On the Role of Cro in λ Prophage Induction

• Published in: Proceedings of the National Academy of Sciences - PNAS 2005-03, Vol.102 (12), p.4465-4469
• Main Authors: Svenningsen, Sine L., Costantino, Nina, Court, Donald L., Adhya, Sankar
• Format: Article
• Language: English
• Subjects: Bacteriophage lambda - genetics; Bacteriophage lambda - physiology; Bacteriophages; Biological Sciences; Chromosome Mapping; Codons; DNA, Viral - chemistry; DNA, Viral - genetics; DNA-Binding Proteins - genetics; DNA-Binding Proteins - physiology; Epigenesis, Genetic; Escherichia coli K12 - virology; Genes; Genes, Reporter; Genes, Viral; Genetics; Immunity; Low temperature; Lysogeny; Lysogeny - genetics; Lysogeny - physiology; Operator regions; Phage l; Promoter Regions, Genetic; Prophages; Proteins; Reporter genes; Repression; Repressor Proteins - genetics; Repressor Proteins - physiology; Viral Proteins - genetics; Viral Proteins - physiology; Viral Regulatory and Accessory Proteins; Virus Activation - genetics; Virus Activation - physiology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0409839102

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 (OLand OR), 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.