The human homologue of Drosophila TRF-proximal protein is associated with an RNA polymerase II SRB complex

Mammalian RNA polymerase II holoenzymes are large complexes that have been reported to contain, in addition to RNA polymerase II, homologues of severa l yeast SRBs, various general transcription factors, and other polypeptides . On the basis of its copurification with an SRB-containing RNA polymerase II complex by conventional chromatography procedures, we have identified a human homologue of Drosophila TRF-proximal protein, designated hTRFP, and i solated its cognate cDNA Antibody specific for SRB7 can immunoprecipitate h TRFP and RNA polymerase II and, reciprocally, antibody specific for hTRFP c an immunoprecipitate RNA polymerase II and SRB7. These data indicate that h TRFP is an integral component of an RNA polymerase II-SRB complex. Whereas the precise function of hTRFP remains to be determined, the hTRFP-containin g RNA polymerase II-SRB complex supports basal level transcription and, rel ative to RNA polymerase II alone, enhances transcriptional activation by Ga 14-VP16 in the presence of cofactor PC4. Thus, hTRFP may regulate transcrip tion of class II genes through association with the RNA polymerase II-SRB c omplex.