Credit: Diego Luna: George Pimentel/

Mexican actor Diego Luna (Y Tu Mama Tambien, The Night Buffalo) has joined the cast of director Gus Van Sant’s drama Milk, which stars Sean Penn as gay rights activist and former San Francisco politican Harvey Milk. Luna is playing Jack Lira, one of Milk’s supporters as well as his lover. He joins a cast that also includes Josh Brolin, Emile Hirsch, James Franco, Victor Garber, Denis O’Hare, and Stephen Spinella. The biopic will tell Milk’s story as the first openly gay elected official in America, voted to San Francisco’s city supervisors’ board in 1977. The following year, both he and Mayor George Moscone were assassinated by another city supervisor, Dan White. Luna’s breakout project was his starring role opposite Gael Garcia Bernal in 2001’s Y Tu Mama. He most recently appeared in last year’s Spanish-language thriller The Night Buffalo and the Harmony Korine-directed Mister Lonely.

–Additional reporting by Nicole Sperling.