title: Mutants in the y region of bacteriophage lambda constitutive for repressor synthesis: their isolation and the characterization of the Hyp phenotype.
abstract: Bacteriophage lambdahyp mutants have been isolated as survivors of Escherichia coli K-12 bacteria lysogenic for lambda Nam7am53cI857. The hyp mutants are characterized by (i) their localization in the y region very close to the imm lambda/imm434 boundary, (ii) polarity on O gene expression, (iii) immediate recovery of lambda immunity at 30 degrees C after prolonged growth of lambda Nam7am53cI857 hyp lysogens at 42 degrees C even in the presence of an active cro gene product, (iv) ability of phage lambda v2v3vs326 but not lambda v1v2v3 to propagate on lambda cI+hyp lysogens, (v) inability to express lambda exonuclease activity after prophage induction, and (vi) inviability at any temperature of phage carrying the hyp mutation. All these properties are referred to collectively as the Hyp phenotype. We show that the Hyp phenotype is due to cII-independent constitutive cI-gene-product synthesis originating in the y region, which results in the synthesis of anti-cro RNA species, and constitutive levels of cro gene product present even in lambda cI+hyp lysogens. A model is presented which is consistent with all the experimental observations.
mesh_terms: D000956:Antigens, Viral / Q000235:genetics; D010582:Bacteriophage lambda / Q000235:genetics* / Q000276:immunology; D004268:DNA-Binding Proteins; D005092:Exonucleases / Q000096:biosynthesis; D005814:Genes, Viral; D009154:Mutation; D009876:Operon; D010641:Phenotype; D012367:RNA, Viral / Q000096:biosynthesis; D012097:Repressor Proteins / Q000235:genetics; D014158:Transcription, Genetic; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D000956:Antigens, Viral; D004268:DNA-Binding Proteins; D012367:RNA, Viral; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D005092:Exonucleases