The nature of transcription selectivity of bacteriophage SPO1-modified RNA polymerase

Escherichia coli and Bacillus subtilis RNA polymerase have almost identical transcription specificities on bacteriophage SPO1 DNA when assayed in a coupled transcription-translation cell free system. SPO1-modified B. subtilis RNA polymerase has altered transcription specificity. It is shown that rifampicin-inhibited E. coli RNA polymerase can completely block transcription of SPO1 DNA by rifampicin resistant B. subtilis enzyme, whereas it has no effect on transcription by SPO1-modified B. subtilis RNA polymerase. We conclude that the new transcription by SPO1-modified RNA polymerase results from newly recognized promoters, rather than by elongation of transcripts which could also be made by B. subtilis vegetative RNA polymerase.