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.