Factors involved in specific transcription by mammalian RNA polymerase II. Transcription factor IIS stimulates elongation of RNA chains.

A factor that stimulates random transcription of purified DNAs by RNA polymerase II has been partially purified and analyzed with respect to its possible role in specific transcription from class II promoters. Studies of the effect of this factor (transcription factor IIS) on transcription from the adenovirus major late promoter in a system reconstituted with RNA polymerase II and purified factors (IIA, IIB, IIE, and IID) indicated that it acted subsequent to the initiation step and that it stimulated the rate of elongation. Kinetic experiments indicated that the factor affected the efficiency with which the RNA polymerase II passed through pausing sites. The relationship of transcription factor IIS to a protein previously purified from Erlich ascites tumor cells (Sekimizu, K., Nakanishi, Y., Mizuno, D., and Natori, S. (1979) Biochemistry 18, 1582-1588) was also studied.