FACTORS ASSOCIATED WITH THE MAMMALIAN RNA-POLYMERASE-II HOLOENZYME

The RNA polymerase II (Pol II) holoenzyme in yeast is an essential tra nscriptional regulatory complex which has been defined by genetic and biochemical approaches. The mammalian counterpart to this complex, how ever, is less well defined. Experiments herein demonstrate that, along with Pol II and SRB proteins, proteins associated with transcriptiona l regulation as cofactors are associated with the Pol II holoenzyme. E arlier experiments have demonstrated that the breast cancer-associated tumor suppressor BRCA1 and the CREB binding protein (CBP) were associ ated with the holoenzyme complex. The protein related to CBP, the E1A- associated p300 protein, is shown in these experiments to be associate d with the holoenzyme complex as well as the BRG1 subunit of the chrom atin remodeling SWI/SNF complex. Importantly the Pol II holoenzyme com plex does not contain some factors previously reported as stoichiometr ic components of the holoenzyme complex, most notably the proteins whi ch function in repair of damaged DNA, such as PCNA, RFC and RPA. The p resence of the p300 coactivator and the chromatin-modifying BRG1 prote in support a role for the Pol II holoenzyme as a key target for regula tion by enhancer binding proteins.