A putative curved DNA region upstream of rcsA in Escherichia coli plays a key role in transcriptional regulation by H-NS

It is well established that in Escherichia coli, the histone-like nucleoid structuring (H-NS) protein also functions as negative regulator of rcsA transcription. However, the exact mode of regulation of rcsA transcription by H-NS has not been studied extensively. Here, we report the multicopy effect of dominant-negative hns alleles on the transcription of rcsA based on expression of cps-lac transcriptional fusion in ∆lon, ∆lon rpoB12, ∆lon rpoB77 and lon⁺ strains. Our results indicate that H-NS defective in recognizing curved DNA fails to repress rcsA transcription significantly, while nonoligomeric H-NS molecules still retain the repressor activity to an appreciable extent. Together with bioinformatics analysis, our study envisages a critical role for the putative curved DNA region present upstream of rcsA promoter in the transcriptional regulation of rcsA by H-NS.