Published online May 26, 2008
doi:10.1083/jcb.200801083
The Journal of Cell Biology, Vol. 181, No. 5, 727-735
The Rockefeller University Press, 0021-9525 $30.00
© 2008 Minter-Dykhouse et al.
Distinct versus overlapping functions of MDC1 and 53BP1 in DNA damage response and tumorigenesis
Katherine Minter-Dykhouse1,
Irene Ward1,
Michael S.Y. Huen2,
Junjie Chen2, and
Zhenkun Lou1
1 Division of Oncology Research, Mayo Clinic, Rochester, MN 55905
2 Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520
Correspondence to Junjie Chen: Junjie.Chen{at}yale.edu; or Zhenkun Lou: Lou.Zhenkun{at}mayo.edu
The importance of the DNA damage response (DDR) pathway in development, genomic stability, and tumor suppression is well recognized. Although 53BP1 and MDC1 have been recently identified as critical upstream mediators in the cellular response to DNA double-strand breaks, their relative hierarchy in the ataxia telangiectasia mutated (ATM) signaling cascade remains controversial. To investigate the divergent and potentially overlapping functions of MDC1 and 53BP1 in the ATM response pathway, we generated mice deficient for both genes. Unexpectedly, the loss of both MDC1 and 53BP1 neither significantly increases the severity of defects in DDR nor increases tumor incidence compared with the loss of MDC1 alone. We additionally show that MDC1 regulates 53BP1 foci formation and phosphorylation in response to DNA damage. These results suggest that MDC1 functions as an upstream regulator of 53BP1 in the DDR pathway and in tumor suppression.
Abbreviations used in this paper: ATM, ataxia telangiectasia mutated; BRCT, BRCA1 C terminal; CSR, class-switch recombination; DDR, DNA damage response; DKO, double KO; HR, homologous recombination; IR, ionizing radiation; KO, knockout; MEF, mouse embryonic fibroblast; MMC, mitomycin C; WT, wild type.
© 2008 Minter-Dykhouse et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jcb.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).

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