Los Angeles ? 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.

“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 it has dominated earlier Hollywood honors, so it will likely continue to be considered the favorite.

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.

“We believe that it really celebrates the definition of what an ensemble is all about. I mean, there’s 74 of us,” “Crash” co-star Don Cheadle 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.

“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.

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.”

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.