title: The CnuK9E H-NS complex antagonizes DNA binding of DicA and leads to temperature-dependent filamentous growth in E. coli.
abstract: Cnu (an OriC-binding nucleoid protein) associates with H-NS. A variant of Cnu was identified as a key factor for filamentous growth of a wild-type Escherichia coli strain at 37°C. This variant (CnuK9E) bears a substitution of a lysine to glutamic acid, causing a charge reversal in the first helix. The temperature-dependent filamentous growth of E. coli bearing CnuK9E could be reversed by either lowering the temperature to 25°C or lowering the CnuK9E concentration in the cell. Gene expression analysis suggested that downregulation of dicA by CnuK9E causes a burst of dicB transcription, which, in turn, elicits filamentous growth. In vivo assays indicated that DicA transcriptionally activates its own gene, by binding to its operator in a temperature-dependent manner. The antagonizing effect of CnuK9E with H-NS on DNA-binding activity of DicA was stronger at 37°C, presumably due to the lower operator binding of DicA at 37°C. These data suggest that the temperature-dependent negative effect of CnuK9E on DicA binding plays a major role in filamentous growth. The C-terminus of DicA shows significant amino acid sequence similarity to the DNA-binding domains of RovA and SlyA, regulators of pathogenic genes in Yersinia and Salmonella, respectively, which also show better DNA-binding activity at 25°C.
authors.affiliation: Department of Biology, College of Biological Sciences and Biotechnology, Chungnam National University, Taejon, Republic of Korea.
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Yun
authors.forename: Sang Chun
authors.initials: SC
authors.lastname: Ji
authors.forename: Heung Jin
authors.initials: HJ
authors.lastname: Jeon
authors.forename: Xun
authors.initials: X
authors.lastname: Wang
authors.forename: Si Wouk
authors.initials: SW
authors.lastname: Kim
authors.forename: Geunu
authors.initials: G
authors.lastname: Bak
authors.forename: Younghoon
authors.initials: Y
authors.lastname: Lee
authors.forename: Heon M
authors.initials: HM
authors.lastname: Lim
mesh_terms: D019943:Amino Acid Substitution; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D036781:Fimbriae Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: C505237:Cnu protein, E coli; D004268:DNA-Binding Proteins; C578516:DicA protein, E coli; D029968:Escherichia coli Proteins; C529458:FimG protein, E coli; D012097:Repressor Proteins; D036781:Fimbriae Proteins