title: The asiA gene of bacteriophage T4 codes for the anti-sigma 70 protein.
abstract: The anti-sigma 70 factor of bacteriophage T4 is a 10-kDa (10K) protein which inhibits the sigma 70-directed initiation of transcription by Escherichia coli RNA polymerase holoenzyme. We have partially purified the anti-sigma 70 factor and obtained the sequence of a C-terminal peptide of this protein. Using reverse genetics, we have identified, at the end of the lysis gene t and downstream of an as yet unassigned phage T4 early promoter, an open reading frame encoding a 90-amino-acid protein with a predicted molecular weight of 10,590. This protein has been overproduced in a phage T7 expression system and partially purified. It shows a strong inhibitory activity towards sigma 70-directed transcription (by RNA polymerase holoenzyme), whereas it has no significant effect on sigma 70-independent transcription (by RNA polymerase core enzyme). At high ionic strength, this inhibition is fully antagonized by the neutral detergent Triton X-100. Our results corroborate the initial observations on the properties of the phage T4 10K anti-sigma 70 factor, and we therefore propose that the gene which we call asiA, identified in the present study, corresponds to the gene encoding this T4 transcriptional inhibitor.
authors.affiliation: CNRS Centre de Génétique Moléculaire, Université Pierre et Marie Curie, Gif-sur-Yvette, France.
authors.forename: G
authors.initials: G
authors.lastname: Orsini
authors.forename: M
authors.initials: M
authors.lastname: Ouhammouch
authors.forename: J P
authors.initials: JP
authors.lastname: Le Caer
authors.forename: E N
authors.initials: EN
authors.lastname: Brody
mesh_terms: D000595:Amino Acid Sequence; D017122:Bacteriophage T4 / Q000235:genetics*; D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral / Q000235:genetics*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016366:Open Reading Frames / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis; D012808:Sigma Factor / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification
chemical_list: C078876:AsiA protein, Enterobacteria phage T4; D011994:Recombinant Proteins; D012808:Sigma Factor; D014764:Viral Proteins; D012321:DNA-Directed RNA Polymerases