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Published on: November 10, 2016
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Dynamic human MutSα-MutLα complexes compact mismatched DNA
Kira C Bradford1,2, Hunter Wilkins1, Pengyu Hao3
1Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599.
Summary
Human DNA mismatch repair (MMR) proteins MutSα and MutLα form large, dynamic complexes on DNA to correct replication errors. These structures compact DNA, potentially enhancing repair efficiency and preventing interference.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- DNA mismatch repair (MMR) is crucial for genomic stability, correcting replication errors.
- Mutations in MMR proteins cause Lynch syndrome, a common hereditary cancer.
- Existing MMR models are largely based on prokaryotic systems and lack detail on human complex structures.
Purpose of the Study:
- To investigate the structure-function properties of human MutSα-MutLα complexes during DNA mismatch repair.
- To explore the time- and concentration-dependent assembly and conformations of these complexes on DNA.
Main Methods:
- Atomic force microscopy (AFM) was used to visualize DNA-protein complexes.
- Combined with other methods to analyze complex formation and dynamics.
Main Results:
- Human MutSα-MutLα complexes assemble into large, multimeric structures (3-8 proteins) around DNA mismatches.
- These complexes undergo conformational changes, folding and compacting the DNA within minutes.
- Observed assembly contrasts with models of diffusive MMR complexes.
Conclusions:
- MutSα actively localizes MutLα near mismatches, promoting DNA configurations for efficient repair.
- These complexes may protect the repair site from nucleosome interference and remodel nucleosomes.
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