title: Slx1-Slx4 are subunits of a structure-specific endonuclease that maintains ribosomal DNA in fission yeast.
abstract: In most eukaryotes, genes encoding ribosomal RNAs (rDNA) are clustered in long tandem head-to-tail repeats. Studies of Saccharomyces cerevisiae have indicated that rDNA copy number is maintained through recombination events associated with site-specific blockage of replication forks (RFs). Here, we describe two Schizosaccharomyces pombe proteins, homologs of S. cerevisiae Slx1 and Slx4, as subunits of a novel type of endonuclease that maintains rDNA copy number. The Slx1-Slx4-dependent endonuclease introduces single-strand cuts in duplex DNA on the 3' side of junctions with single-strand DNA. Deletion of Slx1 or Rqh1 RecQ-like DNA helicase provokes rDNA contraction, whereas simultaneous elimination of Slx1-Slx4 endonuclease and Rqh1 is lethal. Slx1 associates with chromatin at two foci characteristic of the two rDNA repeat loci in S. pombe. We propose a model in which the Slx1-Slx4 complex is involved in the control of the expansion and contraction of the rDNA loci by initiating recombination events at stalled RFs.
authors.affiliation: Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Coulon
authors.forename: Pierre-Henri L
authors.initials: PHL
authors.lastname: Gaillard
authors.forename: Charly
authors.initials: C
authors.lastname: Chahwan
authors.forename: William Hayes
authors.initials: WH
authors.lastname: McDonald
authors.forename: John R
authors.initials: JR
authors.lastname: Yates
authors.forename: Paul
authors.initials: P
authors.lastname: Russell
mesh_terms: D002843:Chromatin / Q000378:metabolism*; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D021122:Protein Subunits / Q000378:metabolism; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D002843:Chromatin; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D004720:Endonucleases