H-NS: A universal regulator for a dynamic genome

The effect of the bacterial heat-stable nucleoid-structuring (H-NS) protein on gene expression is overwhelmingly negative and extends throughout the genome, pointing to an almost universal role for this nucleoid-associated protein as a transcriptional repressor. Its ability to exert widespread effects on gene expression probably reflects the fact that it binds to curved DNA, which is commonly found at promoters. H-NS and related proteins can engage in both homologous and heterologous protein-protein interactions. Recent data show that the genes that encode H-NS-like proteins can be carried on mobile genetic elements. This raises the possibility that horizontal gene transfer expands the repertoire of protein-protein interactions that nucleoid-associated proteins can engage in, with potentially profound consequences for the global gene-expression profile of the cell.