title: Identification and characterization of human MUS81-MMS4 structure-specific endonuclease.
abstract: Replication forks may stall when they reach a block on the DNA template such as DNA damage, and the recovery of such stalled replication forks plays a crucial role in the maintenance of genomic stability. Holliday junctions, which are X-shaped DNA structures, are formed at the stalled replication forks and can accumulate if they are not cleaved by structure-specific endonucleases. Recently, a novel nuclease involved in resolving Holliday junction-like structures, Mus81, has been reported in yeast and humans. MUS81 has sequence homology to another DNA nuclease, XPF, which, with its partner ERCC1, makes the 5' incision during nucleotide excision repair. MUS81 also has a binding partner named Mms4 in Saccharomyces cerevisiae and Eme1 in Schizosaccharomyces pombe, but no such partner was identified in human cells. Here, we report identification of the binding partner of human MUS81, which we designate hMMS4. Using immunoaffinity purification we show that hMUS81 or hMMS4 alone have no detectable nuclease activity, but that the hMUS81.hMMS4 complex is a structure-specific nuclease that is capable of resolving fork structures.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7260, USA.
authors.forename: Müge
authors.initials: M
authors.lastname: Oğrünç
authors.forename: Aziz
authors.initials: A
authors.lastname: Sancar
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D004720:Endonucleases / Q000378:metabolism*; D045585:Flap Endonucleases; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D004720:Endonucleases; D045585:Flap Endonucleases; C411624:MUS81 protein, S cerevisiae; C498772:MUS81 protein, human; C112337:MMS4 protein, S cerevisiae