Telomerase Is Essential to Alleviate pif1-induced Replication Stress at Telomeres

Genetics. 2009 Nov;183(3):779-91. doi: 10.1534/genetics.109.107631. Epub 2009 Aug 24.

Abstract

Pif1, an evolutionarily conserved helicase, negatively regulates telomere length by removing telomerase from chromosome ends. Pif1 has also been implicated in DNA replication processes such as Okazaki fragment maturation and replication fork pausing. We find that overexpression of Saccharomyces cervisiae PIF1 results in dose-dependent growth inhibition. Strong overexpression causes relocalization of the DNA damage response factors Rfa1 and Mre11 into nuclear foci and activation of the Rad53 DNA damage checkpoint kinase, indicating that the toxicity is caused by accumulation of DNA damage. We screened the complete set of approximately 4800 haploid gene deletion mutants and found that moderate overexpression of PIF1, which is only mildly toxic on its own, causes growth defects in strains with mutations in genes involved in DNA replication and the DNA damage response. Interestingly, we find that telomerase-deficient strains are also sensitive to PIF1 overexpression. Our data are consistent with a model whereby increased levels of Pif1 interfere with DNA replication, causing collapsed replication forks. At chromosome ends, collapsed forks result in truncated telomeres that must be rapidly elongated by telomerase to maintain viability.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Division
  • Checkpoint Kinase 2
  • DNA Breaks, Single-Stranded
  • DNA Damage
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • DNA Repair
  • DNA Replication / genetics*
  • Endodeoxyribonucleases / genetics
  • Endodeoxyribonucleases / metabolism
  • Exodeoxyribonucleases / genetics
  • Exodeoxyribonucleases / metabolism
  • Gene Expression Regulation, Fungal
  • Immunoblotting
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Microscopy, Fluorescence
  • Mutation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • Replication Protein A / genetics
  • Replication Protein A / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Telomerase / genetics
  • Telomerase / metabolism*
  • Telomere / genetics*

Substances

  • Cell Cycle Proteins
  • Luminescent Proteins
  • RFA1 protein, S cerevisiae
  • Replication Protein A
  • Saccharomyces cerevisiae Proteins
  • Checkpoint Kinase 2
  • Protein-Serine-Threonine Kinases
  • RAD53 protein, S cerevisiae
  • Telomerase
  • Endodeoxyribonucleases
  • Exodeoxyribonucleases
  • MRE11 protein, S cerevisiae
  • PIF1 protein, S cerevisiae
  • DNA Helicases