On the role of Cro in λ prophage induction
- *National Cancer Institute, Bethesda, MD 20892-4255; and ‡National Cancer Institute, Frederick, MD 21702
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Contributed by Sankar Adhya, December 30, 2004
Abstract
The lysogenic state of bacteriophage λ is exceptionally stable yet the prophage is readily induced in response to DNA damage. This delicate epigenetic switch is believed to be regulated by two proteins; the lysogenic maintenance promoting protein CI and the early lytic protein Cro. First, we confirm, in the native configuration, the previous observation that the DNA loop mediated by oligomerization of CI bound to two distinct operator regions (O L and O R), increases repression of the early lytic promoters and is important for stable maintenance of lysogeny. Second, we show that the presence of the cro gene might be unimportant for the lysogenic to lytic switch during induction of the λ prophage. We revisit the idea that Cro's primary role in induction is instead to mediate weak repression of the early lytic promoters.
Footnotes
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↵ § To whom correspondence should be addressed at: Laboratory of Molecular Biology, 37 Convent Drive, Room 5138, National Cancer Institute, Bethesda, MD 20892-4264. E-mail: sadhya{at}helix.nih.gov.
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↵ † Present address: Department of Molecular Biology, Princeton University, Princeton, NJ 08544.
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Author contributions: S.L.S., N.C., D.L.C., and S.A. designed research; S.L.S., N.C., and S.A. performed research; S.L.S., N.C., D.L.C., and S.A. analyzed data; and S.L.S., D.L.C., and S.A. wrote the paper.
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Abbreviations: O R, operator right; O L, operator left; P R, promoter right; P L, promoter left; P RM, maintenance promoter.
