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MutS switches between two fundamentally distinct clamps during mismatch repair

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Single-molecule trajectory analysis has suggested DNA repair proteins may carry out a one-dimensional (1D) search on naked DNA encompassing >10,000 nucleotides. Organized cellular DNA (chromatin) presents substantial barriers to such lengthy searches. Using dynamic single-molecule fluorescence resonance energy transfer, we determined that the mismatch repair (MMR) initiation protein MutS forms a transient clamp that scans duplex DNA for mismatched nucleotides by 1D diffusion for 1 s (~700 base pairs) while in continuous rotational contact with the DNA. Mismatch identification provokes ATP binding (3 s) that induces distinctly different MutS sliding clamps with unusual stability on DNA (~600 s), which may be released by adjacent single-stranded DNA (ssDNA). These observations suggest that ATP transforms short-lived MutS lesion scanning clamps into highly stable MMR signaling clamps that are capable of competing with chromatin and recruiting MMR machinery, yet are recycled by ssDNA excision tracts.

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Figure 1: Single-molecule FRET of Taq MutS on duplex DNA.
Figure 2: Taq MutS scans duplex DNA by rotational diffusion.
Figure 3: Single-molecule FRET of Taq MutS binding to a +dT mismatch.
Figure 4: ATP induces a long-lived FRET state of MutS.
Figure 5: Single-stranded DNA provokes the release of ATP-bound MutS sliding clamps.
Figure 6: Role of distinct MutS clamps in molecular switch model for MMR.

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  • 13 February 2011

    In the version of this article initially published online, the x axis for the right-hand graph in Figure 5c and the x axis for the graph in Figure 5d should have read 'Dwell time (s)'. The error has been corrected in all versions of this article.


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We thank J.-H. Park for helping with the FRET experiments. This work was supported by National Research Foundation of Korea grants funded by the Korean government (MEST) (no. 2008-0061211, no. 2009-351-C00118; C.J. postdoctoral fellowship), the Brain Korea 21 project, a POSTECH Basic Science Research Institute Grant (J.-B.L.), HRF-2008-314-C00218 (C.B.) and US National Institutes of Health grant CA067007 (R.F.).

Author information




C.J., R.F. and J.-B.L. designed the experiments. C.B. and K.-M.S. contributed essential reagents. C.J. and W.-K.C. carried out single-molecule analysis. C.C. carried out bulk analysis. C.J., W.-K.C., T.-Y.Y., C.B., R.F. and J.-B.L. analyzed the data. C.J., J.-B.L. and R.F. wrote the manuscript.

Corresponding authors

Correspondence to Changill Ban or Richard Fishel or Jong-Bong Lee.

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The authors declare no competing financial interests.

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Jeong, C., Cho, WK., Song, KM. et al. MutS switches between two fundamentally distinct clamps during mismatch repair. Nat Struct Mol Biol 18, 379–385 (2011).

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