A pathway branching in transcription initiation in Escherichia coli

Summary In transcription initiation, all RNA polymerase molecules bound to a promoter have been conventionally supposed to proceed into elongation of transcript. However, for Escherichia coli RNA polymerase, evidence has been accumulated for a view that only its fraction can proceed into elongation and the rest is retained at a promoter in non‐productive form: a pathway branching in transcription initiation. Proteins such as GreA and GreB affect these fractions at several promoters in vitro . To reveal the ubiquitous existence of the branched mechanism in E. coli , we searched for candidate genes whose transcription decreased by disruption of greA and greB using a DNA array. Among the arbitrarily selected 11 genes from over 100, the atpC , cspA and rpsA passed the test by Northern blotting. The Gre factors activated transcription initiation from their promoters in vitro , and the results demonstrated that the branched mechanism is exploited in vivo regulation. Consistently, decrease in the level of the GreA in an anaerobic stationary condition accompanied a decrease in the levels of transcripts of these genes.