Abstract
Rad9, Rad1, and Hus1 form a heterotrimeric complex (9-1-1) that is loaded onto DNA at sites of DNA damage. DNA-loaded 9-1-1 activates signaling through the Chk1 arm of the DNA damage checkpoint response via recruitment and stimulation of ATR. Additionally, 9-1-1 may play a direct role in facilitating DNA damage repair via interaction with a number of DNA repair enzymes. We have now determined the crystal structure of the human 9-1-1 complex, revealing a toroidal structure with a similar architecture to the homotrimeric PCNA DNA-binding clamp. The structure explains the formation of a unique heterotrimeric arrangement and reveals significant differences among the three subunits in the sites implicated in binding to the clamp loader and to ligand proteins. Biochemical analysis reveals a single repair enzyme-binding site on 9-1-1 that can be blocked competitively by the PCNA-binding cell-cycle regulator p21(cip1/waf1).
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Binding Sites
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Cell Cycle Proteins / chemistry*
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism
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Crystallography, X-Ray
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Cyclin-Dependent Kinase Inhibitor p15 / metabolism
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Cyclin-Dependent Kinase Inhibitor p21 / metabolism
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DNA Damage*
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DNA Repair
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Evolution, Molecular
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Exonucleases / chemistry*
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Exonucleases / genetics
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Exonucleases / metabolism
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Flap Endonucleases / metabolism
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Humans
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Models, Molecular
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Phylogeny
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Protein Processing, Post-Translational
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Protein Structure, Quaternary
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Protein Subunits / chemistry
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Protein Subunits / genetics
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Protein Subunits / metabolism
Substances
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CDKN1A protein, human
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CDKN2B protein, human
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Cell Cycle Proteins
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Cyclin-Dependent Kinase Inhibitor p15
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Cyclin-Dependent Kinase Inhibitor p21
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HUS1 protein, human
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HUS1B protein, human
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Protein Subunits
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rad9 protein
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Exonucleases
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Flap Endonucleases
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FEN1 protein, human
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Rad1 protein, human