Stimulation of RNA synthesis by two protein factors in extracts of Escherichia coli.

Two separate protein factors that markedly stimulate DNA-dependent RNA polymerase have been partially purified from ribosome-free extracts of E. coli Q13 cells. These proteins appear to differ from sigma, M, H, psi, and the factor described by Mahadik and Srinivasan. The stimulation by either factor requires the presence of the sigma protein. Using RNA-DNA hybridization competition analyses, we also demonstrate that neither of the new factors preferentially stimulates the synthesis of ribosomal RNA. The purification, properties, and mechanism of action of these new factors are examined.