Protein roadblocks and helix discontinuities are barriers to the initiation of mismatch repair.

Journal Article (Journal Article)

The hemimethylated d(GATC) sequence that directs Escherichia coli mismatch repair can reside on either side of a mismatch at a separation distance of 1,000 bp or more. Initiation of repair involves the mismatch-, MutS-, and MutL-dependent activation of MutH endonuclease, which incises the unmethylated strand at the d(GATC) sequence, with the ensuing strand break serving as the loading site for the appropriate 3'-to-5' or 5'-to-3' excision system. However, the mechanism responsible for the coordinated recognition of the mismatch and a hemimodified d(GATC) site is uncertain. We show that a protein roadblock (EcoRI(E111Q), a hydrolytically defective form of EcoRI endonuclease) placed on the helix between the two DNA sites inhibits MutH activation by 70-80% and that events that escape inhibition are attributable, at least in part, to diffusion of EcoRI(E111Q) away from its recognition site. We also demonstrate that a double-strand break located within the shorter path linking the mismatch and a d(GATC) site in a circular heteroduplex abolishes MutH activation, whereas a double-strand break within the longer path is without effect. These findings support the idea that initiation of mismatch repair involves signaling along the helix contour.

Full Text

Duke Authors

Cited Authors

  • Pluciennik, A; Modrich, P

Published Date

  • July 31, 2007

Published In

Volume / Issue

  • 104 / 31

Start / End Page

  • 12709 - 12713

PubMed ID

  • 17620611

Pubmed Central ID

  • PMC1913546

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.0705129104


  • eng

Conference Location

  • United States