Heat-sensitive lambda repressors retain partial activity during bacteriophage induction.
At 43 degrees C, lambda cIts prophages are "induced" and enter the lytic cycle. Lac- lysogens containing heat-inducible lambda N- prophages were superinfected with a lambda trp/lac N+cI- phage containing a lacZ+ gene whose expression is controlled by the lambda cI product (repressor). Lysogens were then heated, and the synthesis of beta-galactosidase and release of progeny phage were measured. In lambda N- cIts2 or lambda N-cIts16 lysogens superinfected with lambda trp/lac N+, beta-galactosidase appeared earlier and was synthesized more rapidly than in superinfected lysogens containing lambda N- cIts857 prophage. Even at 45 degrees C, the cI857 repressor retained some activity. Lysogens containing other N-cIts mutant prophages producing renaturable repressors were also only partially derepressed at 43 degrees C. Partial derepression of lambda "early" transcription is sufficient for induction of lambda N+ prophages.
D010582:Bacteriophage lambda / Q000235:genetics* / Q000254:growth & development; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005814:Genes, Viral; D006358:Hot Temperature; D007763:Lac Operon; D008242:Lysogeny; D009154:Mutation; D012097:Repressor Proteins / Q000096:biosynthesis*; D014157:Transcription Factors / Q000096:biosynthesis*; D014779:Virus Replication; D001616:beta-Galactosidase / Q000096:biosynthesis
D012097:Repressor Proteins; D014157:Transcription Factors; D001616:beta-Galactosidase