Apurinic/apyrimidinic endonuclease 1 (APE1) is dispensable for activation-induced cytidine deaminase (AID)-dependent somatic hypermutation in the immunoglobulin gene.
Apurinic/apyrimidinic endonuclease 1 (APE1) is dispensable for activation-induced cytidine deaminase (AID)-dependent somatic hypermutation in the immunoglobulin gene.
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无嘌呤/无嘧啶核酸内切酶 1 (APE1) 对于免疫球蛋白基因中激活诱导的胞苷脱氨酶 (AID) 依赖性体细胞超突变来说是可有可无的。
DOI：
10.1093/intimm/dxz028
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发表时间：
2019
影响因子：
4.4
通讯作者：
Maki Kobayashi and Tasuku Honjo.
中科院分区：
文献类型：
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作者：
Helena Islam;Maki Kobayashi and Tasuku Honjo.
激活诱导的胞苷脱氨酶 (AID) 会引发免疫球蛋白基因可变 (V) 和开关 (S) 区域的 DNA 断裂，从而分别导致体细胞超突变 (SHM) 和类别开关重组 (CSR)。无嘌呤/无嘧啶核酸内切酶 1 (APE1) 已被证明对 CSR 很重要，并且当 AID 依赖性脱氨基胞苷被尿嘧啶 DNA 糖基化酶去除时，应该在脱碱基位点进行切割。然而，出人意料的是，APE1 对于小鼠 B 淋巴瘤细胞系 CH12F3-2A 中 S 区的 SHM 以及免疫球蛋白重链 (IgH) 和 c-myc 基因之间的易位来说是可有可无的。这表明 APE1 不参与 AID 依赖性 DNA 断裂，而是参与 DNA 修复。为了研究 APE1 参与 CSR 和 SHM 的详细分子机制，我们通过醛反应探针标记测量了无嘌呤/无嘧啶 (AP) 位点。结果表明，APE1−/−/−CH12F3-2A 和野生型 CH12F3-2A 细胞之间 S 区 AP 位点的频率没有差异。为了在 V 区的 SHM 中进行类似的实验，我们生成了 APE1 敲除 (APE1−/−) 人伯基特淋巴瘤细胞系，并比较了 APE1 丰富和缺陷的 BL2 淋巴瘤细胞之间的 SHM。 APE1−/−BL2 和 APE1 熟练细胞 V 区的 SHM 频率也相似。综上所述，我们发现 AID 不会诱导 IgH 基因 S 区中的 AP 位点，并且 APE1 对于 V 区和 S 区中的 SHM 来说不是必需的；然而，在 CSR 中 DNA 断裂后需要进行 DNA 修复。
Activation-induced cytidine deaminase (AID) initiates DNA breakage in the variable (V) and switch (S) regions of the immunoglobulin gene, which results in somatic hypermutation (SHM) and class switch recombination (CSR), respectively. Apurinic/apyrimidinic endonuclease 1 (APE1) has been shown to be important for CSR, and is supposed to cleave at abasic sites when AID-dependently deaminated cytidine is removed by uracil DNA glycosylase. However, APE1 is unexpectedly dispensable for SHM in the S region and translocation between immunoglobulin heavy chain (IgH) and c-myc genes in the mouse B lymphoma cell line, CH12F3-2A. This suggested that APE1 is not involved in AID-dependent DNA breakage, but rather, in DNA repair. In order to investigate detailed molecular mechanisms underlying APE1’s involvement in CSR and SHM, we measured apurinic/apyrimidinic (AP) sites via aldehyde reactive probe labeling. Results indicated that the frequencies of AP sites in the S regions were not different between APE1−/−/−CH12F3-2A and wild-type CH12F3-2A cells. To carry out similar experiments in SHM of the V region, we generated an APE1 knockout (APE1−/−) human Burkitt’s lymphoma cell line, and compared SHM between APE1-proficient and -deficient BL2 lymphoma cells. SHM frequencies in the V regions of APE1−/−BL2 and APE1-proficient cells were also similar. Taken together, we showed that AID does not induce AP sites in the S region of the IgH gene, and that APE1 is not necessary for SHM in the V and S regions; however, it is required for DNA repair following DNA breakage in CSR.