53BP1-dependent robust localized KAP-1 phosphorylation is essential for heterochromatic DNA double-strand break repair

• Published in: Nature cell biology Vol. 12; no. 2; pp. 177 - 184
• Main Authors: Löbrich, Markus, Jeggo, Penelope A, Noon, Angela T, Rief, Nicole, Goodarzi, Aaron A, Shibata, Atsushi, Stewart, Grant S
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-02-2010; Nature Publishing Group
• Subjects: 631/337/1427/2122; 631/80/458/1733; 631/80/86; Animals; Ataxia Telangiectasia Mutated Proteins; Biology; Biomedical and Life Sciences; Cancer Research; Cell Biology; Cell Cycle Proteins - metabolism; Cell Line; Cells, Cultured; Deoxyribonucleic acid; Developmental Biology; DNA; DNA Breaks, Double-Stranded - radiation effects; DNA damage; DNA repair; DNA Repair - genetics; DNA Repair - physiology; DNA Repair Enzymes; DNA-Binding Proteins - metabolism; Fluorescent Antibody Technique; Heterochromatin - metabolism; Heterochromatin - radiation effects; Humans; Immunoblotting; Immunoprecipitation; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - physiology; Ionizing radiation; letter; Life Sciences; Mice; MRE11 Homologue Protein; NIH 3T3 Cells; Nuclear Proteins - metabolism; Phosphorylation; Physiological aspects; Protein-Serine-Threonine Kinases - metabolism; Proteins; Radiation; Radiation, Ionizing; Repressor Proteins - metabolism; Stem Cells; Trans-Activators - metabolism; Transcription factors; Tripartite Motif-Containing Protein 28; Tumor Suppressor p53-Binding Protein 1; Tumor Suppressor Proteins - metabolism; Ubiquitin-Protein Ligases - metabolism; Yeast; United Kingdom; Japan; Germany; United Kingdom > UK
• ISSN: 1465-7392; 1476-4679
• DOI: 10.1038/ncb2017

DNA double-strand breaks (DSBs) trigger ATM (ataxia telangiectasia mutated) signalling and elicit genomic rearrangements and chromosomal fragmentation if misrepaired or unrepaired. Although most DSB repair is ATM-independent, ∼15% of ionizing radiation (IR)-induced breaks persist in the absence of ATM-signalling. 53BP1 (p53-binding protein 1) facilitates ATM-dependent DSB repair but is largely dispensable for ATM activation or checkpoint arrest. ATM promotes DSB repair within heterochromatin by phosphorylating KAP-1 (KRAB-associated protein 1, also known as TIF1β, TRIM28 or KRIP-1; ref. 2). Here, we show that the ATM signalling mediator proteins MDC1, RNF8, RNF168 and 53BP1 are also required for heterochromatic DSB repair. Although KAP-1 phosphorylation is critical for 53BP1-mediated repair, overall phosphorylated KAP-1 (pKAP-1) levels are only modestly affected by 53BP1 loss. pKAP-1 is transiently pan-nuclear but also forms foci overlapping with γH2AX in heterochromatin. Cells that do not form 53BP1 foci, including human RIDDLE (radiosensitivity, immunodeficiency, dysmorphic features and learning difficulties) syndrome cells, fail to form pKAP-1 foci. 53BP1 amplifies Mre11-NBS1 accumulation at late-repairing DSBs, concentrating active ATM and leading to robust, localized pKAP-1. We propose that ionizing-radiation induced foci (IRIF) spatially concentrate ATM activity to promote localized alterations in regions of chromatin otherwise inhibitory to repair.