Brown Matthew L, Franco Daniel, Burkle Alexander, Chang Yung
Department of Microbiology, Molecular and Cellular Biology Program, Arizona State University, Tempe, AZ 85287-2701, USA.
Proc Natl Acad Sci U S A. 2002 Apr 2;99(7):4532-7. doi: 10.1073/pnas.072495299.
V(D)J recombination is critical to the generation of a functional immune system. Intrinsic to the assembly of antigen receptor genes is the formation of endogenous DNA double-strand breaks, which normally are excluded from the cellular surveillance machinery because of their sequestration in a synaptic complex and/or rapid resolution. In cells deficient in double-strand break repair, such recombination-induced breaks fail to be joined promptly and therefore are at risk of being recognized as DNA damage. Poly(ADP-ribose) polymerase-1 is an important factor in the maintenance of genomic integrity and is believed to play a central role in DNA repair. Here we provide visual evidence that in a recombination inducible severe combined immunodeficient cell line poly(ADP-ribose) formation occurs during the resolution stage of V(D)J recombination where nascent opened coding ends are generated. Poly(ADP-ribose) formation appears to facilitate coding end resolution. Furthermore, formation of Mre11 foci coincide with these areas of poly(ADP-ribosyl)ation. In contrast, such a response is not observed in wild-type cells possessing a functional catalytic subunit of DNA-dependent protein kinase (DNA-PK(cs)). Thus, V(D)J recombination invokes a DNA damage response in cells lacking DNA-PK(cs) activity, which in turn promotes DNA-PK(cs)-independent resolution of recombination intermediates.
V(D)J重组对于功能性免疫系统的产生至关重要。抗原受体基因组装的内在过程是内源性DNA双链断裂的形成，由于这些断裂被隔离在突触复合体中或能快速修复，通常会被细胞监测机制排除在外。在双链断裂修复缺陷的细胞中，这种重组诱导的断裂无法迅速连接，因此有被识别为DNA损伤的风险。聚（ADP-核糖）聚合酶-1是维持基因组完整性的重要因素，被认为在DNA修复中起核心作用。在这里，我们提供了可视化证据，表明在重组诱导的严重联合免疫缺陷细胞系中，聚（ADP-核糖）的形成发生在V(D)J重组的分辨率阶段，此时会产生新生的开放编码末端。聚（ADP-核糖）的形成似乎有助于编码末端的分辨率。此外，Mre11焦点的形成与这些聚（ADP-核糖基）化区域一致。相比之下，在具有功能性DNA依赖性蛋白激酶催化亚基（DNA-PK(cs)）的野生型细胞中未观察到这种反应。因此，V(D)J重组在缺乏DNA-PK(cs)活性的细胞中引发了DNA损伤反应，这反过来又促进了重组中间体的DNA-PK(cs)非依赖性分辨率。
