Recovery of DNA Synthesis from Inhibition by Ultraviolet Light in Mammalian Cells
Recovery of DNA Synthesis from Inhibition by Ultraviolet Light in Mammalian Cells
复制标题
哺乳动物细胞中 DNA 合成从紫外线抑制中恢复
DOI：
10.1242/jcs.1984.supplement_6.13
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发表时间：
1987
影响因子：
4
通讯作者：
R. Meneghini
中科院分区：
文献类型：
--
作者：
A. M. Ventura;J. M. Ortega;R. Schumacher;R. Meneghini
摘要 一般而言，在大多数嘧啶二聚体从基因组中去除之前，哺乳动物细胞就可以从紫外线 (u.v) 的 DNA 合成抑制中恢复过来。这是一个复杂的现象，其生物学意义尚未得到充分评估。在中国仓鼠 V79 细胞中，这种恢复似乎与双链 DNA 延伸率的提高直接相关。紫外线照射后，DNA 聚合酶 α 抑制剂阿菲迪霉素 (aphidicolin) 的存在辐射产生两种不同的反应。在低浓度下，足以抑制95%的DNA复制，但对切除修复没有影响，该药物对恢复没有影响。这表明恢复不需要持续的复制性 DNA 合成。在较高浓度的阿菲迪霉素足以阻止切除修复时，恢复现象被阻止。抑制 60% RNA 合成的浓度的放线菌素 D 也可以阻止恢复。在定量放射自显影实验中，先前照射的细胞与未照射的细胞融合，后者的细胞核表现出对紫外线抑制的更高抵抗力。比来自非融合细胞的细胞核。这些结果表明：（1）即使V79细胞（相对于人类细胞）表现出较低的修复率，对于恢复也很重要；尽管在DNA合成恢复后，大多数二聚体仍保留在V79基因组中，但去除染色质某些重要区域的病变或修复过程本身的活性对于恢复很重要； (2)恢复机制是诱导性的，依赖于RNA的合成和特定因子的产生。最后，我们观察到先前用氟脱氧尿苷处理的细胞对紫外线的抑制变得更有抵抗力。照射后，这些细胞比未处理的细胞复制 DNA 的速度更快。由于已证明该药物可激活中国仓鼠细胞中未使用的复制起点，从而减小平均复制子大小，因此我们假设获得性耐药性与大量较小复制子的操作有关。这也可能是在紫外线照射后从抑制中恢复的机制。辐照。
SUMMARY In general mammalian cells recover from DNA synthesis inhibition by ultraviolet light (u.v.) before most of the pyrimidine dimers have been removed from the genome. This is a complex phenomenon whose biological significance has not been fully assessed. In Chinese hamster V79 cells this recovery seems to be directly coupled to an enhanced rate of double-stranded DNA elongation. The presence of the DNA polymerase α inhibitor, aphidicolin, after u.v. irradiation produces two different responses. At low concentration, sufficient to inhibit 95 % of DNA replication but having no effect on excision repair, the drug has no effect on the recovery. This shows that ongoing replicative DNA synthesis is not required for recovery. At higher concentrations of aphidicolin, sufficient to block excision repair, the recovery phenomenon was prevented. The recovery was also prevented by actinomycin D at a concentration that inhibits 60 % of RNA synthesis. In quantitative autoradiography experiments in which previously irradiated cells were fused with unirradiated cells the nuclei of the latter exhibited a higher resistance to inhibition by u.v. than nuclei from non-fused cells. These results indicate that: (1) even the low repair rate exhibited by V79 cells (relative to human cells) is important for recovery; although most of the dimers remain in the V79 genome after recovery of DNA synthesis, either the removal of lesions from some important region of chromatin or the activity of the repair process itself is important for the recovery; (2) the recovery mechanism is induced and depends on RNA synthesis and the production of specific factors. Finally, we have observed that cells previously treated with fluorodeoxyuridine become more resistant to inhibition by u.v. After irradiation these cells replicate DNA faster than untreated cells. Since it has been shown that this drug activates unused origins of replication in Chinese hamster cells, reducing the average replicon size, we assume that the acquired resistance has to do with the operation of a larger number of smaller replicons. This may also be the mechanism whereby recovery from inhibition occurs after u.v. irradiation.