Minka D F, Nath J
Biochem Genet. 1981 Apr;19(3-4):199-210. doi: 10.1007/BF00504267.
Human cells irradiated with UV light synthesize lower molecular weight DNA than unirradiated cells. This reduction in molecular weight is greater in xeroderma pigmentosum (XP) cells than in normal cells. The molecular weight of DNA is further reduced by the addition of caffeine to XP cells. By several hours after irradiation, DNA fragments are barely detectable. Cells from excision-proficient and excision-deficient XP patients were studied autoradiographically to produce cytological evidence of DNA chain elongation. Replicate cultures with and without caffeine were synchronized and irradiated with UV light during the S phase. Caffeine was removed in G2, and the cells were labeled with 3H-thymidine. Results showed significantly increased labeling during G2 of excision-deficient XP cells. Labeling was dependent on the time of irradiation and presence of caffeine. The XP variant cells had no increase in labeling for any irradiation time.
用紫外线照射的人类细胞比未照射的细胞合成的DNA分子量更低。在着色性干皮病（XP）细胞中，这种分子量的降低比正常细胞中更明显。向XP细胞中添加咖啡因会进一步降低DNA的分子量。照射后几个小时，几乎检测不到DNA片段。对切除功能正常和切除功能缺陷的XP患者的细胞进行放射自显影研究，以产生DNA链延长的细胞学证据。将有咖啡因和无咖啡因的重复培养物同步化，并在S期用紫外线照射。在G2期去除咖啡因，并用3H-胸腺嘧啶核苷标记细胞。结果显示，切除功能缺陷的XP细胞在G2期的标记显著增加。标记取决于照射时间和咖啡因的存在。对于任何照射时间，XP变异细胞的标记都没有增加。
