BREAKING… Gossip Girl’s Penn Badgley and CSI: NY’s Hill Harper have signed on for Parts Per Billion. Teresa Palmer and Alexis Bledel have also joined the Brian Horiuchi-directed and -written drama, which follows three separate couples as they deal with an event that threatens to destroy their relationships. Frank Langella, Gena Rowlands, Rosario Dawson and Josh Hartnett star. The recently created AKA/Bow Street Films is producing; Dawson is executive producing with Joe Jenckes, Cotty Chubb, Arianne Fraser and D. Todd Shepherd and George Waud. Molly Hassell, Jennifer Levine, Michael Benaroya and David Dickson are producing. Parts Per Billion is shooting in Detroit until the end of the year. Harper is repped by Innovative Artists and Luber Roklin Entertainment. Badgley, who stars in Greetings From Tim Buckley, out next year, is repped by CAA and Anonymous Content.