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Regulation of ETAA1-mediated ATR activation couples DNA replication fidelity and genome stability.

ABSTRACT: The ATR kinase is a master regulator of the cellular response to DNA replication stress. Activation of ATR relies on dual pathways involving the TopBP1 and ETAA1 proteins, both of which harbor ATR-activating domains (AADs). However, the exact contribution of the recently discovered ETAA1 pathway to ATR signaling in different contexts remains poorly understood. Here, using an unbiased CRISPR-Cas9-based genome-scale screen, we show that the ATR-stimulating function of ETAA1 becomes indispensable for cell fitness and chromosome stability when the fidelity of DNA replication is compromised. We demonstrate that the ATR-activating potential of ETAA1 is controlled by cell cycle- and replication stress-dependent phosphorylation of highly conserved residues within its AAD, and that the stimulatory impact of these modifications is required for the ability of ETAA1 to prevent mitotic chromosome abnormalities following replicative stress. Our findings suggest an important role of ETAA1 in protecting against genome instability arising from incompletely duplicated DNA via regulatory control of its ATR-stimulating potential.

SUBMITTER: Achuthankutty D

PROVIDER: S-EPMC6891097 | biostudies-literature |

REPOSITORIES: biostudies-literature

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RPA-coated single-stranded DNA promotes the ETAA1-dependent activation of ATR.

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RPA-Binding Protein ETAA1 Is an ATR Activator Involved in DNA Replication Stress Response.

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A requirement for replication in activation of the ATR-dependent DNA damage checkpoint.

Project description:Using the Xenopus egg extract system, we investigated the involvement of DNA replication in activation of the DNA damage checkpoint. We show here that DNA damage slows replication in a checkpoint-independent manner and is accompanied by replication-dependent recruitment of ATR and Rad1 to chromatin. We also find that the replication proteins RPA and Polalpha accumulate on chromatin following DNA damage. Finally, damage-induced Chk1 phosphorylation and checkpoint arrest are abrogated when replication is inhibited. These data indicate that replication is required for activation of the DNA damage checkpoint and suggest a unifying model for ATR activation by diverse lesions during S phase.

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Activation of the ATR kinase by the RPA-binding protein ETAA1

Project description:The ATR kinase is a master regulator of cellular responses to DNA damage and replication stress that is activated by a complex mechanism involving its binding partner ATRIP, RPA-coated ssDNA, the 9-1-1 complex and TopBP1. Here, we discovered a new ATR activation mechanism in human cells, mediated by the uncharacterized protein ETAA1 (Ewing’s tumor-associated antigen 1). From a comprehensive proteomic survey of protein recruitment to DNA double-strand break-modified chromatin, we identified ETAA1 as a factor that accumulates at DNA damage sites via an RPA-binding motif, and which has an important role in promoting cell survival and preventing replication fork breakage after genotoxic insults. Mechanistically, we show that ETAA1 harbors a conserved domain that potently and directly stimulates ATR kinase activity independent of TopBP1 and 9-1-1, and which is essential for the function of ETAA1 in the DNA damage response. Consistently, ablation of ETAA1 shows profound synthetic lethality with TopBP1 knockdown, resulting from massive replication fork collapse and abrogation of ATR-dependent signaling. Finally, we show that ETAA1 levels in cancer cell lines inversely correlate with their dependency on TopBP1 for ATR activation, and that overexpression of ETAA1 partially restores ATR-dependent signaling after loss of TopBP1. Together, these findings establish a new mechanism of ATR activation in human cells that operates in parallel with, but independent of, the canonical TopBP1-mediated pathway.

2016-09-30 | PXD003529 | Pride

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