View in EDS

RPA-independent activation of the ATR/CHK1 pathway.

Saved in:
Bibliographic Details
Title: RPA-independent activation of the ATR/CHK1 pathway.
Authors: Huang, Min1,2 huangmin429@163.com, Zhu, Dandan1, Chen, Junjie1 jchen8@mdanderson.org
Source: Proceedings of the National Academy of Sciences of the United States of America. 2/10/2026, Vol. 123 Issue 6, p1-10. 22p.
Subjects: Replication fork, Serine/threonine kinases, DNA repair, DNA damage, Cellular signal transduction
Abstract: The ATR/CHK1 pathway governs a crucial intra-S-phase checkpoint that safeguards genome stability under replication stress by stabilizing stalled replication forks and ensuring high-fidelity DNA replication. Traditionally, activation of this pathway is thought to rely on replication protein A (RPA)-coated single-stranded DNA, which recruits the ATR–ATRIP complex to sites of stalling fork, positioning RPA as essential for ATR signaling. In this study, we report a surprising and previously unrecognized phenomenon: acute depletion of RPA2 triggers robust ATR/CHK1 activation through an RPA-independent mechanism. Using 293A and RPE-1 cells engineered with an inducible RPA2-dTAG degron system, we observed increased phosphorylation of CHK1 at Ser296 and Ser345 in the absence of RPA. Notably, this elevated CHK1 phosphorylation was abolished by ATR inhibition, confirming its dependence on ATR kinase activity. Mechanistic analyses further revealed that this RPA-independent activation requires the checkpoint mediators RAD9 and TOPBP1. These findings uncover dual mechanisms, both RPA-dependent and -independent, of ATR/CHK1 pathway activation, highlighting a robust and flexible replication stress response network that preserves genome integrity even when canonical signaling is disrupted. [ABSTRACT FROM AUTHOR]
Copyright of Proceedings of the National Academy of Sciences of the United States of America is the property of National Academy of Sciences and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
Description
Abstract:The ATR/CHK1 pathway governs a crucial intra-S-phase checkpoint that safeguards genome stability under replication stress by stabilizing stalled replication forks and ensuring high-fidelity DNA replication. Traditionally, activation of this pathway is thought to rely on replication protein A (RPA)-coated single-stranded DNA, which recruits the ATR–ATRIP complex to sites of stalling fork, positioning RPA as essential for ATR signaling. In this study, we report a surprising and previously unrecognized phenomenon: acute depletion of RPA2 triggers robust ATR/CHK1 activation through an RPA-independent mechanism. Using 293A and RPE-1 cells engineered with an inducible RPA2-dTAG degron system, we observed increased phosphorylation of CHK1 at Ser296 and Ser345 in the absence of RPA. Notably, this elevated CHK1 phosphorylation was abolished by ATR inhibition, confirming its dependence on ATR kinase activity. Mechanistic analyses further revealed that this RPA-independent activation requires the checkpoint mediators RAD9 and TOPBP1. These findings uncover dual mechanisms, both RPA-dependent and -independent, of ATR/CHK1 pathway activation, highlighting a robust and flexible replication stress response network that preserves genome integrity even when canonical signaling is disrupted. [ABSTRACT FROM AUTHOR]
ISSN:00278424
DOI:10.1073/pnas.2524246123