ATR Signaling Uncouples the Role of RAD51 Paralogs in Homologous Recombination and Replication Stress Response

Sneha Saxena,Suruchi Dixit,Kumar Somyajit,Ganesh Nagaraju

doi:10.1016/j.celrep.2019.09.008

Sneha Saxena, Suruchi Dixit + Show 2 more

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https://doi.org/10.1016/j.celrep.2019.09.008

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Journal: Cell Reports	Publication Date: Oct 1, 2019
Citations: 29	License type: cc-by

Affiliation: Indian Institute of Science Bangalore

Abstract

ATR kinase-mediated replication checkpoint is vital for genome maintenance following replication stress. Previously, we showed that XRCC2-RAD51D (DX2) sub-complex of RAD51 paralogs restrains active DNA synthesis during dNTP alterations, in a manner dependent on ATR-mediated phosphorylation of XRCC2. Here, we find that unrestrained fork progression in XRCC2 deficiency and phosphorylation defect causes replication-associated errors, subsequently resulting in genome-wide double-strand breaks (DSBs) and early activation of ATM signaling. Cells defective in XRCC2 phosphorylation exhibit ATM/ATR-mediated early activation of XRCC3 during perturbed replication, which facilitates recombination-mediated repair of the post-replicative DNAdamage and thereby promotes cell viability. Collectively, our findings identify collaborative roles of RAD51 paralog complexes during replication stress and reveal their differential regulation by ATRsignaling to promote cell survival and genome integrity.

Highlights

During DNA replication, various types of impediments cause slowing or stalling of the replication forks, leading to replication stress, which is a major driver of tumor progression (Techer et al, 2017; Zeman and Cimprich, 2014)
Mammalian RAD51 paralogs are a family of conserved proteins (RAD51B, RAD51C, RAD51D, XRCC2, and XRCC3) that are involved in homologous recombination (HR) (Somyajit et al, 2010; Suwaki et al, 2011), DNA damage signaling (Badie et al, 2009; Somyajit et al, 2012, 2013), protection and restart of stalled replication forks (Somyajit et al, 2015), and mitochondrial genome stability (Mishra et al, 2018)
Unrestrained DNA Replication in XRCC2 PhosphoDefective Cells Induces Post-Replicative singlestranded DNA (ssDNA) Gaps XRCC2-RAD51D (DX2) complex of RAD51 paralogs was recently shown to be involved in restraining active fork

Summary

Introduction

During DNA replication, various types of impediments cause slowing or stalling of the replication forks, leading to replication stress, which is a major driver of tumor progression (Techer et al, 2017; Zeman and Cimprich, 2014). A RAD51 paralog sub-complex (DX2) was recently found to be involved in aligning the rate of fork progression with cellular dNTP pool alterations. This function was regulated through ATR-mediated phosphorylation of XRCC2, implicating the paralogs as key components of the replication stress response (Saxena et al, 2018). Another RAD51 paralog, XRCC3, was identified as a target of ATR kinase, but in response to DSBs (Somyajit et al, 2013). The activation and cellular functions of these phosphorylation events have been deciphered in the context of individual complexes, whether these two signaling pathways functionally interact remains elusive

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