title: Transcriptional activator C protein-mediated unwinding of DNA as a possible mechanism for mom gene activation.
abstract: The bacteriophage Mu mom gene encodes the unique DNA-modification function of the phage. Regulation of the mom gene at the transcriptional level is brought about by the transactivator protein C of the phage. The mom promoter is an activator-dependent weak promoter having poor -10 and -35 elements separated by a 19 bp suboptimal spacer region. These features could constrain RNA polymerase occupancy at the promoter. Here, we have probed into the mechanism by which C protein acts as a transcriptional activator at Pmom. In vivo dimethyl sulfate footprinting studies demonstrate C protein-mediated asymmetric distortion of its specific site at the mom regulatory region. Using a coupled topoisomerase assay, we demonstrate that C protein induces the unwinding of DNA. This C-mediated unwinding seems to be localised to the 3' flanking region of the C binding site located adjacent to and overlapping the -35 element of Pmom. These results suggest that C protein-mediated torsional changes could be reorienting the -10 and -35 elements to a favorable conformation for RNA polymerase occupancy at the mom promoter.
authors.affiliation: Microbiology and Cell Biology Department, Indian Institute of Science, Bangalore, 560 012, India.
authors.forename: S
authors.initials: S
authors.lastname: Basak
authors.forename: V
authors.initials: V
authors.lastname: Nagaraja
mesh_terms: D010583:Bacteriophage mu / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D018983:DNA Footprinting; D004265:DNA Helicases / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D008954:Models, Biological; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation; D014764:Viral Proteins
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C090591:C protein, Bacteriophage Mu; D017931:DNA Primers; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D015534:Trans-Activators; D014764:Viral Proteins; D012321:DNA-Directed RNA Polymerases; D004265:DNA Helicases