title: gammaH2A binds Brc1 to maintain genome integrity during S-phase.
abstract: ATM(Tel1) and ATR(Rad3) checkpoint kinases phosphorylate the C-terminus of histone H2AX (H2A in yeasts) in chromatin flanking DNA damage, establishing a recruitment platform for checkpoint and repair proteins. Phospho-H2A/X (gammaH2A/X)-binding proteins at double-strand breaks (DSBs) have been characterized, but those required for replication stress responses are unknown. Here, we present genetic, biochemical, small angle X-ray scattering (SAXS), and X-ray structural studies of the Schizosaccharomyces pombe Brc1, a 6-BRCT-domain protein that is structurally related to Saccharomyces cerevisiae Rtt107 and mammalian PTIP. Brc1 binds gammaH2A to form spontaneous and DNA damage-induced nuclear foci. Spontaneous Brc1 foci colocalize with ribosomal DNA repeats, a region prone to fork pausing and genomic instability, whereas DNA damage-induced Brc1 foci colocalize with DSB response factors. gammaH2A binding is critical for Brc1 function. The 1.45 A resolution crystal structure of Brc1-gammaH2A complex shows how variable BRCT insertion loops sculpt tandem-BRCT phosphoprotein-binding pockets to facilitate unique phosphoprotein-interaction specificities, and unveils an acidic DNA-mimicking Brc1 surface. From these results, Brc1 docking to gammaH2A emerges as a critical chromatin-specific response to replication-associated DNA damage.
authors.affiliation: Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA.
authors.forename: Jessica S
authors.initials: JS
authors.lastname: Williams
authors.forename: R Scott
authors.initials: RS
authors.lastname: Williams
authors.forename: Claire L
authors.initials: CL
authors.lastname: Dovey
authors.forename: Grant
authors.initials: G
authors.lastname: Guenther
authors.forename: John A
authors.initials: JA
authors.lastname: Tainer
authors.forename: Paul
authors.initials: P
authors.lastname: Russell
mesh_terms: D018360:Crystallography, X-Ray; D004249:DNA Damage; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D016196:S Phase; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C511286:Brc1 protein, S pombe; D006657:Histones; D029702:Schizosaccharomyces pombe Proteins