Lamin A/C promotes DNA base excision repair (human arrays). Lamin A/C promotes DNA base excision repair (human arrays)

The A-type lamins (lamin A/C), encoded by the Lmna gene, are important structural components of the nuclear lamina. Lmna mutations lead to degenerative disorders, including the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). In addition, altered lamin A/C expression is found in various cancers. Reports indicate that lamin A/C plays a role in DNA double strand break repair, but a role in DNA base excision repair (BER) has not been described. We provide evidence for reduced BER efficiency in lamin A/C-depleted cells. The mechanism involves impairment of the APE1 and POLβ enzyme activities in BER. Also, Lmna null mouse fibroblasts displayed reduced expression of several core BER enzymes (PARP1, LIG3, and POLβ). Moreover, the robustness of APE1 and POLβ activities and the rate of BER were enhanced by lamin A/C-augmented poly(ADP-ribose) polymer formation (PARylation). Finally, we report that HGPS fibroblasts are defective in BER. Collectively, our results provide novel insights into the functional interplay between the nuclear lamina and cellular defenses against oxidative DNA damage, with implications for human cancer and aging. Overall design: Microarray analysis of cell lines from Hutchinson-Gilford progeria syndrome (HGPS)-affected individuals and a clinically unaffected parent (three patient-parent pairs, three replicates per condition) for a total of eighteen microarray samples.

由Lmna基因编码的A型核纤层蛋白（lamin A/C）是核纤层的重要结构组成成分。Lmna基因突变可引发多种退行性疾病，包括早老性疾病哈钦森-吉尔福德早老综合征（Hutchinson-Gilford progeria syndrome, HGPS）。此外，多种癌症中均存在核纤层蛋白A/C表达异常的情况。已有研究显示，核纤层蛋白A/C参与DNA双链断裂修复（DNA double strand break repair），但尚未见其在DNA碱基切除修复（base excision repair, BER）中发挥功能的相关报道。
本研究证实，核纤层蛋白A/C敲低的细胞其碱基切除修复效率显著降低，其分子机制涉及BER通路中AP核酸内切酶1（APE1）与DNA聚合酶β（POLβ）的酶活性受损。同时，Lmna基因敲除的小鼠成纤维细胞中，多种核心BER通路酶——聚ADP核糖聚合酶1（PARP1）、DNA连接酶3（LIG3）及DNA聚合酶β（POLβ）的表达水平均出现下调。此外，核纤层蛋白A/C可通过增强多聚ADP核糖基化（poly(ADP-ribose) polymer formation, PARylation）过程，提升APE1与POLβ的酶活性以及BER通路的反应速率。最后，本研究发现哈钦森-吉尔福德早老综合征患者的成纤维细胞存在碱基切除修复缺陷。
综上，本研究结果为核纤层与细胞抗氧化DNA损伤防御机制之间的功能互作提供了全新见解，该发现对人类癌症与衰老研究具有潜在参考价值。
本研究的整体实验设计为：对哈钦森-吉尔福德早老综合征（HGPS）患者及其临床健康双亲的细胞系（共3组患者-亲代配对样本，每组设置3次生物学重复）进行微阵列分析，总计获得18份微阵列样本。