Rapper/actor Mos Def will play rock n’ roll icon Chuck Berry for Sony BMG’s Cadillac Records, says The Hollywood Reporter. Gabrielle Union has also joined the film’s cast. She will portray Geneva Wade, a girlfriend of Muddy Waters. Written and directed by Darnell Martin, Cadillac Records “follows the turbulent but exciting lives of Leonard Chess, who founded Chess Records, and the label’s artists, including Waters, Little Walter and Howlin’ Wolf.”