Figure 4.
The effects of DNA methylation on Pap phase variation. Wild-type and mutant pap DNA regulatory regions are shown at the left. Substitutions in Lrp binding sites 3 and 4 are depicted by an “X” and point mutations in GATCdist and GATCprox that disrupt DNA methylation are shown as “GCTC” sequences. The Pap switch phenotypes under variation levels of Dam are shown at the right. “Switching” indicates reversible phase variation, “OFF” indicates locked OFF, “ON” indicates locked ON, and “ON” with an arrow indicates up-regulation of pap pilin transcription. At the upper right, “W.T.” indicates wild-type levels of Dam, “Dam−” indicates a deletion of the dam gene, and “Dam+++” indicates overproduction of Dam (>4-fold). Data are from refs. 8 and 10.