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Published online 25 December 2000. doi:10.1083/jcb.151.7.1381
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© The Rockefeller University Press, 0021-9525/2000//1381 $5.00
The Journal of Cell Biology, Volume 151, Number 7, , 2000 1381-1390

Original Article

P53 Binding Protein 1 (53bp1) Is an Early Participant in the Cellular Response to DNA Double-Strand Breaks



Linda B. Schultza,b, Nabil H. Chehaba, Asra Malikzaya, and Thanos D. Halazonetisa,c

a Department of Molecular Genetics, The Wistar Institute, Philadelphia, Pennsylvania 19104
b Graduate Program in Cell and Molecular Biology, School of Medicine
c Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
The Wistar Institute, 3601 Spruce St., Philadelphia, PA 19104-4268.(215) 573-9271(215) 898-3789

halazonetis{at}wistar.upenn.edu

p53 binding protein 1 (53BP1), a protein proposed to function as a transcriptional coactivator of the p53 tumor suppressor, has BRCT domains with high homology to the Saccharomyces cerevisiae Rad9p DNA damage checkpoint protein. To examine whether 53BP1 has a role in the cellular response to DNA damage, we probed its intracellular localization by immunofluorescence. In untreated primary cells and U2OS osteosarcoma cells, 53BP1 exhibited diffuse nuclear staining; whereas, within 5–15 min after exposure to ionizing radiation (IR), 53BP1 localized at discreet nuclear foci. We propose that these foci represent sites of processing of DNA double-strand breaks (DSBs), because they were induced by IR and chemicals that cause DSBs, but not by ultraviolet light; their peak number approximated the number of DSBs induced by IR and decreased over time with kinetics that parallel the rate of DNA repair; and they colocalized with IR-induced Mre11/NBS and {gamma}-H2AX foci, which have been previously shown to localize at sites of DSBs. Formation of 53BP1 foci after irradiation was not dependent on ataxia-telangiectasia mutated (ATM), Nijmegen breakage syndrome (NBS1), or wild-type p53. Thus, the fast kinetics of 53BP1 focus formation after irradiation and the lack of dependency on ATM and NBS1 suggest that 53BP1 functions early in the cellular response to DNA DSBs.

Key Words: 53BP1 • p53 • DNA damage • ionizing radiation • cancer

© 2000 The Rockefeller University Press

Abbreviations used in this paper: A-T, ataxia-telangiectasia; ATM, A-T mutated protein; ATR, ATM- and Rad3-related protein; 53BP1, p53 binding protein 1; DNA-PK, DNA-dependent protein kinase; DSB, double-strand break; HA, hemagglutinin; HU, hydroxyurea; IR, ionizing radiation; NBS, Nijmegen breakage syndrome; ORF, open reading frame; PML, promyelocytic leukemia.


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J. Cell Biol. 2000 151: 0-2. [Full Text] [PDF]





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