H-NS Can Facilitate Specific DNA-binding by RNA Polymerase in AT-rich Gene Regulatory Regions

Extremely at-rich dna sequences present a challenging template for specific recognition by rna polymerase. in bacteria,this is because the promoter -10 hexamer,the major dna element recognised by rna polymerase,is itself at-rich. we show that histone-like nucleoid structuring (h-ns) protein can facilitate correct recognition of a promoter by rna polymerase in at-rich gene regulatory regions. thus,at the escherichia coli ehxcabd operon,rna polymerase is unable to distinguish between the promoter -10 element and similar overlapping sequences. this problem is resolved in native nucleoprotein because the overlapping sequences are masked by h-ns. our work provides mechanistic insight into nucleoprotein structure and its effect on protein-dna interactions in prokaryotic cells. © 2013 singh and grainger.