ATM is required for the cellular response to thymidine induced replication fork stress

Area of Science:

• Cellular biology
• Molecular oncology
• DNA damage response

Background:

• Cell cycle checkpoints are crucial for genomic stability, responding to DNA replication stress and damage.
• ATM and ATR are key protein kinases regulating cell cycle progression and DNA repair pathways.
• Replication fork stalling can activate distinct signaling pathways to maintain genome integrity.

Purpose of the Study:

• To investigate the DNA damage response induced by thymidine, a dCTP pool depletor.
• To elucidate the roles of ATM and ATR in thymidine-induced cellular responses.
• To determine the involvement of ATM in homologous recombination repair (HRR) following thymidine treatment.

Main Methods:

• Treatment of cells with thymidine to induce replication stress.
• Analysis of protein phosphorylation (Chk1, Chk2, NBS1, SMC1) via Western blotting.
• Assessment of cell viability and homologous recombination repair (HRR) in wild-type and AT cells.
• Utilizing ataxia-telangiectasia (AT) cells to study ATM-dependent pathways.

Main Results:

• Thymidine induces a novel DNA damage response dependent on both ATM and ATR.
• ATM-mediated phosphorylation of Chk2 and NBS1, and ATM-independent phosphorylation of Chk1 and SMC1 were observed.
• AT cells exhibited reduced viability and impaired HRR upon thymidine exposure.
• ATM plays a critical role in the HRR-mediated rescue of thymidine-impaired replication forks.

Conclusions:

• Thymidine elicits a complex DNA damage response requiring both ATM and ATR.
• ATM is implicated in facilitating homologous recombination repair to resolve replication stress caused by thymidine.
• Understanding this pathway is vital for developing strategies against replication-fork-associated genomic instability.