53BP1 promotes ATM activity through direct interactions with the MRN complex.

The Mre11/Rad50/Nbs1 (MRN) complex has a central function in facilitating activation of the ATM protein kinase at sites of DNA double-strand breaks (DSBs). However, several other factors are also required in human cells for efficient signalling through MRN and ATM, including the tumour suppressor proteins p53-binding protein 1 (53BP1) and ...
BRCA1. In this study, we investigate the functions of these mediator proteins in ATM activation and find that the presence of 53BP1 and BRCA1 can amplify the effects of MRN when interactions between MRN and ATM are compromised. This effect is dependent on a direct interaction between MRN and the tandem breast cancer carboxy-terminal (BRCT) repeats in 53BP1, and is accompanied by hyper-phosphorylation of both Nbs1 and 53BP1. We also find that the BRCT domains of 53BP1 affect the overall structure of 53BP1 multimers and that this structure is important for promoting ATM phosphorylation of substrates as well as for the repair of DNA DSBs in mammalian cells.
Mesh Terms:
Animals, Ataxia Telangiectasia Mutated Proteins, BRCA1 Protein, Cell Cycle Proteins, Cells, Cultured, DNA Repair Enzymes, DNA-Binding Proteins, Enzyme Activation, Humans, Intracellular Signaling Peptides and Proteins, MRE11 Homologue Protein, Mice, Multiprotein Complexes, Nuclear Proteins, Phosphorylation, Protein Binding, Protein Multimerization, Protein Structure, Tertiary, Protein-Serine-Threonine Kinases, Recombinant Fusion Proteins, Tumor Suppressor Proteins, Tumor Suppressor p53-Binding Protein 1
EMBO J.
Date: Feb. 03, 2010
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