ATM pathway activation limits R-loop-associated genomic instability in Werner syndrome cells

Area of Science:

• Genetics
• Molecular Biology
• Cancer Research

Background:

• Werner syndrome (WS) results from Werner protein (WRN) deficiency, impacting genome integrity and cancer risk.
• WRN is crucial for replication-fork stability under replication stress.
• WS cells exhibit impaired ATR-mediated CHK1 activation under mild stress, with other repair pathways being unclear.

Purpose of the Study:

• To investigate alternative DNA repair pathways and genomic instability mechanisms in Werner syndrome cells.
• To elucidate the role of ATM signaling and R-loop dynamics in WRN-deficient cells.
• To explore potential therapeutic strategies targeting R-loop formation or XPG in WS.

Main Methods:

• Cellular exposure to aphidicolin to induce replication stress.
• Analysis of ATM and CHK1 phosphorylation.
• Assessment of R-loop accumulation and XPG-dependent cleavage.
• Evaluation of chromosomal instability.
• Chemical inhibition of ATM kinase activity.

Main Results:

• Loss of WRN enhances ATM phosphorylation and CHK1 activation under prolonged replication stress.
• WRN deficiency sensitizes cells to replication-transcription collisions, increasing R-loop accumulation.
• XPG-dependent cleavage of R-loops activates ATM signaling.
• The ATM pathway mitigates chromosomal instability in WS cells.
• Inhibiting ATM exacerbates genomic instability, which is counteracted by suppressing R-loop formation or abrogating XPG.

Conclusions:

• WRN regulates R-loop-associated genomic instability.
• Replication-transcription conflicts contribute to DNA replication defects and disease in WS.
• Targeting R-loop resolution or XPG presents a therapeutic avenue for managing genomic instability in Werner syndrome and potentially other cancers.