λ represser regulates the switch between PR and Prm promoters

Abstract
The DNA region [of phage .lambda.] containing the QR operator, PR and Prm promoters and their transcription initiations is sequenced. By binding QR, repressor turns off PR, turns on Prm and at higher concentrations turns off Prm, regulating its own synthesis. Prm mRNA is unique in beginning immediately with the initiation of translation, without a preceding leader sequence.