Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10065, USA.
J Exp Med. 2013 Jan 14;210(1):115-23. doi: 10.1084/jem.20121975. Epub 2012 Dec 17.
DNA double-strand breaks (DSBs) are byproducts of normal cellular metabolism and obligate intermediates in antigen receptor diversification reactions. These lesions are potentially dangerous because they can lead to deletion of genetic material or chromosome translocation. The chromatin-binding protein 53BP1 and the histone variant H2AX are required for efficient class switch (CSR) and V(D)J recombination in part because they protect DNA ends from resection and thereby favor nonhomologous end joining (NHEJ). Here, we examine the mechanism of DNA end resection in primary B cells. We find that resection depends on both CtBP-interacting protein (CtIP, Rbbp8) and exonuclease 1 (Exo1). Inhibition of CtIP partially rescues the CSR defect in 53BP1- and H2AX-deficient lymphocytes, as does interference with the RecQ helicases Bloom (Blm) and Werner (Wrn). We conclude that CtIP, Exo1, and RecQ helicases contribute to the metabolism of DNA ends during DSB repair in B lymphocytes and that minimizing resection favors efficient CSR.
DNA 双链断裂 (DSBs) 是正常细胞代谢的副产物，也是抗原受体多样化反应的必需中间产物。这些损伤是潜在危险的，因为它们可能导致遗传物质的缺失或染色体易位。染色质结合蛋白 53BP1 和组蛋白变体 H2AX 是有效类别转换 (CSR) 和 V(D)J 重组所必需的，部分原因是它们保护 DNA 末端免受切除，从而有利于非同源末端连接 (NHEJ)。在这里，我们研究了初级 B 细胞中 DNA 末端切除的机制。我们发现，切除依赖于 CtBP 相互作用蛋白 (CtIP，Rbbp8) 和核酸外切酶 1 (Exo1)。CtIP 的抑制部分挽救了 53BP1 和 H2AX 缺陷淋巴细胞中的 CSR 缺陷，Bloom (Blm) 和 Werner (Wrn) 等 RecQ 解旋酶的干扰也是如此。我们得出结论，CtIP、Exo1 和 RecQ 解旋酶有助于 B 淋巴细胞中 DSB 修复过程中 DNA 末端的代谢，并且最小化切除有利于有效的 CSR。
