Rudé J M, Friedberg E C
Mutat Res. 1977 Mar;42(3):433-42. doi: 10.1016/s0027-5107(77)80047-x.
Rates of semiconservative DNA synthesis have been investigated in asynchronous xeroderma pigmentosum (XP), XP variant, and normal human skin fibroblasts using the technique of cellular autoradiography. In unirradiated cells, no differences in DNA synthesis rates were detected among the three cell strains. Exposure to UV radiation caused the rate of DNA synthesis to decrease for at least three hours in all three cell strains. In the normal cell strain, recovery of the DNA synthetic rate occurred at later times following a UV fluence of 5 J/m2. At this same UV fluence, recovery was absent in classical XP cells during a 24 h post-irradiation period while it was slower than normal in XP variant cells. When the UV fluence to classical XP and XP variant cells was reduced so that survival in all three cell strains was approximately the same (25%), recovery of the DNA synthetic rate was similar in all three cell strains. These results are discussed in terms of current models of DNA replication in UV-irradiated cells and indicate: (1) that pyrimidine dimers are very effective blocks to DNA synthesis and (2) that there is no inherent defect in semi-conservative DNA synthesis in either classical XP or XP variant cells which is independent of a defect in DNA repair capacity.
利用细胞放射自显影技术，对非同步化的着色性干皮病（XP）、XP变异型和正常人皮肤成纤维细胞中的半保留DNA合成速率进行了研究。在未受辐照的细胞中，未检测到这三种细胞株之间的DNA合成速率存在差异。暴露于紫外线辐射后，所有三种细胞株的DNA合成速率均下降至少三小时。在正常细胞株中，紫外线通量为5 J/m2后，DNA合成速率在稍后时间恢复。在相同的紫外线通量下，经典XP细胞在辐照后24小时内未恢复，而XP变异型细胞的恢复速度比正常细胞慢。当降低经典XP细胞和XP变异型细胞的紫外线通量，使所有三种细胞株的存活率大致相同（25%）时，所有三种细胞株的DNA合成速率恢复情况相似。根据目前紫外线辐照细胞中DNA复制的模型对这些结果进行了讨论，结果表明：（1）嘧啶二聚体是DNA合成的非常有效的阻断剂；（2）经典XP细胞或XP变异型细胞中的半保留DNA合成不存在与DNA修复能力缺陷无关的固有缺陷。
