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. 2009 Aug 28;35(4):534-41.
doi: 10.1016/j.molcel.2009.06.037.

A selective requirement for 53BP1 in the biological response to genomic instability induced by Brca1 deficiency

Liu Cao  1 , Xioaling Xu, Samuel F Bunting, Jie Liu, Rui-Hong Wang, Longyue L Cao, J Julie Wu, Tie-Nan Peng, Junjie Chen, Andre Nussenzweig, Chu-Xia Deng, Toren Finkel
Affiliations

A selective requirement for 53BP1 in the biological response to genomic instability induced by Brca1 deficiency

Liu Cao et al. Mol Cell. .

Abstract

The molecular pathways leading from genomic instability to cellular senescence and/or cell death remain incompletely characterized. Using mouse embryonic fibroblasts with constitutively increased DNA damage due to the absence of the full-length form of the tumor suppressor Brca1 (Brca1(Delta 11/Delta 11)), we show that deletion of p53 binding protein 1 (53BP1) selectivity abrogates senescence and cell death stimulated by reduced Brca1 activity. Furthermore, the embryonic lethality induced by Brca1 mutation can be alleviated by 53BP1 deletion. Adult Brca1(Delta 11/Delta 11)53BP1(-/-) manifest constitutively high levels of genomic instability, yet age relatively normally, with a surprisingly low incidence of overall tumor formation. Together, these in vitro and in vivo data suggest that 53BP1 is specifically required for the development of premature senescence and apoptosis induced by Brca1 deficiency. These observations may have important implications for Brca1-mediated tumor formation as well as for the molecular pathway leading from genomic instability to organismal aging.

