Reese Witherspoon as singer June Carter in "Walk the Line" and Philip Seymour Hoffman as author Truman Capote in "Capote" won lead-acting awards Sunday from the Screen Actors Guild, while the ensemble drama "Crash" pulled off an upset win over "Brokeback Mountain" for the overall cast award.

Rachel Weisz of the murder thriller "The Constant Gardener" and Paul Giamatti of the boxing drama "Cinderella Man" received supporting-acting honors.

"Oh, my God, y'all. Sometimes, I can't just shake the feeling that I'm just a little girl from Tennessee," said Witherspoon, who plays Carter during her long, stormy courtship with country legend Johnny Cash. "I want to say my biggest inspiration for this movie obviously was June Carter. She was an incredible woman."

Hoffman, considered the favorite for the best-actor Oscar as Capote amid the author's struggles to research and write the true-crime novel "In Cold Blood," had gushing thanks for his "Capote" co-stars.

"It's important to say that actors can't act alone, it's impossible. What we have to do is support each other," Hoffman said. "Actors have to have each others' backs. It's the only way to act well is when you know the other actor has your back, and these actors had my back, and I hope they know I had theirs."

"Brokeback Mountain" has been considered the best-picture front-runner at the Oscars, whose nominations come out Tuesday, with awards presented March 5. Its loss to "Crash" could prove a speed-bump on the film's path toward becoming the first explicitly gay-themed movie to win a best picture award at the Oscars, but "Brokeback Mountain" has dominated earlier Hollywood honors so it will likely continue to be considered the favorite.

It led the Jan. 16 Golden Globes with four wins, among them best dramatic film and director for Ang Lee, who took the same prize Saturday from the Directors Guild of America.

Adapted from Annie Proulx's short story about old sheepherding buddies who conceal a homosexual affair from their families, "Brokeback Mountain" also has earned top honors from key critics groups and the Producers Guild of America.

Sean Hayes, won for best actor in a TV comedy for his role as a gay man in "Will & Grace," had a ready wisecrack about "Brokeback Mountain."

"First of all, I would like to thank Ang Lee for taking a chance on me," said Hayes, who is not in "Brokeback Mountain."

Last year, the wine-country romp "Sideways" won SAG's ensemble prize, while "Million Dollar Baby" went on to earn best-picture.

"Crash" follows the lives of a far-flung cast of characters over a chaotic 36-hour period in Los Angeles.

"This celebrates the definition of what an ensemble is all about. There's 74 of us," "Crash" co-star Terrence Howard said of the film's huge cast.

Weisz won supporting-actress for her role as a rabble-rousing humanitarian-aid worker, while Giamatti was honored as supporting actor for playing the manager of Depression-era fighter Jim Braddock. Both had gracious thanks for their fellow actors.

"I can't imagine a greater honor than being acknowledged by my peers," Giamatti said. "Being an actor is a hell of a thing. It's a hell of a thing. It's up and down. It's great, but I found the best thing about it is hanging around the craft-service table with other actors and crew people, eating doughnuts."

"It's so special to be honored by fellow actors, so thanks very much to the tribe," said Weisz, who also won the Golden Globe supporting-actress prize.

Felicity Huffman, who has been considered the best-actress Oscar front-runner for her gender-bending role in "Transamerica," lost to Witherspoon but won the guild prize for best actress in a TV comedy for "Desperate Housewives," which also won for best comedy ensemble.

"I love actors. I married one. OK, I married a fantastic one," Huffman said, of her husband, William H. Macy. "But even more than acting, I love the community of actors. I love the green room. I love the hair and makeup trailer. ... I'm so happy I can make a living at it, because I was never very good at math."

The best-actress honor for a television drama series went to Sandra Oh for the medical drama "Grey's Anatomy." Oh said she was gratified at how the casting of the show reflected real-world diversity.

"This is unbelievable. I thank every single actor out there. I'm so grateful for having a job," Oh said. "To all my fellow Asian-American actors out there, I share this with you, and be encouraged and keep shining."

Kiefer Sutherland won as best actor in a TV drama for the action series "24," while the airplane-disaster show "Lost" won for TV dramatic ensemble.

"A friend of mine always says if you don't have something nice to say about someone, say it," said "Lost" co-star Terry O'Quinn, surrounded by fellow cast members. "This is the saddest collection of climbing, grasping, paranoid, back-stabbing, screen-grabbing schmoozers and losers that you ever saw in your life. But we love each very much."