[1] SALK INST BIOL STUDIES, GENE EXPRESS LAB, LA JOLLA, CA 92037 USA
[2] UNIV CALIF SAN DIEGO, DEPT BIOL, LA JOLLA, CA 92093 USA
[3] UNIV ILLINOIS, COLL MED, DEPT GENET, CHICAGO, IL 60612 USA
[4] UNIV TEXAS, HLTH SCI CTR, CANC THERAPY & RES CTR S TEXAS, SAN ANTONIO, TX 78284 USA