[1] NCI, FREDERICK CANC RES & DEV CTR, MAMMALIAN GENET LAB, ABL BASIC RES PROGRAM, FREDERICK, MD 21702 USA
[2] UNIV LIEGE, INST CHIM B6, LAB BIOL MOL & GENIE GENET, B-4000 SART, BELGIUM
[3] UNIV GOTTINGEN, INST BIOCHEM & MOLEK BIOL, D-37073 GOTTINGEN, GERMANY
[4] ST JUDE CHILDRENS RES HOSP, DEPT BIOCHEM, MEMPHIS, TN 38105 USA