Dataset Information

Human MutL?, the MLH1-MLH3 heterodimer, is an endonuclease that promotes DNA expansion.

ABSTRACT: MutL proteins are ubiquitous and play important roles in DNA metabolism. MutL? (MLH1-MLH3 heterodimer) is a poorly understood member of the eukaryotic family of MutL proteins that has been implicated in triplet repeat expansion, but its action in this deleterious process has remained unknown. In humans, triplet repeat expansion is the molecular basis for ?40 neurological disorders. In addition to MutL?, triplet repeat expansion involves the mismatch recognition factor MutS? (MSH2-MSH3 heterodimer). We show here that human MutL? is an endonuclease that nicks DNA. Strikingly, incision of covalently closed, relaxed loop-containing DNA by human MutL? is promoted by MutS? and targeted to the strand opposite the loop. The resulting strand break licenses downstream events that lead to a DNA expansion event in human cell extracts. Our data imply that the mammalian MutL? is a unique endonuclease that can initiate triplet repeat DNA expansions.

SUBMITTER: Kadyrova LY

PROVIDER: S-EPMC7035508 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Publications

Human MutLγ, the MLH1-MLH3 heterodimer, is an endonuclease that promotes DNA expansion.

Kadyrova Lyudmila Y LY Gujar Vaibhavi V Burdett Vickers V Modrich Paul L PL Kadyrov Farid A FA

Proceedings of the National Academy of Sciences of the United States of America 20200203 7

MutL proteins are ubiquitous and play important roles in DNA metabolism. MutLγ (MLH1-MLH3 heterodimer) is a poorly understood member of the eukaryotic family of MutL proteins that has been implicated in triplet repeat expansion, but its action in this deleterious process has remained unknown. In humans, triplet repeat expansion is the molecular basis for ∼40 neurological disorders. In addition to MutLγ, triplet repeat expansion involves the mismatch recognition factor MutSβ (MSH2-MSH3 heterodime ...[more]

PMID: 32015124

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Project description:During meiotic prophase I, double-strand breaks (DSBs) initiate homologous recombination leading to non-crossovers (NCOs) and crossovers (COs). In mouse, 10% of DSBs are designated to become COs, primarily through a pathway dependent on the MLH1-MLH3 heterodimer (MutLγ). Mlh3 contains an endonuclease domain that is critical for resolving COs in yeast. We generated a mouse (Mlh3DN/DN) harboring a mutation within this conserved domain that is predicted to generate a protein that is catalytically inert. Mlh3DN/DN males, like fully null Mlh3-/- males, have no spermatozoa and are infertile, yet spermatocytes have grossly normal DSBs and synapsis events in early prophase I. Unlike Mlh3-/- males, mutation of the endonuclease domain within MLH3 permits normal loading and frequency of MutLγ in pachynema. However, key DSB repair factors (RAD51) and mediators of CO pathway choice (BLM helicase) persist into pachynema in Mlh3DN/DN males, indicating a temporal delay in repair events and revealing a mechanism by which alternative DSB repair pathways may be selected. While Mlh3DN/DN spermatocytes retain only 22% of wildtype chiasmata counts, this frequency is greater than observed in Mlh3-/- males (10%), suggesting that the allele may permit partial endonuclease activity, or that other pathways can generate COs from these MutLγ-defined repair intermediates in Mlh3DN/DN males. Double mutant mice homozygous for the Mlh3DN/DN and Mus81-/- mutations show losses in chiasmata close to those observed in Mlh3-/- males, indicating that the MUS81-EME1-regulated crossover pathway can only partially account for the increased residual chiasmata in Mlh3DN/DN spermatocytes. Our data demonstrate that mouse spermatocytes bearing the MLH1-MLH3DN/DN complex display the proper loading of factors essential for CO resolution (MutSγ, CDK2, HEI10, MutLγ). Despite these functions, mice bearing the Mlh3DN/DN allele show defects in the repair of meiotic recombination intermediates and a loss of most chiasmata.

Dataset Information

Human MutL?, the MLH1-MLH3 heterodimer, is an endonuclease that promotes DNA expansion.

Publications

Human MutLγ, the MLH1-MLH3 heterodimer, is an endonuclease that promotes DNA expansion.

Similar Datasets

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