Methylation Patterns in Pap Regulatory DNA Control Pyelonephritis-Associated Pili Phase Variation in E. Coli

Cell. 1994 Feb 11;76(3):577-88. doi: 10.1016/0092-8674(94)90120-1.


We have examined the roles of pap DNA methylation patterns in the regulation of the switch between phase ON and OFF pyelonephritis-associated pili (Pap) expression states in E. coli. Two Dam methyltransferase sites, GATC1028 and GATC1130, were shown previously to be differentially methylated in phase ON versus phase OFF cells. In work presented here, these sites were mutated so that they could not be methylated, and the effects of these mutations on Pap phase variation were examined. Our results show that methylation of GATC1028 blocks formation of the ON state by inhibiting the binding of Lrp and PapI regulatory proteins to this site. Conversely, methylation of GATC1130 is required for the ON state. Evidence indicates that this occurs by the inhibition of binding of Lrp to sites overlapping the pilin promoter. A model describing how the transition between the phase ON and OFF methylation states might occur is presented.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Binding Sites
  • DNA, Bacterial / analysis
  • DNA, Bacterial / metabolism*
  • DNA-Binding Proteins / metabolism
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins
  • Fimbriae, Bacterial / physiology
  • Genes, Bacterial
  • Genetic Variation
  • Leucine-Responsive Regulatory Protein
  • Methylation
  • Methyltransferases / metabolism
  • Molecular Sequence Data
  • Mutagenesis
  • Promoter Regions, Genetic
  • Regulatory Sequences, Nucleic Acid*
  • Site-Specific DNA-Methyltransferase (Adenine-Specific)*
  • Substrate Specificity
  • Transcription Factors*


  • Bacterial Proteins
  • DNA, Bacterial
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Lrp protein, E coli
  • Transcription Factors
  • Leucine-Responsive Regulatory Protein
  • Methyltransferases
  • Dam methyltransferase
  • Site-Specific DNA-Methyltransferase (Adenine-Specific)
  • dam protein, E coli