RNA polymerase in vegetative cells of Bacillus subtilis. II. New polypeptide factors, FI and FII, stimulating in vitro RNA synthesis directed by phage M2 DNA.

Two polypeptides named FI and FII were isolated from vegetative cells of Bacillus subtilis Marburg. The molecular weights of FI and FII were 15,000 and 30,000 daltons, respectively. They were able to stimulate the transcription of phage M2 DNA in the presence of Mg2+ ions by RPase L1 and RPase L2 [RNA polymerase; EC 2.7.7.6]. Although both core- and holo-RPase L2 hardly exhibited transcription activity under these conditions, the factors could stimulate both activities up to the level of RPase L1 activity. The stimulation was much less marked when B. subtilis DNA was used as a template. These stimulatory functions were found to lie not in the chain elongation but in the initiation step of transcription, following the preinitiation step. To obtain stimulation by the factors, preincubation with RNA polymerase was necessary. FI stimulated RPase L1 or RPase L2 only when preincubated in the stimultaneous presence of FII, forming a complex, RPase L1(or L2)-FI-FII. On the other hand, FII alone could stimulate transcription, forming a complex. RPase L1 (or L2)-FII. In these complexes, the ratio of FI, FII, and RPase L1(or L2) was 1 : 1: 1. Although the core-RPase L2 activity was inhibited by sigma subunits, it was not inhibited by was rather stimulated when the enzyme was present as a complex with FI and FII. Thus the complex, consisting of RPase L2 and the factors, resembled RPase L1 with respect to molecular weight, template specificity, the effect of sigma subunit, and sensitivity to rifampicin.