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Available structures
PDB Ortholog search: PDBe RCSB
Aliases MUS81, SLX3, MUS81 structure-specific endonuclease subunit
External IDs MGI: 1918961 HomoloGene: 5725 GeneCards: MUS81
RNA expression pattern
PBB GE MUS81 218463 s at fs.png
More reference expression data
Species Human Mouse
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC) Chr 11: 65.86 – 65.87 Mb Chr 19: 5.48 – 5.49 Mb
PubMed search [1] [2]
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Crossover junction endonuclease MUS81 is an enzyme that in humans is encoded by the MUS81 gene.[3][4][5]

In mammalian somatic cells, MUS81 and another structure specific DNA endonuclease, XPF (ERCC4), play overlapping and essential roles in completion of homologous recombination.[6] The significant overlap in function between these enzymes is most likely related to processing joint molecules such as D-loops and nicked Holliday junctions.[6]


MUS81 is a component of a minor chromosomal crossover (CO) pathway in the meiosis of budding yeast, plants and vertebrates.[7] However, in the protozoan Tetrahymena thermophila, MUS81 appears to be part of an essential (if not the predominant) CO pathway.[7] The MUS81 pathway also appears to be the predominant CO pathway in the fission yeast Schizosaccharomyces pombe.[7]

A current model of meiotic recombination, initiated by a double-strand break or gap, followed by pairing with an homologous chromosome and strand invasion to initiate the recombinational repair process. Repair of the gap can lead to crossover (CO) or non-crossover (NCO) of the flanking regions. CO recombination is thought to occur by the Double Holliday Junction (DHJ) model, illustrated on the right, above. NCO recombinants are thought to occur primarily by the Synthesis Dependent Strand Annealing (SDSA) model, illustrated on the left, above. Most recombination events appear to be the SDSA type.

The relationship of the CO pathway to the overall process of meiotic recombination is illustrated in the accompanying diagram. Recombination during meiosis is often initiated by a DNA double-strand break (DSB). During recombination, sections of DNA at the 5' ends of the break are cut away in a process called resection. In the strand invasion step that follows, an overhanging 3' end of the broken DNA molecule "invades" the DNA of an homologous chromosome that is not broken forming a displacement loop (D-loop). After strand invasion, the further sequence of events may follow either of two main pathways, leading to a crossover (CO) or a non-crossover (NCO) recombinant (see Genetic recombination). The pathway leading to a CO involves a double Holliday junction (DHJ) intermediate. Holliday junctions need to be resolved for CO recombination to be completed.

MU81-MMS4, in the budding yeast Saccharomyces cerevisiae, is a DNA structure-selective endonuclease that cleaves joint DNA molecules formed during homologous recombination in meiosis and mitosis.[8] The MUS81-MMS4 endonuclease, although a minor resolvase for CO formation in S. cerevisiae, is crucial for limiting chromosome entanglements by suppressing multiple consecutive recombination events from initiating from the same DSB.[9]

Mus81 deficient mice have significant meiotic defects including the failure to repair a subset of DSBs.[10]


MUS81 has been shown to interact with CHEK2.[3]


  1. ^ "Human PubMed Reference:". 
  2. ^ "Mouse PubMed Reference:". 
  3. ^ a b Chen XB, Melchionna R, Denis CM, Gaillard PH, Blasina A, Van de Weyer I, Boddy MN, Russell P, Vialard J, McGowan CH (Nov 2001). "Human Mus81-associated endonuclease cleaves Holliday junctions in vitro". Molecular Cell. 8 (5): 1117–27. doi:10.1016/S1097-2765(01)00375-6. PMID 11741546. 
  4. ^ Constantinou A, Chen XB, McGowan CH, West SC (Oct 2002). "Holliday junction resolution in human cells: two junction endonucleases with distinct substrate specificities". The EMBO Journal. 21 (20): 5577–85. doi:10.1093/emboj/cdf554. PMC 129086Freely accessible. PMID 12374758. 
  5. ^ "Entrez Gene: MUS81 MUS81 endonuclease homolog (S. cerevisiae)". 
  6. ^ a b Kikuchi K, Narita T, Pham VT, Iijima J, Hirota K, Keka IS, Mohiuddin, Okawa K, Hori T, Fukagawa T, Essers J, Kanaar R, Whitby MC, Sugasawa K, Taniguchi Y, Kitagawa K, Takeda S (2013). "Structure-specific endonucleases xpf and mus81 play overlapping but essential roles in DNA repair by homologous recombination". Cancer Res. 73 (14): 4362–71. doi:10.1158/0008-5472.CAN-12-3154. PMC 3718858Freely accessible. PMID 23576554. 
  7. ^ a b c Lukaszewicz A, Howard-Till RA, Loidl J (2013). "Mus81 nuclease and Sgs1 helicase are essential for meiotic recombination in a protist lacking a synaptonemal complex". Nucleic Acids Res. 41 (20): 9296–309. doi:10.1093/nar/gkt703. PMC 3814389Freely accessible. PMID 23935123. 
  8. ^ Mukherjee S, Wright WD, Ehmsen KT, Heyer WD (2014). "The Mus81-Mms4 structure-selective endonuclease requires nicked DNA junctions to undergo conformational changes and bend its DNA substrates for cleavage". Nucleic Acids Res. 42 (10): 6511–22. doi:10.1093/nar/gku265. PMC 4041439Freely accessible. PMID 24744239. 
  9. ^ Oke A, Anderson CM, Yam P, Fung JC (2014). "Controlling meiotic recombinational repair - specifying the roles of ZMMs, Sgs1 and Mus81/Mms4 in crossover formation". PLoS Genet. 10 (10): e1004690. doi:10.1371/journal.pgen.1004690. PMC 4199502Freely accessible. PMID 25329811. 
  10. ^ Holloway JK, Booth J, Edelmann W, McGowan CH, Cohen PE (2008). "MUS81 generates a subset of MLH1-MLH3-independent crossovers in mammalian meiosis". PLoS Genet. 4 (9): e1000186. doi:10.1371/journal.pgen.1000186. PMC 2525838Freely accessible. PMID 18787696. 

Further reading[edit]