the cnuk9e h-ns complex antagonizes dna binding of dica and leads to temperature-dependent filamentous growth in e. coli复杂的cnuk9e h-ns对抗dica dna结合,导致与温度有关的丝状大肠杆菌的增长.pdfVIP

The CnuK9E H-NS Complex Antagonizes DNA Binding of DicA and Leads to Temperature-Dependent Filamentous Growth in E. coli 1 1¤ 1 1 2 3 Sang Hoon Yun , Sang Chun Ji , Heung Jin Jeon , Xun Wang , Si Wouk Kim , Geunu Bak , 3 1 Younghoon Lee , Heon M. Lim * 1 Department of Biology, College of Biological Sciences and Biotechnology, Chungnam National University, Taejon, Republic of Korea, 2 Department of Environmental Engineering, Pioneer Research Center for Controlling of Harmful Algal Blooming, Chosun University, Gwangju, Republic of Korea, 3 Department of Chemistry, KAIST, Daejeon, Republic of Korea 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 37uC. 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 25uC 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 37uC, presumably due to the lower operator binding of DicA at 37uC. These data suggest that the temperature- dependent negative effect of CnuK9E on DicA binding plays a major role in filamentous