Effect of the delta subunit of Bacillus subtilis RNA polymerase on initiation of RNA synthesis at two bacteriophage phi 29 promoters.

Initiation of RNA synthesis by Bacillus subtilis RNA polymerase (sigma-43) has been examined at two early promoters of phage phi 29: the A2 promoter, which is a weak promoter, and the G2 promoter, which is a strong promoter. The delta subunit of the polymerase inhibits the rate of initiation at A2, but not G2. In addition, formation of stable complexes by the polymerase at A2, but not at G2, requires the presence of the first two nucleotides of the A2 transcript.