Hexamethylene Bis Acetamide Inducible Protein 2 (HEXIM2)

HEXIM2, a previously predicted protein with sequence similarity to HEXIM1. Regulates positive transcription elongation factor b through association with 7SK. HEXIM2 is expressed in HeLa and Jurkat cells, and glycerol gradient analysis and immunoprecipitations indicate that HEXIM2, like HEXIM1, has a regulated association with P-TEFb. As HEXIM1 is knocked down, HEXIM2 functionally compensates for its association with P-TEFb. Electrophoretic mobility shift assays and in vitro kinase assays demonstrate that HEXIM2 forms complexes containing 7SK and P-TEFb and, in conjunction with 7SK, inhibits P-TEFb kinase activity.HEXIM2 is a regulator of P-TEFb function. The utilization of HEXIM1 or HEXIM2 to bind and inhibit P-TEFb can be differentially regulated in vivo.