title: Crystal structure of the rad9-rad1-hus1 DNA damage checkpoint complex--implications for clamp loading and regulation.
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).
authors.affiliation: CR-UK DNA Repair Enzymes Group, Section of Structural Biology, The Institute of Cancer Research, 237 Fulham Road, Chelsea, SW36JB London, UK.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Doré
authors.forename: Mairi L
authors.initials: ML
authors.lastname: Kilkenny
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Rzechorzek
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Pearl
mesh_terms: D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D050762:Cyclin-Dependent Kinase Inhibitor p15 / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D019143:Evolution, Molecular; D005092:Exonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D045585:Flap Endonucleases / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D010802:Phylogeny; D011499:Protein Processing, Post-Translational; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; C493966:CDKN2B protein, human; D018797:Cell Cycle Proteins; D050762:Cyclin-Dependent Kinase Inhibitor p15; D050759:Cyclin-Dependent Kinase Inhibitor p21; C549605:HUS1 protein, human; C462949:HUS1B protein, human; D021122:Protein Subunits; C069930:rad9 protein; D005092:Exonucleases; D045585:Flap Endonucleases; C468317:FEN1 protein, human; C113574:Rad1 protein, human