Tipin-Replication Protein A Interaction Mediates Chk1 Phosphorylation by ATR in Response to Genotoxic Stress |
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| Authors: | Michael G Kemp Zafer Akan Se?il Yilmaz Mary Grillo Stephanie L Smith-Roe Tae-Hong Kang Marila Cordeiro-Stone William K Kaufmann Robert T Abraham Aziz Sancar Keziban ünsal-Ka?maz |
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| Institution: | From the Departments of ‡Biochemistry and Biophysics and ;‖Pathology and Laboratory Medicine.;**Center for Environmental Health and Susceptibility, and ;§Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599 and ;the ¶Center for Integrative Biology and Biotherapeutics, Pfizer Biopharmaceuticals, Pearl River, New York 10965 |
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| Abstract: | Mammalian Timeless is a multifunctional protein that performs essential roles in the circadian clock, chromosome cohesion, DNA replication fork protection, and DNA replication/DNA damage checkpoint pathways. The human Timeless exists in a tight complex with a smaller protein called Tipin (Timeless-interacting protein). Here we investigated the mechanism by which the Timeless-Tipin complex functions as a mediator in the ATR-Chk1 DNA damage checkpoint pathway. We find that the Timeless-Tipin complex specifically mediates Chk1 phosphorylation by ATR in response to DNA damage and replication stress through interaction of Tipin with the 34-kDa subunit of replication protein A (RPA). The Tipin-RPA interaction stabilizes Timeless-Tipin and Tipin-Claspin complexes on RPA-coated ssDNA and in doing so promotes Claspin-mediated phosphorylation of Chk1 by ATR. Our results therefore indicate that RPA-covered ssDNA not only supports recruitment and activation of ATR but also, through Tipin and Claspin, it plays an important role in the action of ATR on its critical downstream target Chk1. |
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| Keywords: | Cell Cycle Checkpoint Control DNA Damage DNA-Protein Interaction Signal Transduction |
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