Atomic force microscopy captures MutS tetramers initiating DNA mismatch repair.

In spite of extensive research, the mechanism by which MutS initiates DNA mismatch repair (MMR) remains controversial. We use atomic force microscopy (AFM) to capture how MutS orchestrates the first step of E. coli MMR. AFM images captured two types of MutS/DNA complexes: single-site binding and loop binding. In most of the DNA loops imaged, two closely associated MutS dimers formed a tetrameric complex in which one of the MutS dimers was located at or near the mismatch. Surprisingly, in the presence of ATP, one MutS dimer remained at or near the mismatch site and the other, while maintaining contact with the first dimer, relocated on the DNA by reeling in DNA, thereby producing expanding DNA loops. Our results indicate that MutS tetramers composed of two non-equivalent MutS dimers drive E. coli MMR, and these new observations now reconcile the apparent contradictions of previous 'sliding' and 'bending/looping' models of interaction between mismatch and strand signal.

Full Text

Duke Authors

Cited Authors

  • Jiang, Y; Marszalek, PE

Published Date

  • July 20, 2011

Published In

Volume / Issue

  • 30 / 14

Start / End Page

  • 2881 - 2893

PubMed ID

  • 21666597

Electronic International Standard Serial Number (EISSN)

  • 1460-2075

Digital Object Identifier (DOI)

  • 10.1038/emboj.2011.180

Language

  • eng

Citation Source

  • PubMed