The interaction of Escherichia coli core RNA polymerase with specificity-determining subunits derived from unmodified...

the ability of the core isolated from Escherichia coli RNA polymerase to interact with specificity-determining subunits isolated from Bacillus subtilis RNA polymerase has been determined by measuring the transcription of "early" and "middle" genes of phage SP82. Two specificity-determining subunits were tested: the sigma subunit and a 28,000 dalton (28 K) peptide isolated from a modified polymerase produced at approximately 8 min after infection of B. subtilis with SP82. Earlier experiments (Spiegelman, G. B. and Whiteley, H. R. (1978) Biochem. Biophys. Res. Commun. 81, 1058-1065) demonstrated that sigma and the 28K peptide are required for the recognition of early and middle gene promoters, respectively, by the B. subtilis core assembly. The present investigation showed that E. coli core interacted more efficiently with the B. subtilis sigma than with the 28K peptide, as judged by the rate of RNA synthesis. Early RNA was produced by the E. coli and B. subtilis holoenzymes and by E. coli core supplenented with B. subtilis sigma and only minor differences were found in comparisons of transcripts by hybridization and by electrophoretic analysis. Measurements of template specificity, the formation of stable enzyme . DNA complexes, and the hybridization of transcripts to fragments of SP82 DNA produced by digestion with restriction endonuclease Hha indicated that E. coli core supplemented with the 28K-supplemented E. coli core with those synthesized by the modified polymerase extracted from B. subtilis 8 min after infection with SP82 suggest that both preparations recognized the same initiation and termination sequences.