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1: Cell. 2006 Mar 10;124(5):943-55.
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TopBP1 activates the ATR-ATRIP complex.

Kumagai A, Lee J, Yoo HY, Dunphy WG.

Division of Biology 216-76, California Institute of Technology, Pasadena, CA 91125, USA.

ATR is a key regulator of checkpoint responses to incompletely replicated and damaged DNA, but the mechanisms underlying control of its kinase activity are unknown. TopBP1, the vertebrate homolog of yeast Cut5/Dbp11, has dual roles in initiation of DNA replication and regulation of checkpoint responses. We show that recombinant TopBP1 induces a large increase in the kinase activity of both Xenopus and human ATR. The ATR-activating domain resides in a conserved segment of TopBP1 that is distinct from its numerous BRCT repeats. The isolated ATR-activating domain from TopBP1 induces ectopic activation of ATR-dependent signaling in both Xenopus egg extracts and human cells. Furthermore, Xenopus egg extracts containing a version of TopBP1 with an inactivating point mutation in the ATR-activating domain are defective in checkpoint regulation. These studies establish that activation of ATR by TopBP1 is a crucial step in the initiation of ATR-dependent signaling processes.

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PMID: 16530042 [PubMed - indexed for MEDLINE]