Slx1-Slx4 are subunits of a structure-specific endonuclease that maintains ribosomal DNA in fission yeast.

Coulon S, Gaillard PHL, Chahwan C, McDonald WH, Yates JR, Russell P
Mol Biol Cell. 2004 15 (1): 71-80

PMID: 14528010 · PMCID: PMC307528 · DOI:10.1091/mbc.e03-08-0586

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.

MeSH Terms (14)

Chromatin DNA, Ribosomal DNA-Binding Proteins Endonucleases Microscopy, Fluorescence Models, Molecular Molecular Sequence Data Protein Subunits Recombination, Genetic Saccharomyces cerevisiae Saccharomyces cerevisiae Proteins Schizosaccharomyces Schizosaccharomyces pombe Proteins Sequence Alignment

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