Related Experiment Video

Updated: Jun 27, 2026

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
10:27

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

Published on: March 9, 2012

Rac1 GTPase Regulates the SCFβTrCP-Mediated Degradation of Claspin and the Cellular Response of Pancreatic Cancer

Neha Chaudhary1,2, Tabbatha N Somers1, Surinder K Batra2

  • 1Department Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68198, USA.

Cancers
|June 26, 2026
PubMed
Abstract

Insights

Rac1 inhibition degrades Claspin, impairing DNA damage response in pancreatic cancer cells. This sensitizes cancer cells, but not normal cells, to radiation therapy by disrupting ATR/Chk1 signaling.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Signaling

Background:

  • Pancreatic ductal adenocarcinomas (PDACs) are lethal and resistant to therapies.
  • The KRAS oncogene drives PDAC, with tumors reliant on its effectors like Rac1.
  • Rac1 regulates DNA damage response and actin remodeling.

Purpose of the Study:

  • Investigate Rac1's role in DNA damage response pathways in PDAC.
  • Determine the mechanism by which Rac1 inhibition affects ATR/Chk1 signaling.
  • Assess the therapeutic potential of targeting Rac1 in PDAC.

Main Methods:

  • Western blot analysis to study ATR/Chk1 cascade components.
  • Rac1 inhibition using chemical inhibitors and siRNA.
  • Assessment of Claspin protein levels, mRNA, and half-life.
  • Analysis of proteasomal degradation and involvement of βTrCP1/2.

Main Results:

  • Rac1 inhibition decreases Claspin protein levels by promoting its degradation.
  • Claspin degradation is proteasome- and βTrCP1/2-dependent in PDAC cells.
  • PDAC cells are more vulnerable to Claspin depletion and gamma-ray-induced apoptosis than normal cells.
  • Rac1 inhibition impairs Chk1 activation in response to DNA damage.

Conclusions:

  • Rac1 is crucial for stabilizing Claspin, a key component of the fork protection complex.
  • Rac1 inhibition leads to βTrCP-dependent degradation of Claspin, hindering Chk1 activation.
  • Targeting Rac1 sensitizes PDAC cells to DNA-damaging agents by disrupting ATR/Chk1 signaling.
Keywords:
ATRChk1ClaspinGTPaseRac1pancreatic cancerubiquitin ligasesβTrCP

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