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An ATR-PrimPol pathway confers tolerance to oncogenic KRAS-induced and heterochromatin-associated replication stress

Taichi Igarashi1,2, Marianne Mazevet1, Takaaki Yasuhara3

  • 1Laboratory of Genome Stress Signaling, National Cancer Center Research Institute, Chuo-ku, Tokyo, 104-0045, Japan.

Nature Communications
|August 17, 2023
PubMed

Insights

Activating KRAS oncogenes cause replication stress via chromatin compaction, but ATR and PrimPol help cancer cells survive. This survival mechanism, however, leads to genomic instability.

Area of Science:

  • Molecular Biology
  • Cancer Biology
  • Genetics

Background:

  • Activation of the KRAS oncogene is a known source of replication stress in cancer cells.
  • The mechanisms by which KRAS induces replication stress and how cancer cells tolerate it are not fully understood.

Purpose of the Study:

  • To investigate how KRAS oncogene activation generates replication stress.
  • To elucidate the mechanisms of replication stress tolerance in KRAS-driven cancers.
  • To identify key molecular players involved in KRAS-induced replication stress response.

Main Methods:

  • Induction of KRASG12V expression in untransformed cells.
  • Chromatin immunoprecipitation assays to assess chromatin compaction (H3K27me3, HP1).
  • Analysis of replication fork speed and cell death.
  • Assessment of ATR and Chk1 expression and activity.
  • Investigation of PrimPol phosphorylation and function.
  • Evaluation of ssDNA gap formation and genomic instability.

Main Results:

  • KRASG12V expression induces RNA transcription-dependent chromatin compaction, leading to replication fork slowing and cell death.
  • Elevated ATR expression is crucial for tolerating KRASG12V-induced replication stress and expanding replication stress-tolerant cells (RSTCs).
  • PrimPol phosphorylation at Ser255, dependent on ATR/Chk1, maintains fork progression and cell survival by promoting repriming.
  • PrimPol-dependent repriming generates ssDNA gaps at heterochromatin, contributing to genomic instability.

Conclusions:

  • ATR and PrimPol play critical roles in enabling precancerous cells to survive KRAS-induced replication stress.
  • This survival mechanism facilitates clonal expansion of cancer cells but is associated with increased genomic instability.
  • Understanding these pathways offers potential therapeutic targets for KRAS-driven cancers.

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