Nedd4 Family Interacting Protein 1 (Ndfip1) Is Required for Ubiquitination and Nuclear Trafficking of BRCA1-associated ATM Activator 1 (BRAT1) during the DNA Damage Response

• Published in: The Journal of biological chemistry Vol. 290; no. 11; pp. 7141 - 7150
• Main Authors: Low, Ley-Hian, Chow, Yuh-Lit, Li, Yijia, Goh, Choo-Peng, Putz, Ulrich, Silke, John, Ouchi, Toru, Howitt, Jason, Tan, Seong-Seng
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 13.03.2015; American Society for Biochemistry and Molecular Biology
• Subjects: Active Transport, Cell Nucleus; Animals; Ataxia Telangiectasia Mutated Proteins - metabolism; Brain Injuries - metabolism; Carrier Proteins - metabolism; Cell Line; DNA Damage; DNA Damage Response; Endosomal Sorting Complexes Required for Transport - metabolism; HEK293 Cells; Humans; Intercellular Signaling Peptides and Proteins; Intracellular Trafficking; Membrane Proteins - metabolism; Mice, Inbred C57BL; Molecular Bases of Disease; Nedd4 Ubiquitin Protein Ligases; Neuroprotection; Nuclear Proteins - metabolism; Nuclear Transport; Protein Binding; Protein Interaction Mapping; Protein Interaction Maps; Proteolysis; Signal Transduction; Ubiquitin-Protein Ligases - metabolism; Ubiquitination; Ubiquitylation (ubiquitination); DNA Damage Response; Neuroprotection; Intracellular Trafficking; Nuclear Transport; Ubiquitylation (ubiquitination)
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.613687

During injury, cells are vulnerable to apoptosis from a variety of stress conditions including DNA damage causing double-stranded breaks. Without repair, these breaks lead to aberrations in DNA replication and transcription, leading to apoptosis. A major response to DNA damage is provided by the protein kinase ATM (ataxia telangiectasia mutated) that is capable of commanding a plethora of signaling networks for DNA repair, cell cycle arrest, and even apoptosis. A key element in the DNA damage response is the mobilization of activating proteins into the cell nucleus to repair damaged DNA. BRAT1 is one of these proteins, and it functions as an activator of ATM by maintaining its phosphorylated status while also keeping other phosphatases at bay. However, it is unknown how BRAT1 is trafficked into the cell nucleus to maintain ATM phosphorylation. Here we demonstrate that Ndfip1-mediated ubiquitination of BRAT1 leads to BRAT1 trafficking into the cell nucleus. Without Ndfip1, BRAT1 failed to translocate to the nucleus. Under genotoxic stress, cells showed increased expression of both Ndfip1 and phosphorylated ATM. Following brain injury, neurons show increased expression of Ndfip1 and nuclear translocation of BRAT1. These results point to Ndfip1 as a sensor protein during cell injury and Ndfip1 up-regulation as a cue for BRAT1 ubiquitination by Nedd4 E3 ligases, followed by nuclear translocation of BRAT1. Background: The function of Ndfip1 in DNA repair is unknown. Results: Ndfip1 is required during stress for ubiquitinating and trafficking BRAT1 into the nucleus. Conclusion: Ndfip1 is required for activating the ATM (ataxia telangiectasia mutated) pathway for DNA repair during stress injury. Significance: We describe a new mechanism for ubiquitinating and trafficking of BRAT1 into the nucleus for DNA repair.