title: Negative cell cycle regulation and DNA damage-inducible phosphorylation of the BRCT protein 53BP1.
abstract: In a screen designed to discover suppressors of mitotic catastrophe, we identified the Xenopus ortholog of 53BP1 (X53BP1), a BRCT protein previously identified in humans through its ability to bind the p53 tumor suppressor. X53BP1 transcripts are highly expressed in ovaries, and the protein interacts with Xp53 throughout the cell cycle in embryonic extracts. However, no interaction between X53BP1 and Xp53 can be detected in somatic cells, suggesting that the association between the two proteins may be developmentally regulated. X53BP1 is modified via phosphorylation in a DNA damage-dependent manner that correlates with the dispersal of X53BP1 into multiple foci throughout the nucleus in somatic cells. Thus, X53BP1 can be classified as a novel participant in the DNA damage response pathway. We demonstrate that X53BP1 and its human ortholog can serve as good substrates in vitro as well as in vivo for the ATM kinase. Collectively, our results reveal that 53BP1 plays an important role in the checkpoint response to DNA damage, possibly in collaboration with ATM.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Texas Health Sciences Center, Houston 77030, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Xia
authors.forename: J C
authors.initials: JC
authors.lastname: Morales
authors.forename: W G
authors.initials: WG
authors.lastname: Dunphy
authors.forename: P B
authors.initials: PB
authors.lastname: Carpenter
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D019313:BRCA1 Protein; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics*; D018797:Cell Cycle Proteins; D003001:Cloning, Molecular; D004249:DNA Damage / Q000235:genetics*; D004268:DNA-Binding Proteins; D015723:Gene Library; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D010750:Phosphoproteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013489:Suppression, Genetic; D025521:Tumor Suppressor Proteins; D014981:Xenopus / Q000235:genetics*
chemical_list: D019313:BRCA1 Protein; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases