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H-NS binding on dicA promoter DNA inhibits dicA gene expression
Korean J. Microbiol 2019;55(3):191-198
Published online September 30, 2019
© 2019 The Microbiological Society of Korea.

Sang Hoon Yun1,2†, Yonho Lee1†, and Heon M. Lim1*

1Department of Biological Sciences, College of Biological Sciences and Biotechnology, Chungnam National University, Daejeon 34134, Republic of Korea
2Alteogen Inc., Daejeon 34054, Republic of Korea
Correspondence to: *E-mail: hmlim@cnu.ac.kr; Tel.: +82-42-821-6276; Fax: +82-42-822-9690
These authors contributed equally to this work.
Received July 5, 2019; Revised August 9, 2019; Accepted August 26, 2019.
Abstract
H-NS binds to promoter DNA and works as a general transcription silencer. DicA protein, by binding to the promoter DNA of dicA, activates dicA expression and at the same time inhibits expression of dicF and dicB, thus, exerting cell division control in Escherichia coli. H-NS complexed with a nucleoid protein Cnu was known to be involved in dicA expression. However, the exact nature of H-NS binding to dicA promoter DNA and the consequences of H-NS binding in expression of dicA is not clear. In this study, we explored the DNA binding activity of H-NS on the promoter DNA of dicA and found that H-NS binding occurs exclusively to the dicA promoter DNA. We never observed, however, H-NS binding at the vicinity of the dicA promoter. Temperature dependent oligomerization of H-NS was observed during DNA binding and the Cnu protein enhances the oligomerization process of H-NS binding. In vivo measurement of dicA expression in an hns deleted strain showed that dicA expression increased. These results demonstrated that H-NS binds specifically to dicA promoter DNA and functions as a transcription silencer.
Keywords : Escherichia coli, Cnu, dicA, filamentous growth, H-NS, temperature-dependent DNA binding


September 2019, 55 (3)