Properties of a Drosophila RNA polymerase II elongation factor

We have purified from nuclear extracts of Drosophila Kc cells a 36-kDa protein, DmS-II, which has an effect on the elongation properties of RNA polymerase II. DmS-II stimulates RNA polymerase II during the transcription of double-stranded DNA templates when the nonphysiological divalent cation manganese is present. In the presence of physiological mono- and divalent cations, the factor reduces the tendency of RNA polymerase II to pause at specific sites along a dC-tailed template including the major pause encountered after 14 nucleotides have been incorporated. Based on its size and chromatographic properties, as well as its ability to stimulate RNA polymerase II activity in the presence of manganese, the protein seems to be analogous to a factor S-II purified from mouse cells (Sekimizu, K., Kobayashi, N., Mizuno, D., and Natori, S. (1976) Biochemistry 15, 5064-5070). We have used a completely defined system and show that the properties of DmS-II are intrinsic to the factor and not mediated through other factors.