RT Journal Article SR Electronic(1) A1 Yang, Ji A1 Tauschek, Marija A1 Strugnell, Richard A1 Robins-Browne, Roy M.YR 2005 T1 The H-NS protein represses transcription of the eltAB operon, which encodes heat-labile enterotoxin in enterotoxigenic Escherichia coli, by binding to regions downstream of the promoter JF Microbiology, VO 151 IS 4 SP 1199 OP 1208 DO https://doi.org/10.1099/mic.0.27734-0 PB Microbiology Society, SN 1465-2080, AB Heat-labile enterotoxin, a major virulence determinant of enterotoxigenic Escherichia coli, is encoded by the eltAB operon. To elucidate the molecular mechanism by which the heat-stable nucleoid-structural (H-NS) protein controls transcription of eltAB, the authors constructed an eltAB–lacZ transcriptional fusion and performed β-galactosidase analysis. The results showed that H-NS protein exerts fivefold repression on transcription from the eltAB promoter at 37 °C and 10-fold repression at 22 °C. Two silencer regions that were required for H-NS-mediated repression of eltAB expression were identified, both of which were located downstream of the start site of transcription. One silencer was located between +31 and +110, the other between +460 and +556, relative to the start site of transcription, and they worked cooperatively in repression. DNA sequences containing the silencers were predicted to be curved by in silico analysis and bound H-NS protein directly in vitro. Repression of eltAB transcription by H-NS was independent of promoter strength, and the presence of H-NS protein did not affect promoter opening in vitro, indicating that repression was achieved by inhibiting promoter clearance or blocking transcription elongation, probably via DNA looping between the two silencers., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.27734-0