Chu G, Berg P
Department of Medicine, Stanford University, CA 94305.
Mol Biol Med. 1987 Oct;4(5):277-90.
Xeroderma pigmentosum (XP) is an inherited disease characterized by the defective repair of DNA damaged by ultraviolet radiation and a number of chemicals. In this paper, plasmid DNA carrying a marker gene is cross-linked in vitro by the antitumor drug cisplatin and successfully introduced into tissue culture cells by both calcium phosphate coprecipitation and electroporation. Transient expression of the marker gene is greatly decreased in XP cells compared to wild-type. As few as seven lesions will inactivate the marker gene in XP cells. Furthermore, the biochemical defect must include an impaired capacity for repair of cisplatin-DNA intrastrand cross-links. Since the host cell itself is not exposed to chemical modification, a cisplatin cross-linked plasmid shuttle vector can be used as a specific probe for the DNA repair capacity of cultured cells. Paradoxically, when cisplatin cross-linked plasmid carrying the selectable marker neo is introduced into cells, there is an increase in the number of stable neo+ transformants in both XP and wild-type cells. Thus, cisplatin damage appears to stimulate the integration of transfected DNA into the host chromosome by a mechanism that is independent of the defective repair pathway in XP.
着色性干皮病（XP）是一种遗传性疾病，其特征在于对紫外线辐射和多种化学物质造成的DNA损伤修复存在缺陷。在本文中，携带标记基因的质粒DNA在体外被抗肿瘤药物顺铂交联，并通过磷酸钙共沉淀法和电穿孔法成功导入组织培养细胞。与野生型相比，XP细胞中标记基因的瞬时表达大幅降低。在XP细胞中，仅七个损伤就会使标记基因失活。此外，生化缺陷必定包括修复顺铂-DNA链内交联的能力受损。由于宿主细胞本身未受到化学修饰，顺铂交联的质粒穿梭载体可作为培养细胞DNA修复能力的特异性探针。矛盾的是，当将携带可选择标记neo的顺铂交联质粒导入细胞时，XP细胞和野生型细胞中稳定的neo+转化体数量均增加。因此，顺铂损伤似乎通过一种独立于XP中缺陷修复途径的机制刺激转染DNA整合到宿主染色体中。
