Fifty Shades of Grey author E. L. James tweeted on Monday to announce who will play the leading roles for his book. James revealed Dakota Johnson to play Anastasia Steele and Charlie Hunnam to play the young billionaire Christian Grey.

Hunnam, most recently starred in science-fiction flick Pacific Rim. Johnson, the 23-year-old who made a cameo in The Office finale as Kevin's replacement, has had roles in Crazy in Alabama, 21 Jump Street, The Social Network and The Five-Year Engagement.

Fifty Shades of Grey centers on Christian's kinky relationship with recent college graduate Anastasia. Christian requires Anastasia to sign a sexual contract, and the two routinely engage in acts such as bondage.

The movie is slated for an Aug. 1, 2014, release by Universal Pictures and Focus Features.