title: Role of the sigma factor in transcription initiation in the absence of core RNA polymerase.
abstract: Sigma factors (sigmas) are bacterial transcription factors that bind core RNA polymerase (RNAP) and direct transcription initiation at cognate promoter sites. However, most of their functions have been investigated in the context of RNAP. This has made the exact function of sigma, and the importance of core RNAP in modulating sigma function, ambiguous. Here we identify a Bacillus subtilis mutant sigma(A) that is independently capable of specific binding and melting of the promoter DNA. Interestingly, specific and independent promoter binding of sigma is sufficient for the temperature- and Mg(2+)-independent melting of promoter DNA around the transcription start site, in contrast to the temperature- and Mg(2+)-dependent melting by RNAP around the promoter -10 element. Thus core RNAP is able to negatively modulate the sigma-initiated melting of the transcription start site and, by sensing the changes in temperature and Mg(2+) concentration, to regulate the efficiency of promoter -10 melting.
authors.affiliation: Institute of Biochemistry, National Chung-Hsing University, Taichung 40227, Taiwan, Republic of China.
authors.forename: Hsin-Hsien
authors.initials: HH
authors.lastname: Hsu
authors.forename: Kuei-Min
authors.initials: KM
authors.lastname: Chung
authors.forename: Tsung-Ching
authors.initials: TC
authors.lastname: Chen
authors.forename: Ban-Yang
authors.initials: BY
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D024322:Amino Acids, Aromatic / Q000737:chemistry; D017103:Bacillus Phages / Q000235:genetics; D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D008274:Magnesium / Q000737:chemistry; D008969:Molecular Sequence Data; D009154:Mutation; D009691:Nucleic Acid Denaturation; D011401:Promoter Regions, Genetic / Q000502:physiology; D012045:Regulatory Sequences, Nucleic Acid; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013696:Temperature; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
chemical_list: D024322:Amino Acids, Aromatic; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004279:DNA, Viral; D012808:Sigma Factor; D012321:DNA-Directed RNA Polymerases; D008274:Magnesium