%0 Journal Article
%T The CnuK9E H-NS Complex Antagonizes DNA Binding of DicA and Leads to Temperature-Dependent Filamentous Growth in E. coli
%A Sang Hoon Yun
%A Sang Chun Ji
%A Heung Jin Jeon
%A Xun Wang
%A Si Wouk Kim
%A Geunu Bak
%A Younghoon Lee
%A Heon M. Lim
%J PLOS ONE
%D 2012
%I Public Library of Science (PLoS)
%R 10.1371/journal.pone.0045236
%X 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 37ˇăC. 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 25ˇăC 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 37ˇăC, presumably due to the lower operator binding of DicA at 37ˇăC. 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 25ˇăC.
%U http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0045236