title: Crystal structure of the N-terminal region of human Topoisomerase IIβ binding protein 1.
abstract: Human DNA Topoisomerase IIβ binding protein 1 (TopBP1) is a modulating protein that plays an essential role in the response to DNA damage. The N-terminal region of TopBP1, which contains predicted BRCA1-carboxy terminal (BRCT) domains 1 and 2, binds to Rad9, a component of the cell cycle checkpoint clamp Rad9-Hus1-Rad1 complex. Here, we report the crystal structure of the TopBP1N-terminal region (residues 1-290) at 2.4Å resolution. Interestingly, in addition to the predicted tandem BRCT1-2 repeats (residues 103-284), residues 7-98 form a previously unreported BRCT domain (here, BRCT0). In contrast to both BRCT1 and BRCT2, which possess the conventional phosphopeptide binding residues within a surface pocket, the corresponding pocket in BRCT0 is largely hydrophobic. Structural comparisons together with peptide binding studies indicate that the tandem BRCT1-2 domains are the binding region for phosphorylated Ser387 in Rad9.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China.
authors.forename: Yan-Gao
authors.initials: YG
authors.lastname: Huo
authors.forename: Lin
authors.initials: L
authors.lastname: Bai
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.forename: Tao
authors.initials: T
authors.lastname: Jiang
mesh_terms: D019313:BRCA1 Protein / Q000737:chemistry; D024682:BRCA2 Protein / Q000737:chemistry; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry*; D004791:Enzyme Inhibitors / Q000737:chemistry; D006801:Humans; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry*; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012694:Serine / Q000737:chemistry / Q000378:metabolism
chemical_list: D019313:BRCA1 Protein; D024682:BRCA2 Protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; C110513:TOPBP1 protein, human; D012694:Serine