Cherlhyun Jeong1,8, Won-Ki Cho1,8, Kyung-Mi Song2, Christopher Cook3, Tae-Young Yoon4,5, Changill Ban2, Richard Fishel3,6 & Jong-Bong Lee1,7
1Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, Korea. 2Department of Chemistry, POSTECH, Pohang, Korea. 3Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Medical Center, Columbus, Ohio, USA. 4Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejon, Korea. 5Institute for the Biocentury, KAIST, Daejon, Korea. 6Physics Department, The Ohio State University, Columbus, Ohio, USA. 7School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang, Korea. 8These authors contributed equally to this work. Correspondence should be addressed to J.-B.L., C.B. or R.F.
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.