[1] Univ Massachusetts, Med Ctr, Program Mol Med, Worcester, MA 01605 USA
[2] Univ Massachusetts, Med Ctr, Dept Biochem & Mol Biol, Worcester, MA 01605 USA
[3] Fred Hutchinson Canc Res Ctr, Seattle, WA 98109 USA
[4] Howard Hughes Med Inst, Seattle, WA 98109 USA
[5] Univ Washington, Mol & Cellular Biol Program, Fred Hutchinson Canc Res Ctr, Seattle, WA 98195 USA