An RNA polymerase II transcription factor shares functional properties with Escherichia coli σ⁷⁰

A mammalian transcription factor, which, along with other factors, is essential for accurate initiation of transcription from promoters by RNA polymerase II, has been found to regulate the interaction of polymerase and DNA. This factor, designated βγ, drastically reduces the affinity of RNA polymerase II for free DNA containing either promoter or nonpromoter sequences. In this respect, βγ functions as does the bacterial transcription initiation factor σ⁷⁰, which expedites the binding of Escherichia coli RNA polymerase to promoters in part by accelerating dissociation of the polymerase from nonpromoter sites in DNA.