Involvement of Artemis in nonhomologous end-joining during immunoglobulin class switch recombination
Involvement of Artemis in nonhomologous end-joining during immunoglobulin class switch recombination
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DOI：
10.1084/jem.20081915
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发表时间：
2008-12-22
影响因子：
15.3
通讯作者：
Pan-Hammarstrom, Qiang
中科院分区：
文献类型：
--
作者：
Du, Likun;van der Burg, Mirjam;Pan-Hammarstrom, Qiang
在开关(S)区域引入的DNA双链断裂是免疫球蛋白类开关重组(CSR)的中间产物。这些断裂随后被识别、处理和连接，导致两个S区域的重组。非同源末端连接(NHEJ)被认为是CSR过程中DSB修复的主要机制。然而，NHEJ中的一个重要组成部分Artemis被认为是有效的CSR所必需的。在这项研究中，我们表征了来自Artemis缺陷型人B细胞的S重组连接。S-Sα连接基因可以从所有被检测的患者中扩增，其特征是完全缺乏直接的末端连接，并且显著改变了使用替代的、基于微同源的末端连接途径。S-S伽玛连接只能从一名携带“亚型”突变的患者身上扩增出来。虽然这些S-S伽马连接看起来是正常的，但观察到一种不寻常的从免疫球蛋白(Ig)M通过一个免疫球蛋白亚类到不同的免疫球蛋白亚类的顺序切换显著增加，S-S伽马连接显示出很长的微同源性。因此，当Artemis的功能受损时，不同的S地区可以使用不同的CSR连接分辨率模式。我们的发现强烈地将Artemis与CSR期间主要的NHEJ途径联系在一起。
DNA double-strand breaks (DSBs) introduced in the switch (S) regions are intermediates during immunoglobulin class switch recombination (CSR). These breaks are subsequently recognized, processed, and joined, leading to recombination of the two S regions. Nonhomologous end-joining (NHEJ) is believed to be the principle mechanism involved in DSB repair during CSR. One important component in NHEJ, Artemis, has however been considered to be dispensable for efficient CSR. In this study, we have characterized the S recombinational junctions from Artemis-deficient human B cells. S mu-S alpha junctions could be amplified from all patients tested and were characterized by a complete lack of "direct" end-joining and a remarkable shift in the use of an alternative, microhomology-based end-joining pathway. S mu-S gamma junctions could only be amplified from one patient who carries "hypomorphic" mutations. Although these S mu-S gamma junctions appear to be normal, a significant increase of an unusual type of sequential switching from immunoglobulin (Ig)M, through one IgG subclass, to a different IgG subclass was observed, and the S gamma-S gamma junctions showed long microhomologies. Thus, when the function of Artemis is impaired, varying modes of CSR junction resolution may be used for different S regions. Our findings strongly link Artemis to the predominant NHEJ pathway during CSR.