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Author Joo, Woo Seong
Title Structures of tandem-BRCT domains and their complexes: Structure of 53BP1 tandem-BRCT region bound top53 DNA-binding domain and comparison with structure of rat Brca1 tandem-BRCT region. Structure of human Brca1 tandem-BRCT region bound to Bach1 phosphoseryl peptide
book jacket
Descript 100 p
Note Source: Dissertation Abstracts International, Volume: 66-03, Section: B, page: 1303
Adviser: Nikola P. Pavletich
Thesis (Ph.D.)--Weill Medical College of Cornell University, 2005
BRCT is one of the most prevalent protein-protein interaction motifs in proteins involved in DNA-damage response processes. BRCT-containing proteins have important roles in DNA-damage-induced cell cycle checkpoint controls, DNA damage signaling, DNA recombination, and DNA repair. BRCT domains occur as single or tandem-BRCT units, and are often flanked by other functional domains, including additional BRCT domains. Before I began these studies, only a single BRCT structure from XRCC1 was determined, but it revealed little about how the covalently linked BRCT repeats fold together or how they interact with other proteins. Also, recent experiments showed that at least a subset of BRCT-mediated protein-protein interactions are phosphorylation-dependent, which has important implications in DNA-damage-induced cell cycle checkpoint control, signaling and protein assemblies for processing DNA. To understand how tandem-BRCT repeats are arranged structurally to mediate specific protein-protein interactions, I have purified recombinant proteins, crystallized, and determined the structures of (1) 53BP1 tandem-BRCT repeats bound to p53 at 2.5 A resolution, (2) rat Brca1 tandem-BRCT repeats alone at 2.3 A resolution, and (3) human BRCA1 tandem-BRCT repeats bound to a BACH1 phosphoseryl peptide at 2.5 A resolution. These structures show that two BRCT repeats pack interdependently in a near-linear array, and form an interface between the two repeats that is stabilized by the inter-repeat linker. Comparison of the tandem-BRCT structures from 53BP1, rat Brca1, and human BRCA1 reveals that the spatial arrangements of the two BRCT domains and the inter-BRCT interfaces are remarkably similar. The 53BP1-p53 complex structure shows that the first BRCT repeat and the linker of 53BP1 form an interface that packs extensively and overlaps with the L2/L3 loop portion of the DNA-binding surface of p53. The BRCA1 (tandem-BRCT)-BACH1 complex structure shows that a polar pocket in the first BRCT repeat that requires a conserved serine and a lysine binds to pSer990 of BACH1, and a second hydrophobic pocket in between the two BRCT domains binds to Phe993 (pSer+3) of BACH1. A structural comparison with 53BP1 shows that 53BP1 has similar, but not identical, phosphopeptide-binding pockets, lacking the BACH1-binding loop found in the second pocket of the BRCA1 tandem-BRCT region. Thus, these studies show how tandem-BRCT domains bind specifically to other proteins by at least two distinct modes, and provide a structural paradigm for how tandem-BRCT domains mediate protein assembly and organize signals to affect DNA damage response processes in a spatially and temporally regulated manner
School code: 0967
Host Item Dissertation Abstracts International 66-03B
Subject Biology, Molecular
Alt Author Weill Medical College of Cornell University
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