title: The Tum protein of coliphage 186 is an antirepressor.
abstract: The tum gene of coliphage 186, encoded on a LexA controlled operon, is essential for UV induction of a 186 prophage. Primer extension analysis is used to confirm that Tum is the sole phage function required for prophage induction and that it acts against the maintenance repressor, CI, to relieve repression of the lytic promoters, pR and pB, and thereby bring about lytic development. In vitro experiments with purified proteins demonstrate that Tum prevents CI binding to its operator sites. Tum does not compete with CI for binding sites on DNA, and unlike RecA mediated induction of lambda prophage, the action of Tum on CI is reversible. Mechanisms by which Tum may act against CI are discussed.
authors.affiliation: Department of Biochemistry, University of Adelaide, Adelaide 5005, Australia.
authors.forename: K E
authors.initials: KE
authors.lastname: Shearwin
authors.forename: A M
authors.initials: AM
authors.lastname: Brumby
authors.forename: J B
authors.initials: JB
authors.lastname: Egan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D019281:Dimerization; D015967:Gene Expression Regulation, Viral / Q000235:genetics; D007544:Isopropyl Thiogalactoside / Q000494:pharmacology; D009875:Operator Regions, Genetic / Q000235:genetics; D011487:Protein Conformation; D012097:Repressor Proteins / Q000037:antagonists & inhibitors*; D013014:SOS Response, Genetics / Q000235:genetics; D012697:Serine Endopeptidases / Q000235:genetics; D014466:Ultraviolet Rays / Q000009:adverse effects; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D054334:Viral Regulatory and Accessory Proteins; D014775:Virus Activation / Q000235:genetics; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D007544:Isopropyl Thiogalactoside; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; D000099160:LexA Repressor Protein; C016649:phage repressor proteins; C099332:tum protein, Enterobacteria phage 186