The phasevarion: A genetic system controlling coordinated, random switching of expression of multiple genes

Yogitha N. Srikhanta, Tina L. Maguire, Katryn J. Stacey, Sean M. Grimmond, Michael P. Jennings

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151 Citations (Scopus)


Several host-adapted bacterial pathogens contain methyltransferases associated with type III restriction-modification (R-M) systems that are subject to reversible, high-frequency on/off switching of expression (phase variation). To investigate the role of phase-variable expression of R-M systems, we made a mutant strain lacking the methyltransferase (mod) associated with a type III R-M system of Haemophilus influenzas and analyzed its phenotype. By microarray analysis, we identified a number of genes that were either up- or down-regulated in the mod mutant strain. This system reports the coordinated random switching of a set of genes in a bacterial pathogen and may represent a widely used mechanism.

Original languageEnglish
Pages (from-to)5547-5551
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number15
Publication statusPublished - 12 Apr 2005
Externally publishedYes


  • DNA methyltransferase
  • Haemophilus influenzae
  • Phase variation

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