Department of Pathology, New York University School of Medicine, New York, NY 10016, USA.
Cell Rep. 2013 Sep 12;4(5):870-8. doi: 10.1016/j.celrep.2013.07.041. Epub 2013 Aug 29.
V(D)J recombination-associated DNA double-strand breaks (DSBs) are normally repaired by the high-fidelity classical nonhomologous end-joining (cNHEJ) machinery. Previous studies implicated the recombination-activating gene (RAG)/DNA postcleavage complex (PCC) in regulating pathway choice by preventing access to inappropriate repair mechanisms such as homologous recombination (HR) and alternative NHEJ (aNHEJ). Here, we report that RAG2's "acidic hinge," previously of unknown function, is critical for several key steps. Mutations that reduce the hinge's negative charge destabilize the PCC, disrupt pathway choice, permit repair of RAG-mediated DSBs by the translocation-prone aNHEJ machinery, and reduce genomic stability in developing lymphocytes. Structural predictions and experimental results support our hypothesis that reduced flexibility of the hinge underlies these outcomes. Furthermore, sequence variants present in the human population reduce the hinge's negative charge, permit aNHEJ, and diminish genomic integrity.
V(D)J 重组相关的 DNA 双链断裂 (DSB) 通常通过高保真的经典非同源末端连接 (cNHEJ) 机制修复。先前的研究表明，重组激活基因 (RAG)/DNA 后切割复合物 (PCC) 通过防止与不合适的修复机制（如同源重组 (HR) 和替代 NHEJ (aNHEJ)）接触，从而调节途径选择。在这里，我们报告说，RAG2 的“酸性铰链”（先前功能未知）对于几个关键步骤至关重要。降低铰链负电荷的突变会破坏 PCC，扰乱途径选择，允许易位倾向的 aNHEJ 机制修复 RAG 介导的 DSB，并降低发育中的淋巴细胞的基因组稳定性。结构预测和实验结果支持了我们的假设，即铰链的柔韧性降低是这些结果的基础。此外，存在于人类群体中的序列变异会降低铰链的负电荷，允许 aNHEJ，并降低基因组完整性。
