H-NS, Global Regulator of Gene Expression and Organizer of the Bacterial Nucleoid
Charles J. Dorman
from: Bacterial Regulatory Networks (Edited by: Alain A.M. Filloux). Caister Academic Press, U.K. (2012)
H-NS is an abundant DNA binding protein that has been found to influence the expression of hundreds of genes in those Gram-negative bacteria, chiefly Escherichia coli and Salmonella enterica, where its regulatory effects have been investigated. It also has the potential to organize the structure of the nucleoid. H-NS has a preference for binding to A+T-rich DNA and this preference underlies its targeting of genes that have been acquired by horizontal transfer. H-NS usually acts as a transcriptional silencer by binding to a nucleation site followed by lateral spreading with or without the creation of DNA-protein-DNA bridges; it may also act as an architectural component in the nucleoid. Bacteria use a multitude of mechanisms to displace H-NS or to attenuate its negative influence on gene expression. A paralogue of H-NS, called StpA, is an efficient RNA chaperone and controls a regulon of genes in S. enterica by influencing expression of the RpoS sigma factor. Orthologues of H-NS have been discovered on large self-transmissible plasmids, introducing a new dimension in considerations of the roles of H-NS-like proteins in horizontal gene transfer. Importantly, analogues of H-NS are now being discovered and characterized in Gram-negative bacteria such as Pseudomonas that are only distantly related to E. coli, in the medically important actinomycete Mycobacterium tuberculosis and even in Gram-positive organisms such as Bacillus subtilis read more ...