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Uncoupling of RAD51 focus formation and cell survival after replication fork stalling in RAD51D null CHO cells
Salustra S Urbin1, Ingegerd Elvers, John M Hinz
1Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Environmental and Molecular Mutagenesis
|February 4, 2012
Summary
RAD51D protein is crucial for homologous recombination repair (HRR) and DNA repair. RAD51D deficient cells show normal resistance to DNA replication inhibitors, but are sensitive to PARP1 inhibitors, indicating unequal paralog contributions to DNA replication stress resistance.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Homologous recombination repair (HRR) is vital for DNA double-strand break (DSB) repair in vertebrate cells.
- RAD51 paralogs (XRCC2/3, RAD51B/C/D) are key components enhancing HRR efficiency.
- Replication fork stalling and breakage can lead to genomic instability and cell death.
Purpose of the Study:
- To assess the role of RAD51D in cellular resistance to replication-associated DSBs.
- To investigate the contribution of RAD51 paralogs to resistance against DNA replication inhibitors.
- To evaluate the correlation between RAD51 focus formation and cellular resistance.
Main Methods:
- Utilized isogenic RAD51D-null CHO and XRCC2-mutant V79 cell lines.
- Exposed cells to replication inhibitors (hydroxyurea, aphidicolin) and camptothecin.
- Assessed cellular resistance to killing and RAD51 focus formation.
- Tested sensitivity to the PARP1 inhibitor KU58684.
Main Results:
- RAD51D-null cells exhibited normal resistance to hydroxyurea and aphidicolin despite lacking HRR initiation.
- These cells showed expected sensitivity to camptothecin.
- RAD51D-null cells displayed extreme sensitivity to the PARP1 inhibitor KU58684, with defective RAD51 focus formation.
- XRCC2-mutant cells showed increased sensitivity to hydroxyurea under certain conditions, correlated with reduced RAD51 foci.
Conclusions:
- RAD51 paralogs do not have equal roles in conferring resistance to DNA replication inhibitors.
- RAD51 focus formation in response to replication stress may not reliably predict cellular resistance.
- RAD51D plays a significant role in resistance to PARP1 inhibition, linked to HRR pathway function.
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