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The Saccaromyces cerevisiae Mlh1-Mlh3 heterodimer is an endonuclease that preferentially binds to Holliday junctions


Ranjha, Lepakshi; Anand, Roopesh; Cejka, Petr (2014). The Saccaromyces cerevisiae Mlh1-Mlh3 heterodimer is an endonuclease that preferentially binds to Holliday junctions. Journal of Biological Chemistry, 289(9):5674-5686.

Abstract

MutLγ, a heterodimer of the MutL homologues Mlh1 and Mlh3, plays a critical role during meiotic homologous recombination. The meiotic function of Mlh3 is fully dependent on the integrity of a putative nuclease motif DQHA(X)2E(X)4E, inferring that the anticipated nuclease activity of Mlh1-Mlh3 is involved in the processing of joint molecules to generate crossover recombination products. Although a vast body of genetic and cell biological data regarding Mlh1-Mlh3 is available, mechanistic insights into its function have been lacking due to the unavailability of the recombinant protein complex. Here we expressed the yeast Mlh1-Mlh3 heterodimer and purified it into near homogeneity. We show that recombinant MutLγ is a nuclease that nicks double-stranded DNA. We demonstrate that MutLγ binds DNA with a high affinity, and shows a marked preference for Holliday junctions. We also expressed the human MLH1-MLH3 complex and show that preferential binding to Holliday junctions is a conserved capacity of eukaryotic MutLγ complexes. Specific DNA recognition has never been observed with any other eukaryotic MutL homologue. MutLγ thus represents a new paradigm for the function of the eukaryotic MutL protein family. We provide insights into the mode of Holliday junction recognition, and show that Mlh1-Mlh3 prefers to bind the open unstacked Holliday junction form. This further supports the model where MutLγ is part of a complex acting on joint molecules to generate crossovers in meiosis.

Abstract

MutLγ, a heterodimer of the MutL homologues Mlh1 and Mlh3, plays a critical role during meiotic homologous recombination. The meiotic function of Mlh3 is fully dependent on the integrity of a putative nuclease motif DQHA(X)2E(X)4E, inferring that the anticipated nuclease activity of Mlh1-Mlh3 is involved in the processing of joint molecules to generate crossover recombination products. Although a vast body of genetic and cell biological data regarding Mlh1-Mlh3 is available, mechanistic insights into its function have been lacking due to the unavailability of the recombinant protein complex. Here we expressed the yeast Mlh1-Mlh3 heterodimer and purified it into near homogeneity. We show that recombinant MutLγ is a nuclease that nicks double-stranded DNA. We demonstrate that MutLγ binds DNA with a high affinity, and shows a marked preference for Holliday junctions. We also expressed the human MLH1-MLH3 complex and show that preferential binding to Holliday junctions is a conserved capacity of eukaryotic MutLγ complexes. Specific DNA recognition has never been observed with any other eukaryotic MutL homologue. MutLγ thus represents a new paradigm for the function of the eukaryotic MutL protein family. We provide insights into the mode of Holliday junction recognition, and show that Mlh1-Mlh3 prefers to bind the open unstacked Holliday junction form. This further supports the model where MutLγ is part of a complex acting on joint molecules to generate crossovers in meiosis.

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Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Molecular Cancer Research
07 Faculty of Science > Institute of Molecular Cancer Research
Dewey Decimal Classification:570 Life sciences; biology
Language:English
Date:2014
Deposited On:04 Mar 2014 10:05
Last Modified:08 Dec 2017 02:59
Publisher:American Society for Biochemistry and Molecular Biology
ISSN:0021-9258
Additional Information:This research was originally published in Journal of Biological Chemistry. Lepakshi Ranjha, Roopesh Anand, and Petr Cejka: The Saccharomyces cerevisiae Mlh1-Mlh3 heterodimer is an endonuclease that preferentially binds to Holliday junctions. Journal of Biological Chemistry (2014); 289(9): 5674-5686. © the American Society for Biochemistry and Molecular Biology.
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:https://doi.org/10.1074/jbc.M113.533810
PubMed ID:24443562

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