Slx4 becomes phosphorylated after DNA damage in a Mec1/Tel1-dependent manner and is required for repair of DNA alkylation damage

Biochem J. 2005 Oct 15;391(Pt 2):325-33. doi: 10.1042/BJ20050768.


Members of the RecQ family of DNA helicases, mutated in several syndromes associated with cancer predisposition, are key regulators of genome stability. The Saccharomyces cerevisiae SLX4 gene is required for cell viability in the absence of Sgs1, the only yeast RecQ helicase. SLX4 encodes one subunit of the heterodimeric Slx1-Slx4 endonuclease, although its cellular function is not clear. Slx1-Slx4 was reported to preferentially cleave replication fork-like structures in vitro, and cells lacking SLX4 are hypersensitive to DNA alkylation damage. Here we report that Slx4 becomes phosphorylated in cells exposed to a wide range of genotoxins. Even though it has been proposed that the role of Slx4 is restricted to S-phase, Slx4 phosphorylation is observed in cells arrested in G1 or G2 phases of the cell cycle, but not during an unperturbed cell cycle. Slx4 phosphorylation is completely abolished in cells lacking the Mec1 and Tel1 protein kinases, critical regulators of genome stability, but is barely affected in the absence of both Rad53 and Chk1 kinases. Finally we show that, whereas both Slx1 and Slx4 are dispensable for activation of cell-cycle checkpoints, Slx4, but not Slx1, is required for repair of DNA alkylation damage in both aynchronously growing cells and in G2-phase-arrested cells. These results reveal Slx4 as a new target of the Mec1/Tel1 kinases, with a crucial role in DNA repair that is not restricted to the processing of stalled replisomes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkylation
  • Cell Cycle Proteins / genetics
  • Cell Division / genetics
  • Checkpoint Kinase 1
  • Checkpoint Kinase 2
  • DNA Damage*
  • DNA Repair*
  • DNA, Fungal / metabolism*
  • Endodeoxyribonucleases / genetics
  • Endodeoxyribonucleases / metabolism*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Deletion
  • Gene Expression Regulation, Fungal
  • Intracellular Signaling Peptides and Proteins
  • Mutagens / pharmacology
  • Phosphorylation
  • Protein Kinases / genetics
  • Protein-Serine-Threonine Kinases / genetics
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Signal Transduction


  • Cell Cycle Proteins
  • DNA, Fungal
  • Fungal Proteins
  • Intracellular Signaling Peptides and Proteins
  • Mutagens
  • Saccharomyces cerevisiae Proteins
  • Protein Kinases
  • Checkpoint Kinase 2
  • Checkpoint Kinase 1
  • MEC1 protein, S cerevisiae
  • Protein-Serine-Threonine Kinases
  • TEL1 protein, S cerevisiae
  • RAD53 protein, S cerevisiae
  • Endodeoxyribonucleases
  • SLX1 protein, S cerevisiae
  • SLX4 protein, S cerevisiae