Abstract
DNA replication stress triggers the activation of Checkpoint Kinase 1 (Chk1) in a pathway that requires the independent chromatin loading of the ATRIP-ATR (ATR-interacting protein/ATM [ataxia-telangiectasia mutated]-Rad3-related kinase) complex and the Rad9-Hus1-Rad1 (9-1-1) clamp. We show that Rad9's role in Chk1 activation is to bind TopBP1, which stimulates ATR-mediated Chk1 phosphorylation via TopBP1's activation domain (AD), a domain that binds and activates ATR. Notably, fusion of the AD to proliferating cell nuclear antigen (PCNA) or histone H2B bypasses the requirement for the 9-1-1 clamp, indicating that the 9-1-1 clamp's primary role in activating Chk1 is to localize the AD to a stalled replication fork.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cell Line
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Checkpoint Kinase 1
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Chickens
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DNA Replication
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Exonucleases / genetics
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Exonucleases / metabolism*
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Humans
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Models, Biological
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Protein Kinases / genetics
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Protein Kinases / metabolism
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Signal Transduction
Substances
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Carrier Proteins
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Cell Cycle Proteins
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DNA-Binding Proteins
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HUS1 protein, human
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HUS1B protein, human
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Nuclear Proteins
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Rad17 protein, human
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TOPBP1 protein, human
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rad9 protein
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Protein Kinases
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CHEK1 protein, human
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Checkpoint Kinase 1
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Exonucleases
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Rad1 protein, human