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The Holliday junction (HJ) is a central intermediate of homologous recombination. Its cleavage is critical for the formation of crossover recombinants during meiosis, which in turn helps to establish chiasmata and promote genetic diversity. Enzymes that cleave HJs, called HJ resolvases, have been identified in all domains of life except eukaryotic nuclei. Controversially, the Mus81-Eme1 endonuclease has been proposed to be an example of a eukaryotic nuclear resolvase. However, hitherto little or no HJ cleavage has been detected in recombinant preparations of Mus81-Eme1. Here, we report the purification of active forms of recombinant Schizosaccharomyces pombe Mus81-Eme1 and Saccharomyces cerevisiae Mus81-Mms4, which display robust HJ cleavage in vitro, which, in the case of Mus81-Eme1, is as good as the archetypal HJ resolvase RuvC in single turnover kinetic analysis. We also present genetic evidence that suggests that this activity might be utilised as a back-up to Mus81-Eme1's main activity of cleaving nicked HJs during meiosis in S. pombe.

Original publication




Journal article



Publication Date





1891 - 1901


Base Sequence, Crossing Over, Genetic, DNA, Cruciform, DNA-Binding Proteins, Endodeoxyribonucleases, Endonucleases, Escherichia coli Proteins, Flap Endonucleases, Magnesium, Meiosis, Models, Genetic, Molecular Sequence Data, Recombinant Proteins, Recombination, Genetic, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Schizosaccharomyces, Schizosaccharomyces pombe Proteins, Trans-Activators, Ultracentrifugation