Author:
Schubert Rachel A.,Dodd Ian B.,Egan J. Barry,Shearwin Keith E.
Abstract
CI represses cro; Cro represses cI. This double negative feedback loop is the core of the classical CI–Cro epigenetic switch of bacteriophage λ. Despite the classical status of this switch, the role in λ development of Cro repression of the PRM promoter for CI has remained unclear. To address this, we created binding site mutations that strongly impaired Cro repression of PRM with only minimal effects on CI regulation of PRM. These mutations had little impact on λ development after infection but strongly inhibited the transition from lysogeny to the lytic pathway. We demonstrate that following inactivation of CI by ultraviolet treatment of lysogens, repression of PRM by Cro is needed to prevent synthesis of new CI that would otherwise significantly impede lytic development. Thus a bistable CI–Cro circuit reinforces the commitment to a developmental transition.
Publisher
Cold Spring Harbor Laboratory
Subject
Developmental Biology,Genetics
Cited by
86 articles.
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