An ATM-PPM1D circuit controls the processing and restart of DNA replication forks.

PPM1D/WIP1 restrains ATM-driven replication stress signaling to prevent excessive MRE11- and DNA2-dependent degradation and enable RAD51-dependent stalled fork restart.

• Why it matters: Replication stress recovery, especially how stalled forks restart, is poorly understood despite known roles for damage signaling in origin inhibition and fork stabilization.
• What they did: The study shows that PPM1D loss during recovery causes defective RAD51 recruitment and impaired RAD51-dependent restart, and phosphoproteomics links PPM1D to an ATM substrate network; ATM inhibition suppresses PPM1D-loss defects.
• The result: ATM hyper-signaling suppresses fork restart partly via excessive 53BP1 engagement and RAD51 antagonization, implying PPM1D promotes proper restart by restraining ATM signaling.

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