title: Phase variable type III restriction-modification systems of host-adapted bacterial pathogens.
abstract: Phase variation, the high-frequency on/off switching of gene expression, is a common feature of host-adapted bacterial pathogens. Restriction-modification (R-M) systems, which are ubiquitous among bacteria, are classically assigned the role of cellular defence against invasion of foreign DNA. These enzymes are not obvious candidates for phase variable expression, a characteristic usually associated with surface-expressed molecules subject to host immune selection. Despite this, numerous type III R-M systems in bacterial pathogens contain repetitive DNA motifs that suggest the potential for phase variation. Several roles have been proposed for phase variable R-M systems based on DNA restriction function. However, there is now evidence in several important human pathogens, including Haemophilus influenzae, Neisseria meningitidis and Neisseria gonorrhoeae, that these systems are 'phasevarions' (phase variable regulons) controlling expression of multiple genes via a novel epigenetic mechanism.
authors: School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Qld 4072, Australia.
authors: Kate L
authors: KL
authors: Fox
authors: Yogitha N
authors: YN
authors: Srikhanta
authors: Michael P
authors: MP
authors: Jennings
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001419:Bacteria / Q000201:enzymology* / Q000235:genetics; D015280:DNA Restriction-Modification Enzymes / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006790:Host-Parasite Interactions; D006801:Humans
chemical_list: D015280:DNA Restriction-Modification Enzymes; D004269:DNA, Bacterial