TopBP1, also termed DNA topoisomerase II-beta-binding protein 1, functions in DNA replication and damage response. It binds double-stranded DNA breaks and nicks as well as single-stranded DNA [1-4]. It consists of multiple copies of BRCT domains, with a triple tandem BRCT domains at the N-terminal (designated BRCT0, BRCT1 and BRCT2), also observed in ECT2 that may represent a new type of consecutive BRCT domains [1-3]. This entry represents the first BRCT domain (BRCT0) of TopBP1 [1-4]. BRCT1/2 are included in Pfam:PF00533. Although ECT2 and TopBP1 share a similar cylinder-like crystal structure and distribution of secondary structure, some helices exhibit different orientations especially in the BRCT0 domain.

1: Structure and function of the Rad9-binding region of the DNA-damage checkpoint adaptor TopBP1. Rappas M, Oliver AW, Pearl LH; Nucleic Acids Res. 2011;39:313-324. PMID:20724438

2: Crystal structure of the N-terminal region of human Topoisomerase IIbeta binding protein 1. Huo YG, Bai L, Xu M, Jiang T; Biochem Biophys Res Commun. 2010;401:401-405. PMID:20858457

3: Crystal structure of triple-BRCT-domain of ECT2 and insights into the binding characteristics to CYK-4. Zou Y, Shao Z, Peng J, Li F, Gong D, Wang C, Zuo X, Zhang Z, Wu J, Shi Y, Gong Q; FEBS Lett. 2014;588:2911-2920. PMID:25068414

4: BRCT domains of the DNA damage checkpoint proteins TOPBP1/Rad4 display distinct specificities for phosphopeptide ligands. Day M, Rappas M, Ptasinska K, Boos D, Oliver AW, Pearl LH; Elife. 2018; [Epub ahead of print] PMID:30295604