Abstract

Histone-like nucleoid structuring protein (H-NS) is a small but abundant protein present in enteric bacteria and is involved in compaction of the DNA and regulation of the transcription. Recent reports have suggested that H-NS binds to a specific AT rich DNA sequence than to intrinsically curved DNA in sequence independent manner. We detected two high-specificity H-NS binding sites in LEE5 promoter of EPEC centered at -110 and -138, which were close to the proposed consensus H-NS binding motif. To identify H-NS binding sequence in LEE5 promoter, we took a random mutagenesis approach and found the mutations at around -138 were specifically defective in the regulation byH-NS. It was concluded that H-NS exertsmaximumrepression via the specific sequence at around -138 and ubsequently contacts α subunit of RNAP through oligomerization.

• Keywords: LEE5; H-NS; nucleation site; consensus motif; transcriptional repression; gene regulation; transcription