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Figures

Figure 1
Figure 1. Deletion of 53BP1 selectively rescues premature senescence due to reduced Brca1 activity
(A) MEFs derived from Brca1Δ11/ Δ11 embryos rapidly develop morphological evidence for premature senescence including positive SA-βgal staining. (B) Quantification of SA-βgal staining in MEFs derived from the indicated genotypes (mean +/- SD). (C) Levels of p53 protein and its transcriptional target p21 in early passage MEFs. The deletion of 53BP1 appears to inhibit the observed activation of p53 in Brca1Δ11/ Δ11 MEFs. (D) SA-βgal staining of E18 embryos. (E) Sections of brain obtained from WT, Brca1Δ11/ Δ11, or H2AX-/- embryos were assessed for nuclear foci of 53BP1 or level of histone H4 dimethylated lysine 20 (H4K20me2). Nuclei were visualized by DAPI (blue) staining. (F) Observed senescence following exposure to hydrogen peroxide (20 μM) or γ-irradiation (10 Gy) in WT MEFs, or MEFs lacking 53BP1 or p53 (mean +/- SD). (G) Characterization of 53BP1 and γ-H2AX foci in WT or Brca1Δ11/ Δ11 MEFs. Where indicated, WT MEFs were analyzed 3 hours after 10 Gy irradiation (γ-IR). (H) Similar conditions were used to assess for the presence of nuclear foci containing Rad51 and MDC1.
Figure 2
Figure 2. Deletion of 53BP1 selectively rescues Brca1Δ11/ Δ11 mediated cell death
(A) Representative TUNEL staining observed in the brain of E18 embryos. (B) Quantification of apoptosis in WT, Brca1Δ11/ Δ11 or Brca1Δ11/ Δ1153BP1-/- embryos (mean +/- SD). (C) Radiation induced cell death observed in WT, 53BP1-/- and Brca1Δ11/ Δ1153BP1-/- thymocytes was similar. The box in the lower left hand represents non-apoptotic thymocytes and the percentage of such cells is displayed in the lower right hand corner. (D) Analysis of the DDR pathway in basal and irradiated thymocytes bearing the indicated genotype. (E) Cell death (mean +/- SD) in WT, 53BP1-/- or p53-/-MEFs following exposure to hydrogen peroxide (50 μM), doxorubicin (200 ng/ml) and γ-irradiation (15 Gy).
Fig. 3
Fig. 3. Deletion of 53BP1 does not alter Brca1Δ11/ Δ11 mediated genomic instability
(A) Early passage MEFs were assessed for evidence of activation of the DDR pathway including nuclear foci of γ-H2AX and (B) 53BP1. (C) Day E16 brains were analyzed for nuclear foci of γ-H2AX or (D) 53BP1 demonstrating the activation of the DDR pathway in all Brca1Δ11/ Δ11 expressing embryos. (E) Quantification of γ-H2AX activation in WT (black), Brca1Δ11/ Δ11 (red) or Brca1Δ11/ Δ1153BP1-/- (blue) MEFs and embryos (mean +/- SD). (F) Metaphase spreads from B cells obtained from Brca1Δ11/ Δ1153BP1-/- mice. Arrow in left panel denotes the presence of a chromatid break. Right panel demonstrates a chromosomal 12 break at the IgH locus. Chromosomes were stained with probes for the IgH locus (green), a telomere-specific probe (red) and counterstained with DAPI (blue). (G) Percentage of abnormal metaphase spreads (mean +/- SD) obtained from adult B cells with the indicated genotype (n= 3 animals per genotype with at least 50 metaphase spreads per animal).
Figure 4
Figure 4. Deletion of 53BP1 rescues the premature aging phenotype observed in Brca1Δ11/ Δ11 mice without significantly increasing the rates of tumorgenesis
(A) Appearance of mice at one month of age demonstrating that Brca1Δ11/ Δ1153BP1-/- animals appear virtually indistinguishable from WT mice (left panel). By 7 months, Brca1Δ11/ Δ11p53+/- mice develop changes associated with accelerated aging (middle panel) while Brca1Δ11/ Δ1153BP1-/- continue to appear similar to WT animals (right panel). (B) Representative SA-βgal staining in the brain of seven month old animals demonstrating increased tissue senescence in the Brca1Δ11/ Δ11p53+/- animals. Quantification (mean +/- SD) of senescent cells per random high power field (HPF) is shown for WT (black bar), Brca1Δ11/ Δ11p53+/- mice (red bar) and Brca1Δ11/ Δ1153BP1-/- animals (open bar). (C) Representative TUNEL staining in the intestine of 7 month old mice. (D) Sections of skin at 7 months demonstrating age-related changes in the Brca1Δ11/ Δ11p53+/- mice including reduced skin thickness and loss of subcutaneous adiposity. (E) Overall survival of mice with the indicated genotypes demonstrating that in comparison to Brca1Δ11/ Δ11 mice rescued by deletion of one allele of p53, 53BP1 deletion extends lifespan. (F) Rates of tumor free survival demonstrating that a high percentage of Brca1Δ11/ Δ11p53+/- mice develop cancer while this is largely absent in the Brca1Δ11/ Δ1153BP1-/- animals. The number of mice per cohort for this analysis were WT (n=25), 53BP1-/- (n=30), Brca1Δ11/ Δ1153BP1-/- (n=35) and Brca1Δ11/ Δ11p53+/- (n=21).
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References

    1. Adams MM, Carpenter PB. Tying the loose ends together in DNA double strand break repair with 53BP1. Cell Div. 2006;1:19. - PMC - PubMed
    1. Bachelier R, Xu X, Wang X, Li W, Naramura M, Gu H, Deng CX. Normal lymphocyte development and thymic lymphoma formation in Brca1 exon-11-deficient mice. Oncogene. 2003;22:528–537. - PubMed
    1. Barlow C, Hirotsune S, Paylor R, Liyanage M, Eckhaus M, Collins F, Shiloh Y, Crawley JN, Ried T, Tagle D, Wynshaw-Boris A. Atm-deficient mice: a paradigm of ataxia telangiectasia. Cell. 1996;86:159–171. - PubMed
    1. Bartkova J, Horejsi Z, Koed K, Kramer A, Tort F, Zieger K, Guldberg P, Sehested M, Nesland JM, Lukas C, et al. DNA damage response as a candidate anti-cancer barrier in early human tumorigenesis. Nature. 2005;434:864–870. - PubMed
    1. Bartkova J, Rezaei N, Liontos M, Karakaidos P, Kletsas D, Issaeva N, Vassiliou LV, Kolettas E, Niforou K, Zoumpourlis VC, et al. Oncogene-induced senescence is part of the tumorigenesis barrier imposed by DNA damage checkpoints. Nature. 2006;444:633–637. - PubMed

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