Rosenstein B S
Radiat Res. 1984 Nov;100(2):378-86.
DNA synthesis was examined in ultraviolet (uv)-irradiated ICR 2A frog cells in which either pyrimidine dimers or nondimer photoproducts represented the major class of DNA lesions. Dimers were induced by exposure of cells to 254 nm uv, while nondimer photoproducts were induced by irradiation of cells with uv produced by a fluorescent sunlamp (FSL) that was filtered through 48A Mylar (removes wavelengths less than 310 nm). The FSL-irradiated cultures were also treated with photoreactivating light (PRL) which removed most of the small number of dimers induced by the irradiation, leaving a relatively pure population of nondimer photoproducts. In addition, cells were exposed to 60Co gamma rays. The cultures were pulse-labeled and the size distribution of the DNA synthesized was estimated using both sucrose gradient sedimentation and alkaline step elution. Using either of these techniques, it was found that the presence of dimers resulted in a reduction principally in the synthesis of high molecular weight (MW) DNA. In contrast, nondimer photoproducts caused a strong inhibition in the synthesis of low MW DNA, as was also observed in gamma-irradiated cells. Hence the induction of pyrimidine dimers in DNA mainly affected the elongation of replicons, whereas nondimer lesions primarily caused an inhibition of replicon initiation.
在紫外线（uv）照射的ICR 2A蛙细胞中检测DNA合成，其中嘧啶二聚体或非二聚体光产物代表主要的DNA损伤类型。通过将细胞暴露于254 nm紫外线诱导二聚体，而通过经48A聚酯薄膜过滤的荧光太阳灯（FSL）产生的紫外线照射细胞诱导非二聚体光产物（去除波长小于310 nm的光）。FSL照射的培养物也用光复活光（PRL）处理，该光去除了照射诱导的少数二聚体中的大部分，留下相对纯净的非二聚体光产物群体。此外，细胞暴露于60Coγ射线。对培养物进行脉冲标记，并使用蔗糖梯度沉降和碱性分步洗脱法估计合成的DNA的大小分布。使用这两种技术中的任何一种，都发现二聚体的存在主要导致高分子量（MW）DNA合成减少。相比之下，非二聚体光产物对低MW DNA的合成有强烈抑制作用，这在γ射线照射的细胞中也有观察到。因此，DNA中嘧啶二聚体的诱导主要影响复制子的延伸，而非二聚体损伤主要导致复制子起始的抑制。
