PRIMPOL-Mediated Adaptive Response Suppresses Replication Fork Reversal in BRCA-Deficient Cells

Area of Science:

• Molecular Biology
• Cancer Research
• DNA Replication

Background:

• Replication-stalling chemotherapeutics like cisplatin can cause DNA replication fork reversal.
• BRCA proteins are crucial for protecting reversed forks from degradation; their deficiency increases chemosensitivity.
• Understanding cellular responses to repeated drug exposure is vital for optimizing cancer treatment.

Purpose of the Study:

• To investigate the mechanisms by which cancer cells adapt to multiple doses of cisplatin.
• To elucidate the role of PRIMPOL in protecting DNA replication forks during chronic chemotherapy exposure.
• To explore the potential of targeting the PRIMPOL pathway for modulating cisplatin chemosensitivity.

Main Methods:

• Utilized BRCA1-deficient cancer cell models.
• Administered multiple doses of cisplatin to mimic clinical treatment.
• Employed electron microscopy and single-molecule DNA fiber analyses.
• Assessed PRIMPOL expression, chromatin loading, and ATR activity.

Main Results:

• Fork degradation was undetectable in BRCA1-deficient cells after multiple cisplatin doses.
• This adaptation was dependent on increased PRIMPOL expression and chromatin association, regulated by ATR.
• PRIMPOL reinitiated DNA synthesis past lesions, suppressing fork reversal and leading to ssDNA gaps.
• This repriming mechanism allows cells to survive repeated cisplatin exposure.

Conclusions:

• Cells adapt to chronic cisplatin treatment by activating PRIMPOL-mediated repriming of DNA replication forks.
• This adaptive response suppresses pathological fork reversal and degradation, contributing to chemoresistance.
• Targeting the PRIMPOL pathway presents a novel strategy to overcome resistance and enhance cisplatin efficacy in cancer therapy.