title: Characterization of HscC (Hsc62), homologue of Hsp70 in Escherichia coli: over-expression of HscC modulates the activity of house keeping sigma factor sigma70.
abstract: BACKGROUND
  HscC, the third member of the Hsp70 family in Escherichia coli, shares 33% identity with the other two homologues, DnaK and HscA, and displays ATPase activity. Genetic and biochemical evidence indicates that the DnaK-DnaJ chaperone system interacts with sigma32 and is involved in the negative regulation of the heat shock response. Although HscC is a highly conserved protein in the Hsp70 family, its function is still unknown.
  
  
  RESULTS
  We observed that the over-expression of HscC caused severe growth inhibition. To explore this effect, we performed primer extension analysis and a beta-galactosidase assay and found that HscC reduced the sigma70-dependent promoter activity. An in vitro transcription assay revealed that HscC inhibited sigma70-dependent transcription. In addition, the co-purification analysis showed that sigma70 co-eluted with HscC.
  
  
  CONCLUSIONS
  These results indicate that HscC forms a complex with sigma70 and may function as its negative modulator.
authors.affiliation: Department of Cell Biology, NARA Institute of Science and Technology, Ikoma 630-0101, Japan.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Arifuzzaman
authors.forename: Taku
authors.initials: T
authors.lastname: Oshima
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Nakade
authors.forename: Hirotada
authors.initials: H
authors.lastname: Mori
mesh_terms: D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D012808:Sigma Factor; C114584:hscC protein, E coli; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases; C063842:dnaK protein, E coli