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A CDK-Dependent Phosphorylation of a Novel Domain of Rif1 Regulates its Function during Telomere Damage and Other

Cameron M Robertson1, Yuan Xue1, Shobir Chowdhury1

  • 1Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK.

Molecular and Cellular Biology
|May 4, 2023
PubMed

Insights

Rif1 phosphorylation at serines 57 and 110 inhibits its accumulation on damaged chromosomes, impacting cell proliferation during telomere damage. Checkpoint kinases and Cdk1 activity regulate this crucial DNA damage response.

Area of Science:

  • Cellular biology
  • Molecular genetics
  • DNA repair mechanisms

Background:

  • Rif1 protein is a key regulator of telomere length, DNA replication, and DNA damage responses in budding yeast.
  • Previous studies identified Rif1 posttranslational modifications, but their role in DNA damage response, particularly telomere damage, remained unclear.

Purpose of the Study:

  • To investigate posttranslational modifications of Rif1 during telomere damage.
  • To identify specific sites and regulatory mechanisms of Rif1 phosphorylation in response to DNA damage.

Main Methods:

  • Utilized immunoblotting techniques.
  • Employed budding yeast models: cdc13-1 mutant and tlc1Δ deletion strains to induce telomere damage.
  • Investigated the role of specific serine residues (S57, S110) and the phospho-gate domain (PGD) of Rif1.

Main Results:

  • Discovered that Rif1 is phosphorylated during telomere damage, with serines 57 and 110 in the novel PGD being critical.
  • Observed that Rif1 phosphorylation inhibits its accumulation on damaged chromosomes and impairs cell proliferation under telomere damage conditions.
  • Identified checkpoint kinases as upstream regulators and Cdk1 activity as essential for maintaining Rif1 phosphorylation.
  • Demonstrated that S57 and S110 phosphorylation is also essential during genotoxic stress and mitotic stress.

Conclusions:

  • Rif1 phosphorylation, particularly at S57 and S110 within the PGD, plays a significant role in cellular responses to telomere damage, genotoxic agents, and mitotic stress.
  • This phosphorylation event appears to act as an inhibitory mechanism, limiting Rif1's function on damaged DNA and affecting cell survival.
  • Proposed a novel "Pliers" model to elucidate the function of PGD phosphorylation in various DNA damage contexts.
Keywords:
DNA damage checkpointsRif1budding yeastcyclin-dependent kinasestelomere

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