title: Polarity within pM and pE promoted phage lambda cI-rexA-rexB transcription and its suppression.
abstract: The cI-rexA-rexB operon of bacteriophage lambda confers 2 phenotypes, Imm and Rex, to lysogenic cells. Immunity to homoimmune infecting lambda phage depends upon the CI repressor. Rex exclusion of T4rII mutants requires RexA and RexB proteins. Both Imm and Rex share temperature-sensitive conditional phenotypes when expressed from cI[Ts]857 but not from cI+ lambda prophage. Plasmids were made in which cI-rexA-rexB was transcribed from a non-lambda promoter, pTet. The cI857-rexA-rexB plasmid exhibited Ts conditional Rex and CI phenotypes; the cI+-rexA-rexB plasmid did not. Polarity was observed within cI-rexA-rexB transcription at sites in cI and rexA when CI was nonfunctional. Renaturation of the Ts CI857 repressor, allowing it to regain functionality, suppressed the polar effect on downstream transcription from the site in cI. The second strong polar effect near the distal end of rexA was observed for transcription initiated from pE. The introduction of a rho Ts mutation into the host genome suppressed both polar effects, as measured by its suppression of the conditional Rex phenotype. Strong suppression of the conditional Rex[Ts] phenotype was imparted by ssrA and clpP (polar for clpX) null mutations, suggesting that RexA or RexB proteins made under conditions of polarity are subject to 10Sa RNA tagging and ClpXP degradation.
authors.affiliation: Department of Microbiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada. hayess@duke.usask.ca
authors.forename: Sidney
authors.initials: S
authors.lastname: Hayes
authors.forename: Roderick A
authors.initials: RA
authors.lastname: Slavcev
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics* / Q000502:physiology; D018388:Codon, Terminator; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D049071:Endopeptidase Clp / Q000378:metabolism; D004926:Escherichia coli / Q000821:virology; D029968:Escherichia coli Proteins / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D008242:Lysogeny; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D018388:Codon, Terminator; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D012097:Repressor Proteins; C094107:RexA protein, Bacteriophage lambda; D017361:Viral Nonstructural Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; C069331:rexB protein, Bacteriophage lambda; C483573:ClpXP protease, E coli; D049071:Endopeptidase Clp