Tel1ATM and Rad3ATR kinases promote Ccq1-Est1 interaction to maintain telomeres in fission yeast

Nat Struct Mol Biol. 2011 Nov 20;18(12):1408-13. doi: 10.1038/nsmb.2187.

Abstract

The evolutionarily conserved shelterin complex has been shown to play both positive and negative roles in telomerase regulation in mammals and fission yeast. Although shelterin prevents the checkpoint kinases ATM and ATR from fully activating DNA damage responses at telomeres in mammalian cells, those kinases also promote telomere maintenance. In fission yeast, cells lacking both Tel1 (ATM ortholog) and Rad3 (ATR ortholog) fail to recruit telomerase to telomeres and survive by circularizing chromosomes. However, the critical telomere substrate(s) of Tel1(ATM) and Rad3(ATR) was unknown. Here we show that phosphorylation of the shelterin subunit Ccq1 on Thr93, redundantly mediated by Tel1(ATM) and/or Rad3(ATR), is essential for telomerase association with telomeres. In addition, we show that the telomerase subunit Est1 interacts directly with the phosphorylated Thr93 of Ccq1 to ensure telomere maintenance. The shelterin subunits Taz1, Rap1 and Poz1 (previously established inhibitors of telomerase) were also found to negatively regulate Ccq1 phosphorylation. These findings establish Tel1(ATM)/Rad3(ATR)-dependent Ccq1 Thr93 phosphorylation as a critical regulator of telomere maintenance in fission yeast.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Cycle Proteins / chemistry
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / physiology*
  • Checkpoint Kinase 2
  • Models, Genetic
  • Models, Molecular
  • Mutation
  • Phosphorylation
  • Protein Interaction Mapping
  • Protein Kinases / chemistry
  • Protein Kinases / metabolism
  • Protein Kinases / physiology*
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases / chemistry
  • Protein-Serine-Threonine Kinases / metabolism
  • Protein-Serine-Threonine Kinases / physiology*
  • Schizosaccharomyces / enzymology*
  • Schizosaccharomyces pombe Proteins / chemistry
  • Schizosaccharomyces pombe Proteins / metabolism*
  • Schizosaccharomyces pombe Proteins / physiology*
  • Telomerase / chemistry
  • Telomerase / metabolism*
  • Telomere / metabolism*

Substances

  • Ccq1 protein, S pombe
  • Cell Cycle Proteins
  • Schizosaccharomyces pombe Proteins
  • Protein Kinases
  • Checkpoint Kinase 2
  • Protein-Serine-Threonine Kinases
  • rad3 protein, S pombe
  • tel1 protein, S pombe
  • EST1 protein, S pombe
  • Telomerase