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CHK1-driven histone H3.3 serine 31 phosphorylation is important for chromatin maintenance and cell survival in human

Fiona T M Chang1, F Lyn Chan1, James D R McGhie1

  • 1Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.

Nucleic Acids Research
|February 19, 2015
PubMed

Insights

In ALT cancers, CHK1 kinase activity elevates H3.3S31ph globally, maintaining chromatin integrity. Inhibiting CHK1 in these cells decreases H3.3S31ph, increasing DNA damage and reducing cell survival.

Area of Science:

  • Epigenetics
  • Cancer Biology
  • Chromatin Biology

Background:

  • Alternative Lengthening of Telomeres (ALT) cancers exhibit high mutation rates in ATRX and DAXX.
  • Loss of ATRX/DAXX is known to disrupt H3.3 deposition at heterochromatin.
  • The global impact of ATRX/DAXX loss on H3.3 deposition and post-translational modifications is not well understood.

Purpose of the Study:

  • To investigate the dynamics of phosphorylated H3.3 serine 31 (H3.3S31ph) in human ALT cancer cells.
  • To elucidate the role of CHK1 activity in H3.3S31ph regulation within ALT cells.
  • To determine the functional significance of CHK1-mediated H3.3S31ph in ALT cancer cell survival and chromatin maintenance.

Main Methods:

  • Analysis of H3.3S31ph localization and levels in human ALT cancer cells during mitosis.
  • Pharmacological inhibition of CHK1 activity during mitosis.
  • Expression of a mutant H3.3S31A in ALT cells.
  • Assessment of H2AX serine 139 phosphorylation (H2AXS139ph) levels.
  • Evaluation of cell viability assays.

Main Results:

  • ALT cells display elevated H3.3S31ph across the entire chromosome during mitosis, unlike normal somatic cells where it is restricted to pericentric satellite DNA.
  • This global H3.3S31ph increase in ALT cells is attributed to elevated CHK1 activity.
  • Inhibition of CHK1 or expression of H3.3S31A mutant reduced H3.3S31ph levels, leading to increased H2AXS139ph on chromosome arms and telomeres.
  • CHK1 inhibition significantly reduced ALT cancer cell viability.

Conclusions:

  • CHK1 acts as a novel H3.3S31 kinase.
  • CHK1-mediated H3.3S31ph is crucial for maintaining chromatin integrity in ALT cancer cells.
  • Targeting CHK1 activity represents a potential therapeutic strategy for ALT cancers due to its role in cell survival.

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