Figure 4.

Pol II subunits hRPB2 and hRPB10α mediate BRCA1-dependent transcriptional activation before initiation. All reactions were performed as in Fig. 2 except that UTP was excluded, stopping synthesis of the nascent transcript after incorporation of seven nucleotides. Individual Pol II subunits in concentrations identical to Fig. 2 were added concurrent with initiation of the reaction (I), or later upon resumption of transcript elongation by the addition of UTP (E).