Journal Article

Shieldin complex promotes DNA end-joining and counters homologous recombination in BRCA1-null cells

Jacobs, Jacqueline J. L., Serra, Violeta, Deriano, Ludovic, Lam, Jonathan, Bruna, Alejandra, Demir, Mukerrem, Jackson, Stephen P., Galanty, Yaron, Yang, Fengtang, Belotserkovskaya, Rimma, Fu, Beiyuan, Caldas, Carlos, Shea, Abigail, Coates, Julia, Lescale, Chloe, O’Connor, Mark J., Wu, Qian, Martin, Alistair G., Pellegrini, Luca, Sczaniecka-Clift, Matylda, Pilger, Domenic, Beli, Petra, Lai, Zhongwu, Balmus, Gabriel, Chiang, Ting-Wei Will, Herzog, Mareike, Ostermaier, Matthias, Wei, Wenming, Dev, Harveer, de Krijger, Inge

2018

Overview

BRCA1 deficiencies cause breast, ovarian, prostate and other cancers, and render tumours hypersensitive to poly(ADP-ribose) polymerase (PARP) inhibitors. To understand the resistance mechanisms, we conducted whole-genome CRISPR–Cas9 synthetic-viability/resistance screens in BRCA1-deficient breast cancer cells treated with PARP inhibitors. We identified two previously uncharacterized proteins, C20orf196 and FAM35A, whose inactivation confers strong PARP-inhibitor resistance. Mechanistically, we show that C20orf196 and FAM35A form a complex, ‘Shieldin’ (SHLD1/2), with FAM35A interacting with single-stranded DNA through its C-terminal oligonucleotide/oligosaccharide-binding fold region. We establish that Shieldin acts as the downstream effector of 53BP1/RIF1/MAD2L2 to promote DNA double-strand break (DSB) end-joining by restricting DSB resection and to counteract homologous recombination by antagonizing BRCA2/RAD51 loading in BRCA1-deficient cells. Notably, Shieldin inactivation further sensitizes BRCA1-deficient cells to cisplatin, suggesting how defining the SHLD1/2 status of BRCA1-deficient tumours might aid patient stratification and yield new treatment opportunities. Highlighting this potential, we document reduced SHLD1/2 expression in human breast cancers displaying intrinsic or acquired PARP-inhibitor resistance. Through CRISPR–Cas9 screen, Dev et al. identified that SHLD1/2 inhibition contributes to PARP-inhibitor resistance. Mechanistically, SHLDs promote non-homologous end-joining and antagonize homologous recombination.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 101/58 / 14/63 / 45/15 / 631/337/1427 / 631/67 / 64/60 / Adenosine diphosphate / Animals / B cells / Biochemistry, Molecular Biology / Biomedical and Life Sciences / Biotechnology / Bone Neoplasms - drug therapy / Bone Neoplasms - genetics / Bone Neoplasms - metabolism / Bone Neoplasms - pathology / BRCA1 protein / BRCA1 Protein - deficiency / BRCA1 Protein - genetics / BRCA2 protein / Breast cancer / Breast Neoplasms - drug therapy / Breast Neoplasms - genetics / Breast Neoplasms - metabolism / Breast Neoplasms - pathology / Cancer / Cancer cells / Cancer genetics / Cancer Research / Care and treatment / Cell Biology / Cell Cycle Proteins / Cell Line, Tumor / Cellular Biology / Cisplatin / Cisplatin - pharmacology / CRISPR / Deactivation / Deoxyribonucleic acid / Developmental Biology / DNA / DNA Breaks, Double-Stranded / DNA damage / DNA End-Joining Repair / DNA-Binding Proteins / Dose-Response Relationship, Drug / Double-strand break repair / Drug Resistance, Neoplasm - genetics / Female / Gene expression / Genetic aspects / Genetics / Genomes / Genomics / HEK293 Cells / Homologous recombination / Homology / Humans / Inactivation / Inhibitors / Ionizing radiation / Life Sciences / Mad2 Proteins - genetics / Mad2 Proteins - metabolism / Mice / Molecular biology / Monosaccharides / Multiprotein Complexes / Null cells / Oligonucleotides / Oligosaccharides / Osteosarcoma - drug therapy / Osteosarcoma - genetics / Osteosarcoma - metabolism / Osteosarcoma - pathology / Ovarian Neoplasms - drug therapy / Ovarian Neoplasms - genetics / Ovarian Neoplasms - metabolism / Ovarian Neoplasms - pathology / Poly(ADP-ribose) / Poly(ADP-ribose) polymerase / Poly(ADP-ribose) Polymerase Inhibitors - pharmacology / Prostate / Proteins / Proteins - genetics / Proteins - metabolism / Recombinational DNA Repair / Ribose / Screens / Single-stranded DNA / Stem Cells / Surgery / Telomere-Binding Proteins - genetics / Telomere-Binding Proteins - metabolism / Tumor Suppressor p53-Binding Protein 1 - genetics / Tumor Suppressor p53-Binding Protein 1 - metabolism / Tumors / Viability / Xenograft Model Antitumor Assays