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Author Spotlight: Advanced Single-Molecule Techniques for Investigating Telomeric Protein-DNA Interactions
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A sharp Pif1-dependent threshold separates DNA double-strand breaks from critically short telomeres

Jonathan Strecker1,2, Sonia Stinus3, Mariana Pliego Caballero3

  • 1Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.

Elife
|August 23, 2017
PubMed

Insights

DNA double-strand breaks (DSBs) and short telomeres have different fates. A minimum of 34 base pairs of telomeric repeats signal DNA ends to avoid Pif1 helicase, allowing telomerase extension and distinguishing telomeres from DSBs.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cell Biology

Background:

  • DNA double-strand breaks (DSBs) and short telomeres share structural similarities but have distinct cellular outcomes.
  • Cells must differentiate between DSBs requiring repair and telomeres needing telomerase extension.

Purpose of the Study:

  • To investigate the critical length threshold that distinguishes telomeres from DSBs in Saccharomyces cerevisiae.
  • To understand the role of Pif1 helicase and Cdc13 in regulating telomere length and end fate.

Main Methods:

  • Utilizing Pif1 helicase as a sensor for DNA end recognition.
  • Experimentally manipulating telomeric repeat lengths (TG1-3)n to determine Pif1 insensitivity.
  • Analyzing telomerase extension efficiency at different telomere lengths.

Main Results:

  • A transition point of 34 base pairs (bp) of telomeric repeats was identified, rendering DNA ends insensitive to Pif1 helicase.
  • Telomeres shorter than approximately 40 bp showed inefficient telomerase extension.
  • Cdc13 protein is proposed to confer Pif1 insensitivity to telomeric ends with at least 34 bp.

Conclusions:

  • The Pif1 activity threshold, defined by ~34 bp of telomeric repeats, acts as a critical determinant between DSBs and functional telomeres.
  • This length-dependent mechanism ensures proper telomere maintenance and prevents aberrant processing of chromosome ends.
Keywords:
DNA double-stand breaksGenome stabilityS. cerevisiaeTelomereschromosomesgenes

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