title: A DNA damage-regulated BRCT-containing protein, TopBP1, is required for cell survival.
abstract: BRCA1 carboxyl-terminal (BRCT) motifs are present in a number of proteins involved in DNA repair and/or DNA damage-signaling pathways. Human DNA topoisomerase II binding protein 1 (TopBP1) contains eight BRCT motifs and shares sequence similarity with the fission yeast Rad4/Cut5 protein and the budding yeast DPB11 protein, both of which are required for DNA damage and/or replication checkpoint controls. We report here that TopBP1 is phosphorylated in response to DNA double-strand breaks and replication blocks. TopBP1 forms nuclear foci and localizes to the sites of DNA damage or the arrested replication forks. In response to DNA strand breaks, TopBP1 phosphorylation depends on the ataxia telangiectasia mutated protein (ATM) in vivo. However, ATM-dependent phosphorylation of TopBP1 does not appear to be required for focus formation following DNA damage. Instead, focus formation relies on one of the BRCT motifs, BRCT5, in TopBP1. Antisense Morpholino oligomers against TopBP1 greatly reduced TopBP1 expression in vivo. Similar to that of ataxia telangiectasia-related protein (ATR), Chk1, or Hus1, downregulation of TopBP1 leads to reduced cell survival, probably due to increased apoptosis. Taken together, the data presented here suggest that, like its putative counterparts in yeast species, TopBP1 may be involved in DNA damage and replication checkpoint controls.
authors.affiliation: Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Yamane
authors.forename: Xianglin
authors.initials: X
authors.lastname: Wu
authors.forename: Junjie
authors.initials: J
authors.lastname: Chen
mesh_terms: D020816:Amino Acid Motifs; D064007:Ataxia Telangiectasia Mutated Proteins; D019313:BRCA1 Protein / Q000737:chemistry / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology*; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication; D004268:DNA-Binding Proteins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D020014:K562 Cells; D009687:Nuclear Proteins / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000235:genetics / Q000494:pharmacology; D010750:Phosphoproteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins; D000071857:Tumor Suppressor p53-Binding Protein 1
chemical_list: D019313:BRCA1 Protein; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D010750:Phosphoproteins; C110513:TOPBP1 protein, human; C498301:TP53BP1 protein, human; D025521:Tumor Suppressor Proteins; D000071857:Tumor Suppressor p53-Binding Protein 1; C576897:Atr protein, mouse; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases