Involvement of xeroderma pigmentosum group A (XPA) in progeria arising from defective maturation of prelamin A
Involvement of xeroderma pigmentosum group A (XPA) in progeria arising from defective maturation of prelamin A
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DOI：
10.1096/fj.07-8598com
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发表时间：
2008-02-01
期刊：
影响因子：
4.8
通讯作者：
Zou, Yue
中科院分区：
文献类型：
--
作者：
Liu, Yiyong;Wang, Youjie;Zou, Yue
DNA损伤的细胞积累与细胞衰老、衰老和早衰有广泛的关系。在Hutchinson-Gilford早衰综合征（HGPS）和限制性皮肤病（RD）中，过早衰老与DNA双链断裂（DSBs）的积累有关，从而导致基因组不稳定。然而，尽管存在完整的DNA修复蛋白，dsb如何在细胞中积累仍是未知的。在这里，我们报道了DSB修复因子Rad50和Rad51在DSB位点的募集（由γ - h2ax标记）在人类HGPS和zmpste24缺陷细胞中受损。一致地，尽管喜树碱诱导的dsb在类早衰细胞中被有效地去除，但与早衰相关的dsb似乎是不可修复的。我们还发现这些类早衰细胞表现出色素性干皮病A组（XPA）的核病灶，这是一种独特的核苷酸切除修复蛋白。引人注目的是，这些XPA病灶与早老年性细胞中的DSB位点共定位。利用改良的染色质免疫沉淀法和共免疫沉淀法，进一步证实了XPA-DSB关联是由DNA介导的。Western blot分析、免疫荧光和彗星实验证明，RNA干扰（RNAi）敲低XPA在HGPS细胞中部分恢复DSB修复。我们认为，XPA在DSB上或DSB附近的非特征性定位抑制了DSB的修复，从而导致了由前纤层蛋白A成熟过程中的遗传缺陷引起的早衰症的早衰表型。
Cellular accumulation of DNA damage has been widely implicated in cellular senescence, aging, and premature aging. In Hutchinson-Gilford progeria syndrome (HGPS) and restrictive dermopathy (RD), premature aging is linked to accumulation of DNA double-strand breaks (DSBs), which results in genome instability. However, how DSBs accumulate in cells despite the presence of intact DNA repair proteins remains unknown. Here we report that the recruitment of DSB repair factors Rad50 and Rad51 to the DSB sites, as marked by gamma-H2AX, was impaired in human HGPS and Zmpste24-deficient cells. Consistently, the progeria-associated DSBs appeared to be unrepairable although DSBs induced by camptothecin were efficiently removed in the progeroid cells. We also found that these progeroid cells exhibited nuclear foci of xeroderma pigmentosum group A (XPA), a unique nucleotide excision repair protein. Strikingly, these XPA foci colocalized with the DSB sites in the progeroid cells. This XPA-DSB association was further confirmed and found to be mediated by DNA, using a modified chromatin immunoprecipitation assay and coimmunoprecipitation. RNA interference (RNAi) knockdown of XPA in HGPS cells partially restored DSB repair as evidenced by Western blot analysis, immunofluorescence and comet assays. We propose that the uncharacteristic localization of XPA to or near DSBs inhibits DSB repair, thereby contributing to the premature aging phenotypes observed in progeria arising from genetic defects in prelamin A maturation.