Apurinic/Apyrimidinic Endonuclease 1 Is the Essential Nuclease during Immunoglobulin Class Switch Recombination
Apurinic/Apyrimidinic Endonuclease 1 Is the Essential Nuclease during Immunoglobulin Class Switch Recombination
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DOI：
10.1128/mcb.00026-13
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发表时间：
2013-04-01
影响因子：
5.3
通讯作者：
Yu, Kefei
中科院分区：
文献类型：
--
作者：
Masani, Shahnaz;Han, Li;Yu, Kefei
免疫球蛋白（IG）类别转换重组（CSR）由激活诱导的胞苷脱氨酶（AID）启动，所述AID催化转换区域内的大量DNA胞嘧啶脱氨基。产生的尿嘧啶被尿嘧啶碱基切除和/或错配修复酶加工，最终产生开关区DNA双链断裂（DSB）。尿嘧啶糖基化酶2（UNG 2）是CSR所必需的，最有可能通过去除尿嘧啶产生脱碱基位点。尽管推测脱嘌呤/脱嘧啶核酸内切酶1（APE 1）在这些脱碱基位点产生DNA链切口（CSR的先决条件），但由于APE 1消融在小鼠中的胚胎致死性，因此难以直接测试CSR中对APE 1的需求。在这里，我们报告的成功删除APE 1基因在小鼠B细胞系（CH 12 F3）能够在体外强大的CSR。与APE 1对细胞活力至关重要的一般假设相反，CH 12 F3细胞中APE 1的缺失对细胞活力或生长没有明显影响。此外，无APE 1的CH12F3细胞中的CSR显著降低，为APE 1在开关区切割和CSR中的重要作用提供了直接证据。最后，AP核酸内切酶2（APE2）的缺失对APE1-熟练或缺乏细胞中的CSR没有影响。
Immunoglobulin (Ig) class switch recombination (CSR) is initiated by activation-induced cytidine deaminase (AID) that catalyzes numerous DNA cytosine deaminations within switch regions. The resulting uracils are processed by uracil base excision and/or mismatch repair enzymes that ultimately generate switch region DNA double-strand breaks (DSBs). Uracil glycosylase 2 (UNG2) is required for CSR, most likely by removing uracils to generate abasic sites. Although it is presumed that the apurinic/apyrimidinic endonuclease 1 (APE1) generates DNA strand incisions (a prerequisite for CSR) at these abasic sites, a direct test of the requirement for APE1 in CSR has been difficult because of the embryonic lethality of APE1 ablation in mice. Here, we report the successful deletion of the APE1 gene in a mouse B cell line (CH12F3) capable of robust CSR in vitro. In contrast to the general assumption that APE1 is essential for cellular viability, deletion of APE1 in CH12F3 cells has no apparent effect on cell viability or growth. Moreover, CSR in APE1-null CH12F3 cells is drastically reduced, providing direct evidence for an essential role for APE1 in switch region cleavage and CSR. Finally, deletion of AP endonuclease 2 (APE2) has no effect on CSR in either APE1-proficient or -deficient cells.