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Reduced expression of GINS complex members induces hallmarks of pre-malignancy in primary untransformed human cells

Laura R Barkley1, Ihn Young Song, Ying Zou

  • 1Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA, USA.

Cell Cycle (Georgetown, Tex.)
|April 21, 2009
PubMed

Insights

Depleting the GINS complex (Psf1/Psf2) in human cells causes DNA replication stress and damage, not direct mitotic issues. This damage response helps maintain chromosome integrity.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • The GINS complex is crucial for DNA replication initiation and elongation.
  • Psf2 depletion in cancer cells causes chromosome mis-segregation, but its role in normal cells is unclear.
  • Untransformed Human Dermal Fibroblasts (HDF) were used to investigate the GINS complex's function.

Purpose of the Study:

  • To investigate the precise role of the GINS complex, specifically Psf2, in mitosis and DNA replication in untransformed human cells.
  • To determine if Psf2 depletion affects DNA replication and if this leads to cell cycle delays.
  • To examine the cellular response to replication stress and DNA damage induced by Psf2 depletion.

Main Methods:

  • Synchronized cultures of Human Dermal Fibroblasts (HDF) with Psf1/Psf2 depletion were analyzed.
  • Metaphase spreads were examined for chromosomal abnormalities.
  • DNA replication markers (Mcm7, Cdc45, PCNA), cell cycle progression (G2/M markers), and DNA damage markers (gammaH2AX, pChk2) were assessed.
  • The effect of inhibiting Chk2 on cell cycle progression was evaluated.

Main Results:

  • Psf1/Psf2 depletion did not cause major mitotic defects or chromosome mis-segregation in HDF.
  • Replication licensing (Mcm7 chromatin binding) was unaffected, but DNA synthesis initiation (Cdc45, PCNA binding) and S-phase progression were delayed.
  • Psf1/Psf2-depleted cells exhibited hallmarks of replication stress and DNA damage, including gammaH2AX and Thr 68-phosphorylated Chk2.
  • Inhibition of Chk2 partially rescued S-phase and G2/M progression, indicating its role in the delay.

Conclusions:

  • The GINS complex (Psf1/Psf2) is not directly required for mitosis in untransformed human cells.
  • Psf1/Psf2 depletion leads to replication stress and DNA damage during S-phase.
  • Chk2-mediated DNA damage signaling is activated and contributes to maintaining chromosomal integrity under these conditions.

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