The phasevarion: phase variation of type III DNA methyltransferases controls coordinated switching in multiple genes

Abstract

In several host-adapted pathogens, phase variation has been found to occur in genes that encode methyltransferases associated with type III restriction–modification systems. It was recently shown that in the human pathogens Haemophilus influenzae, Neisseria gonorrhoeae and Neisseria meningitidis phase variation of a type III DNA methyltransferase, encoded by members of the mod gene family, regulates the expression of multiple genes. This novel genetic system has been termed the 'phasevarion' (phase-variable regulon). The wide distribution of phase-variable mod family genes indicates that this may be a common strategy used by host-adapted bacterial pathogens to randomly switch between distinct cell types.