Selective silencing of foreign DNA with low GC content by the H-NS protein in Salmonella.
Horizontal gene transfer plays a major role in microbial evolution. However, newly acquired sequences can decrease fitness unless integrated into preexisting regulatory networks. We found that the histone-like nucleoid structuring protein (H-NS) selectively silences horizontally acquired genes by targeting sequences with GC content lower than the resident genome. Mutations in hns are lethal in Salmonella unless accompanied by compensatory mutations in other regulatory loci. Thus, H-NS provides a previously unrecognized mechanism of bacterial defense against foreign DNA, enabling the acquisition of DNA from exogenous sources while avoiding detrimental consequences from unregulated expression of newly acquired genes. Characteristic GC/AT ratios of bacterial genomes may facilitate discrimination between a cell's own DNA and foreign DNA.
Navarre
William Wiley
WW
Department of Laboratory Medicine, University of Washington, Seattle, WA 98195, USA.
Porwollik
Steffen
S
Wang
Yipeng
Y
McClelland
Michael
M
Rosen
Henry
H
Libby
Stephen J
SJ
Fang
Ferric C
FC
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001482:Base Composition; D001665:Binding Sites; D047369:Chromatin Immunoprecipitation; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D020868:Gene Silencing; D022761:Gene Transfer, Horizontal; D016680:Genome, Bacterial; D016480:Helicobacter pylori / Q000235:genetics; D008957:Models, Genetic; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000235:genetics* / Q000502:physiology
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D012097:Repressor Proteins