A mammalian SRB protein associated with an RNA polymerase II holoenzyme

Abstract

A LARGE multisubunit complex containing RNA polymerase II, general transcription factors and SRB regulatory proteins initiates transcription of class II genes in yeast cells1–4. The SRB proteins are a hallmark of this RNA polymerase II holoenzyme as they are found only in this complex, where they contribute to the response to regulators4–8. We have now isolated a human honiologue of the yeast SRB7 gene and used antibodies against human SRB7 protein to purify and characterize a mammalian RNA polymerase II holoenzyme containing the general transcription factors TFIIE and TFIIH. This holoenzyme is more responsive to transcriptional activators than core RNA polymerase II when assayed in the presence of coactivators.