RAG2's Acidic Hinge Restricts Repair-Pathway Choice

Coussens MA, Wendland RL, Deriano L, Lindsay CR, Arnal SM, Roth DB.
Cell Rep. 2013 Sep 12;4(5):870-8. doi: 10.1016/j.celrep.2013.07.041. Epub 2013 Aug 29.

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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, the Roth Lab reports 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.

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