title: Sigma competition: the contest between bacteriophage T4 middle and late transcription.
abstract: In bacterial transcription, diverse sigma-family promoter recognition proteins compete for a common RNA polymerase core. Bacteriophage T4 infection ultimately reduces this competition to a duel between activated viral middle and enhanced late transcription, involving two sigma proteins, two phage-encoded activator proteins and two phage-specific co-activators. This competition has been analyzed in vitro, and the relative abundances in T4-infected Escherichia coli of the participating proteins have been measured. Activated late transcription holds an advantage over activated middle transcription, especially at higher ionic strength. This advantage is further compounded by ADP-ribosylation of the RNA polymerase alpha subunits, and by the phage-specific, RNA polymerase core-bound RpbA subunit. The largest contribution to the middle-late competition is made by gp55, the late sigma factor, but not enough of gp55 is produced during T4 infection to shut off middle transcription by direct competition with sigma(70). AsiA, the originally identified anti-sigma protein is not a major determinant of middle-late competition.
authors.affiliation: Department of Biology and Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0634, USA. skolesky@biomail.ucsd.edu
authors.forename: S
authors.initials: S
authors.lastname: Kolesky
authors.forename: M
authors.initials: M
authors.lastname: Ouhammouch
authors.forename: E N
authors.initials: EN
authors.lastname: Brody
authors.forename: E P
authors.initials: EP
authors.lastname: Geiduschek
mesh_terms: D000818:Animals; D017122:Bacteriophage T4 / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D009994:Osmolar Concentration; D011401:Promoter Regions, Genetic; D011817:Rabbits; D012808:Sigma Factor / Q000378:metabolism*; D013698:Templates, Genetic; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014764:Viral Proteins / Q000378:metabolism
chemical_list: C078876:AsiA protein, Enterobacteria phage T4; D004268:DNA-Binding Proteins; C067996:MotA protein, Enterobacteria phage T4; D012808:Sigma Factor; D015534:Trans-Activators; D014157:Transcription Factors; D014764:Viral Proteins; C085859:gene 33 protein, Enterobacteria phage T4; C074555:gene 45 protein, Enterobacteria phage T4; C106892:gene 55 protein, Enterobacteria phage T4; C091225:gene 59 protein, Enterobacteria phage T4; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases