Dataset Information

Mispair-bound human MutS-MutL complex triggers DNA incisions and activates mismatch repair.

ABSTRACT: DNA mismatch repair (MMR) relies on MutS and MutL ATPases for mismatch recognition and strand-specific nuclease recruitment to remove mispaired bases in daughter strands. However, whether the MutS-MutL complex coordinates MMR by ATP-dependent sliding on DNA or protein-protein interactions between the mismatch and strand discrimination signal is ambiguous. Using functional MMR assays and systems preventing proteins from sliding, we show that sliding of human MutSα is required not for MMR initiation, but for final mismatch removal. MutSα recruits MutLα to form a mismatch-bound complex, which initiates MMR by nicking the daughter strand 5' to the mismatch. Exonuclease 1 (Exo1) is then recruited to the nick and conducts 5' → 3' excision. ATP-dependent MutSα dissociation from the mismatch is necessary for Exo1 to remove the mispaired base when the excision reaches the mismatch. Therefore, our study has resolved a long-standing puzzle, and provided new insights into the mechanism of MMR initiation and mispair removal.

SUBMITTER: Ortega J

PROVIDER: S-EPMC8089094 | biostudies-literature | 2021 May

REPOSITORIES: biostudies-literature

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Mispair-bound human MutS-MutL complex triggers DNA incisions and activates mismatch repair.

Ortega Janice J Lee Grace Sanghee GS Gu Liya L Yang Wei W Li Guo-Min GM

Cell research 20210128 5

DNA mismatch repair (MMR) relies on MutS and MutL ATPases for mismatch recognition and strand-specific nuclease recruitment to remove mispaired bases in daughter strands. However, whether the MutS-MutL complex coordinates MMR by ATP-dependent sliding on DNA or protein-protein interactions between the mismatch and strand discrimination signal is ambiguous. Using functional MMR assays and systems preventing proteins from sliding, we show that sliding of human MutSα is required not for MMR initiati ...[more]

PMID: 33510387

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Project description:BackgroundAcinetobacter baylyi ADP1 is an ideal bacterial strain for high-throughput genetic analysis as the bacterium is naturally transformable. Thus, ADP1 can be used to investigate DNA mismatch repair, a mechanism for repairing mismatched bases. We used the mutS deletion mutant (XH439) and mutL deletion mutant (XH440), and constructed a mutS mutL double deletion mutant (XH441) to investigate the role of the mismatch repair system in A. baylyi.ResultsWe determined the survival rates after UV irradiation and measured the mutation frequencies, rates and spectra of wild-type ADP1 and mutSL mutant via rifampin resistance assay (RifR assay) and experimental evolution. In addition, transformation efficiencies of genomic DNA in ADP1 and its three mutants were determined. Lastly, the relative growth rates of the wild type strain, three constructed deletion mutants, as well as the rifampin resistant mutants obtained from RifR assays, were measured. All three mutants had higher survival rates after UV irradiation than wild type, especially the double deletion mutant. Three mutants showed higher mutation frequencies than ADP1 and favored transition mutations in RifR assay. All three mutants showed increased mutation rates in the experimental evolution. However, only XH439 and XH441 had higher mutation rates than the wild type strain in RifR assay. XH441 showed higher transformation efficiency than XH438 when donor DNA harbored transition mutations. All three mutants showed higher growth rates than wild-type, and these four strains displayed higher growth rates than almost all their rpoB mutants. The growth rate results showed different amino acid mutations in rpoB resulted in different extents of reduction in the fitness of rifampin resistant mutants. However, the fitness cost brought by the same mutation did not vary with strain background.ConclusionsWe demonstrated that inactivation of both mutS and mutL increased the mutation rates and frequencies in A. baylyi, which would contribute to the evolution and acquirement of rifampicin resistance. The mutS deletion is also implicated in increased mutation rates and frequencies, suggesting that MutL may be activated even in the absence of mutS. The correlation between fitness cost and rifampin resistance mutations in A. baylyi is firstly established.

Dataset Information

Mispair-bound human MutS-MutL complex triggers DNA incisions and activates mismatch repair.

Publications

Mispair-bound human MutS-MutL complex triggers DNA incisions and activates mismatch repair.

Similar Datasets

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