53BP1 cooperation with the REV7-shieldin complex underpins DNA structure-specific NHEJ.
Ghezraoui HGenome Integrity Laboratory, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
Oliveira CGenome Integrity Laboratory, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
Becker JRGenome Integrity Laboratory, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
Bilham KGenome Integrity Laboratory, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
Moralli DChromosome Dynamics, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
Anzilotti CMRC Human Immunology Unit, Weatherall Institute for Molecular Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
Fischer RTarget Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
Deobagkar-Lele MMRC Human Immunology Unit, Weatherall Institute for Molecular Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
Sanchiz-Calvo MGenome Integrity Laboratory, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
Fueyo-Marcos EGenome Integrity Laboratory, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
Bonham STarget Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
Kessler BMTarget Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
Rottenberg SInstitute of Animal Pathology, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
Cornall RJMRC Human Immunology Unit, Weatherall Institute for Molecular Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
Green CMChromosome Dynamics, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
Chapman JRGenome Integrity Laboratory, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK. rchapman@well.ox.ac.uk.
English
53BP1 governs a specialized, context-specific branch of the classical non-homologous end joining DNA double-strand break repair pathway. Mice lacking 53bp1 (also known as Trp53bp1) are immunodeficient owing to a complete loss of immunoglobulin class-switch recombination1,2, and reduced fidelity of long-range V(D)J recombination3. The 53BP1-dependent pathway is also responsible for pathological joining events at dysfunctional telomeres4, and its unrestricted activity in Brca1-deficient cellular and tumour models causes genomic instability and oncogenesis5-7. Cells that lack core non-homologous end joining proteins are profoundly radiosensitive8, unlike 53BP1-deficient cells9,10, which suggests that 53BP1 and its co-factors act on specific DNA substrates. Here we show that 53BP1 cooperates with its downstream effector protein REV7 to promote non-homologous end joining during class-switch recombination, but REV7 is not required for 53BP1-dependent V(D)J recombination. We identify shieldin-a four-subunit putative single-stranded DNA-binding complex comprising REV7, c20orf196 (SHLD1), FAM35A (SHLD2) and FLJ26957 (SHLD3)-as the factor that explains this specificity. Shieldin is essential for REV7-dependent DNA end-protection and non-homologous end joining during class-switch recombination, and supports toxic non-homologous end joining in Brca1-deficient cells, yet is dispensable for REV7-dependent interstrand cross-link repair. The 53BP1 pathway therefore comprises distinct double-strand break repair activities within chromatin and single-stranded DNA compartments, which explains both the immunological differences between 53bp1- and Rev7- deficient mice and the context specificity of the pathway.