BRCA1 interaction with RNA polymerase II reveals a role for hRPB2 and hRPB10 alpha in activated transcription

The functions of most of the 12 subunits of the RNA polymerase II (Pol II) enzyme are unknown. In this study, we demonstrate that two of the subunits, hRPB2 and hRPB10 alpha, mediate the regulated stimulation of transcription . We find that the transcriptional coactivator BRCA1 interacts directly wit h the core pol II complex in vitro. We tested whether single subunits from pal II would compete with the intact pol II complex to inhibit transcriptio n stimulated by BRCA1. Excess purified pol II subunits hRPB2 or hRPB10 alph a blocked BRCA1- and VP16-dependent transcriptional activation in vitro wit h minimal effect an basal transcription. No other pal fl subunits tested in hibited activated transcription in these assays. Furthermore, hRPB10 alpha, but not hRPB2, blocked Sp1-dependent activation.