[1] Canc Res UK, London Res Inst, Signal Transduct Lab, London WC2A 3PX, England
[2] Canc Res UK, London Res Inst, Prot Sequencing Lab, London WC2A 3PX, England
[3] Hosp Sick Children, Div Hematol Oncol, Toronto, ON M5G 1X8, Canada
[4] CUNY Mt Sinai Sch Med, Dept Biochem & Mol Biol, New York, NY 10029 USA