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BRCA2 acts as a RAD51 loader to facilitate telomere replication and capping

Nature Structural & Molecular Biology volume 17, pages 1461–1469 (2010)Cite this article

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Abstract

The tumor suppressor protein BRCA2 is a key component of the homologous recombination pathway of DNA repair, acting as the loader of RAD51 recombinase at sites of double-strand breaks. Here we show that BRCA2 associates with telomeres during the S and G2 phases of the cell cycle and facilitates the loading of RAD51 onto telomeres. Conditional deletion of Brca2 and inhibition of Rad51 in mouse embryonic fibroblasts (MEFs), but not inactivation of Brca1, led to shortening of telomeres and accumulation of fragmented telomeric signals—a hallmark of telomere fragility that is associated with replication defects. These findings suggest that BRCA2-mediated homologous recombination reactions contribute to the maintenance of telomere length by facilitating telomere replication and imply that BRCA2 has an essential role in maintaining telomere integrity during unchallenged cell proliferation. Mouse mammary tumors that lacked Brca2 accumulated telomere dysfunction–induced foci. Human breast tumors in which BRCA2 was mutated had shorter telomeres than those in which BRCA1 was mutated, suggesting that the genomic instability in BRCA2-deficient tumors was due in part to telomere dysfunction.

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Figure 1: BRCA2 is required to recruit RAD51 to the telomeres during the S and G2 phases.
Figure 2: Conditional deletion of Brca2 causes telomere shortening.
Figure 3: BRCA2 and RAD51 are required for maintenance of telomere length in MEFs.
Figure 4: Increased telomere fragility in BRCA2- and RAD51-deficient MEFs.
Figure 5: Homologous recombination activities and the telomeric factor TRF1 act independently in facilitating telomere replication.
Figure 6: Telomere dysfunction–induced foci (TIFs) accumulate in BRCA2- and RAD51-deficient MEFs and in Brca2-deficient mammary tumors.
Figure 7: The function of BRCA2, but not that of BRCA1, is essential for telomere maintenance in human breast tumors.

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Acknowledgements

We thank P. Biggs for generating the targeting construct for the Brca2sko allele, I. Roswell (Cancer Research UK, Clare Hall Laboratories) for help with establishing Trp53−/− MEFs and F. Uhlmann for reading and comments on the manuscript. Work in M. Tarsounas's laboratory is supported by Cancer Research UK and Breast Cancer Campaign. Travel related to this project was funded by a Joint International Award to M. Tarsounas and M.A.B. from The Royal Society. Work in J.J.'s laboratory is supported by the Dutch Cancer Society (KWF) and the Netherlands Organisation for Scientific Research (NWO). M.A.B.'s laboratory was funded by the Spanish Ministry of Innovation and Science. U.H. was supported by the New Jersey Commission on Cancer Research (NJCCR) grant no. 09-1124-CCR-EO.

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Author notes

  1. Sophie Badie, Jose M Escandell and Peter Bouwman: These authors contributed equally to this work.

Authors and Affiliations

  1. Telomere and Genome Stability Group, The Cancer Research UK/Medical Research Council Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, UK

    Sophie Badie, Jose M Escandell, Ana Rita Carlos, Maria Thanasoula & Madalena Tarsounas

  2. Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands

    Peter Bouwman & Jos Jonkers

  3. Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Center (CNIO), Madrid, Spain

    Maria M Gallardo, Isabel Jaco & Maria A Blasco

  4. Department of Microbiology and Molecular Genetics and New Jersey Medical School–University Hospital Cancer Center, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, USA

    Anitha Suram & Utz Herbig

  5. Human Cancer Genetics Program, CNIO, Madrid, Spain

    Javier Benitez

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  1. Sophie Badie
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Contributions

M. Tarsounas, S.B. and J.M.E. designed and planned the experiments. S.B. and J.M.E. performed most of the experiments. P.B. and J.J. generated the Brca2sko conditional mouse model, established immortalized MEFs and contributed to the results in Figure 2a. A.R.C. contributed the results in Figure 1a,b and Supplementary Figure 6a. M. Thanasoula performed the IF-FISH experiments in Figure 6a–c, Supplementary Figure 1d and Supplementary Figure 6b,c. M.M.G., J.B. and M.A.B. performed the experiments in Figure 7b,c. A.S. and U.H. contributed to the results in Figure 6d–f. I.J. designed and validated the shRNA against mouse RAD51. M. Tarsounas made the figures and wrote the paper.

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Correspondence to Madalena Tarsounas.

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Badie, S., Escandell, J., Bouwman, P. et al. BRCA2 acts as a RAD51 loader to facilitate telomere replication and capping. Nat Struct Mol Biol 17, 1461–1469 (2010). https://doi.org/10.1038/nsmb.1943

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