movement through the pores is required for both gene expression and chromosomal maintenance.
Although the interior of the nucleus does not contain any membrane-bound subcompartments, its contents are not uniform, and a number of subnuclear bodies exist, made up of unique proteins, RNA molecules, and particular parts of the chromosomes. The best known of these is the nucleolus, which is mainly involved in the assembly of ribosomes. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA.