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XB-ART-52035
J Biol Chem 2016 Jun 17;29125:13124-31. doi: 10.1074/jbc.M116.729194.
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Direct Binding to Replication Protein A (RPA)-coated Single-stranded DNA Allows Recruitment of the ATR Activator TopBP1 to Sites of DNA Damage.

Acevedo J , Yan S , Michael WM .


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A critical event for the ability of cells to tolerate DNA damage and replication stress is activation of the ATR kinase. ATR activation is dependent on the BRCT (BRCA1 C terminus) repeat-containing protein TopBP1. Previous work has shown that recruitment of TopBP1 to sites of DNA damage and stalled replication forks is necessary for downstream events in ATR activation; however, the mechanism for this recruitment was not known. Here, we use protein binding assays and functional studies in Xenopus egg extracts to show that TopBP1 makes a direct interaction, via its BRCT2 domain, with RPA-coated single-stranded DNA. We identify a point mutant that abrogates this interaction and show that this mutant fails to accumulate at sites of DNA damage and that the mutant cannot activate ATR. These data thus supply a mechanism for how the critical ATR activator, TopBP1, senses DNA damage and stalled replication forks to initiate assembly of checkpoint signaling complexes.

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Species referenced: Xenopus laevis
Genes referenced: atr rpa1 topbp1

References [+] :
Ball, ATRIP binding to replication protein A-single-stranded DNA promotes ATR-ATRIP localization but is dispensable for Chk1 phosphorylation. 2005, Pubmed