Involvement of the Escherichia coli RNA polymerase α subunit in transcriptional activation by the bacteriophage lambda CI and CII proteins

Abstract Escherichia coli cells harbouring the rpoA 341 mutation produce an RNA polymerase which transcribes inefficiently certain operons subject to positive control. Here, we demonstrate that the rpoA 41 allele also prevents lysogenization of the host strain by bacteriophage λ, a process dependent upon the action of two phage-encoded activators. This phenomenon was shown to arise from an inability to establish an integrated prophage rather than a failure to maintain the lysogenic state. The inability of the rpoA 341 host to support lysogenization could be completely reversed by CII-independent expression of int and cI in trans . These results led us to propose that the inhibition of lysogenization arises from a defective interaction between the phage λ transcriptional activator CII and the mutant RNA polymerase at the phage promoters p I and p E . Finally, we also provide genetic evidence for impaired transcription of the cI gene from the CI-activated promoter, p M in the rpoA 341 background.