title: Mutations affecting two adjacent amino acid residues in the alpha subunit of RNA polymerase block transcriptional activation by the bacteriophage P2 Ogr protein.
abstract: The bacteriophage P2 ogr gene product is a positive regulator of transcription from P2 late promoters. The ogr gene was originally defined by compensatory mutations that overcame the block to P2 growth imposed by a host mutation, rpoA109, in the gene encoding the alpha subunit of RNA polymerase. DNA sequence analysis has confirmed that this mutation affects the C-terminal region of the alpha subunit, changing a leucine residue at position 290 to a histidine (rpoAL290H). We have employed a reporter plasmid system to screen other, previously described, rpoA mutants for effects on activation of a P2 late promoter and have identified a second allele, rpoA155, that blocks P2 late transcription. This mutation lies just upstream of rpoAL290H, changing the leucine residue at position 289 to a phenylalanine (rpoAL289F). The effect of the rpoAL289F mutation is not suppressed by the rpoAL290H-compensatory P2 ogr mutation. P2 ogr mutants that overcome the block imposed by rpoAL289F were isolated and characterized. Our results are consistent with a direct interaction between Ogr and the alpha subunit of RNA polymerase and support a model in which transcription factor contact sites within the C terminus of alpha are discrete and tightly clustered.
authors.affiliation: Department of Microbiology, Virginia Commonwealth University, Richmond.
authors.forename: D J
authors.initials: DJ
authors.lastname: Ayers
authors.forename: M G
authors.initials: MG
authors.lastname: Sunshine
authors.forename: E W
authors.initials: EW
authors.lastname: Six
authors.forename: G E
authors.initials: GE
authors.lastname: Christie
mesh_terms: D000483:Alleles; D001483:Base Sequence; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D004755:Enterobacteriaceae / Q000201:enzymology / Q000235:genetics* / Q000821:virology; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000821:virology; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012486:Salmonella typhimurium / Q000201:enzymology / Q000235:genetics / Q000821:virology; D012641:Selection, Genetic; D017421:Sequence Analysis; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D014157:Transcription Factors; D014764:Viral Proteins; C074897:ogr protein, Enterobacteria phage P2; D012321:DNA-Directed RNA Polymerases