Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, NY 10029, USA.
Cell Rep. 2012 Dec 27;2(6):1505-12. doi: 10.1016/j.celrep.2012.11.004. Epub 2012 Dec 7.
DNA ligase IV (LigIV) and Artemis are central components of the nonhomologous end-joining (NHEJ) machinery that is required for V(D)J recombination and the maintenance of genomic integrity in mammalian cells. We report here crystal structures of the LigIV DNA binding domain (DBD) in both its apo form and in complex with a peptide derived from the Artemis C-terminal region. We show that LigIV interacts with Artemis through an extended hydrophobic surface. In particular, we find that the helix α2 in LigIV-DBD is longer than in other mammalian ligases and presents residues that specifically interact with the Artemis peptide, which adopts a partially helical conformation on binding. Mutations of key residues on the LigIV-DBD hydrophobic surface abolish the interaction. Together, our results provide structural insights into the specificity of the LigIV-Artemis interaction and how the enzymatic activities of the two proteins may be coordinated during NHEJ.
DNA 连接酶 IV（LigIV）和 Artemis 是非同源末端连接（NHEJ）机制的核心组成部分，该机制是哺乳动物细胞中 V(D)J 重组和维持基因组完整性所必需的。我们在此报告 LigIV 的 DNA 结合结构域（DBD）的晶体结构，包括其无配体形式和与来自 Artemis C 末端区域的肽的复合物形式。我们表明，LigIV 通过扩展的疏水表面与 Artemis 相互作用。特别是，我们发现 LigIV-DBD 中的α2 螺旋比其他哺乳动物连接酶长，并呈现出与 Artemis 肽特异性相互作用的残基，该肽在结合时呈现部分螺旋构象。LigIV-DBD 疏水表面上关键残基的突变会破坏相互作用。总之，我们的结果提供了对 LigIV-Artemis 相互作用特异性的结构见解，以及在 NHEJ 过程中这两种蛋白质的酶活性如何协调。
