title: The cyanobacterial principal sigma factor region 1.1 is involved in DNA-binding in the free form and in transcription activity as holoenzyme.
abstract: Cyanobacterial principal sigma factor, sigma(A), includes a specifically conserved cluster of basic amino acids in the amino-terminal extension called region 1.1. We found that the sigma(A) in a thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 binds DNA in the absence of the core RNA polymerase and that sigma(A) lacking region 1.1 is not able to bind DNA. This indicates that, in the cyanobacterium, region 1.1 participates in DNA-binding, rather than inhibiting the interaction between free sigma and DNA, as found in other principal sigma factors of eubacteria. The results of in vitro transcription assays with the reconstituted RNA polymerase showed that region 1.1 reduces transcription activity from the cpc promoter.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Imashimizu
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Hanaoka
authors.forename: Asako
authors.initials: A
authors.lastname: Seki
authors.forename: Katsuhiko S
authors.initials: KS
authors.lastname: Murakami
authors.forename: Kan
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012808:Sigma Factor / Q000378:metabolism*; D046940:Synechococcus / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D012808:Sigma Factor