"Sideways" star Paul Giamatti has given F. Gary Gray's N.W.A. biopic some real star power after signing on to playmusic mogul Jerry Heller in the film.

Heller, who represented Elton John, Pink Floyd and Journey, managed the rap act that featured Ice Cube and Dr. Dre.

He also founded Ruthless Records with N.W.A. star Eazy-E.

Giamatti joins producer Ice Cube's son O'Shea Jackson Jr. who will portray his dad in the movie, Straight Outta Compton, and other actors including Jason Mitchell and Corey Hawkins.

It's not the first time he'll play a ruthless music boss on the big screen - he portrayed Tom Cruise's slippery manager Paul Gill in "Rock of Ages."

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