title: A LexA-related protein regulates redox-sensitive expression of the cyanobacterial RNA helicase, crhR.
abstract: Expression of the cyanobacterial DEAD-box RNA helicase, crhR, is regulated in response to conditions, which elicit reduction of the photosynthetic electron transport chain. A combination of electrophoretic mobility shift assay (EMSA), DNA affinity chromatography and mass spectrometry identified that a LexA-related protein binds specifically to the crhR gene. Transcript analysis indicates that lexA and crhR are divergently expressed, with lexA and crhR transcripts accumulating differentially under conditions, which respectively oxidize and reduce the electron transport chain. In addition, expression of the Synechocystis lexA gene is not DNA damage inducible and its amino acid sequence lacks two of three residues required for activity of prototypical LexA proteins, which repress expression of DNA repair genes in a range of prokaryotes. A direct effect of recombinant LexA protein on crhR expression was confirmed from the observation that LexA reduces crhR expression in a linear manner in an in vitro transcription/translation assay. The results indicate that the Synechocystis LexA-related protein functions as a regulator of redox-responsive crhR gene expression, and not DNA damage repair genes.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Patterson-Fortin
authors.forename: Kimberley R
authors.initials: KR
authors.lastname: Colvin
authors.forename: George W
authors.initials: GW
authors.lastname: Owttrim
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D001665:Binding Sites; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010084:Oxidation-Reduction; D011401:Promoter Regions, Genetic; D020365:RNA Helicases / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D011938:Rec A Recombinases / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D046939:Synechocystis / Q000201:enzymology / Q000235:genetics*; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D020365:RNA Helicases; D012333:RNA, Messenger; D011938:Rec A Recombinases; D012097:Repressor Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein