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Updated: Jul 15, 2025

Author Spotlight: Unveiling the Role of SNF2L in Replication Fork Stability and Genome Duplication
05:55

Author Spotlight: Unveiling the Role of SNF2L in Replication Fork Stability and Genome Duplication

Published on: August 23, 2024

550

Telomeric DNA breaks in human induced pluripotent stem cells trigger ATR-mediated arrest and telomerase-independent

Katrina N Estep1,2, John W Tobias3, Rafael J Fernandez1

  • 1Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.

Journal of Molecular Cell Biology
|September 29, 2023
PubMed

Insights

Human stem cells use homologous recombination (HR) to repair telomere DNA breaks, independent of telomerase. This process maintains telomere length and cell survival, revealing a distinct stem cell response to DNA damage.

Area of Science:

  • Stem cell biology
  • DNA repair mechanisms
  • Telomere biology

Background:

  • Mechanisms of telomere protection are understood in differentiated cells, but poorly characterized in stem cells.
  • How stem cells sense and respond to telomere dysfunction, specifically telomeric double-strand breaks (DSBs), remains unclear.

Purpose of the Study:

  • To investigate DNA damage signaling, cell cycle, and transcriptome changes in human induced pluripotent stem cells (iPSCs) after inducing telomere-internal DSBs.
  • To elucidate the roles of telomerase and homologous recombination (HR) in iPSC response to telomeric DSBs.

Main Methods:

  • Engineered human iPSCs with an inducible TRF1-FokI fusion protein to create acute DSBs at telomeres.
  • Utilized CRISPR-Cas9 to inactivate telomerase reverse transcriptase.
  • Analyzed DNA damage response, cell cycle arrest, and telomere repair pathways.

Main Results:

  • Induced telomeric DSBs activated an ATR-dependent DNA damage response, causing p53-independent G2 cell cycle arrest.
  • Telomerase was dispensable for survival and repair of TRF1-FokI-induced telomeric breaks.
  • Homologous recombination (HR) effectively repaired telomeric DSBs, maintaining normal telomere length and cell survival.
  • Unlike mouse embryonic stem cells, HR in iPSCs maintained telomere length without extension.

Conclusions:

  • Homologous recombination plays a significant role in telomere maintenance in telomerase-positive iPSCs.
  • iPSCs exhibit unique responses to targeted telomeric DNA damage compared to other stem cells.
  • The findings highlight a novel mechanism for telomere maintenance in human pluripotent stem cells.
Keywords:
DNA damagealternative lengthening of telomeresdouble-strand breakspluripotent stem cellstelomerasetelomeres

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