DNA CROSSLINKING INDUCED BY X-RAYS AND CHEMICAL AGENTS
DNA CROSSLINKING INDUCED BY X-RAYS AND CHEMICAL AGENTS
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DOI：
10.1016/0005-2787(77)90253-2
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发表时间：
1977-01-01
期刊：
影响因子：
--
通讯作者：
LITTLE, JB
中科院分区：
文献类型：
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作者：
FORNACE, AJ;LITTLE, JB
用碱洗脱法测定人二倍体成纤维细胞DNA的交联度。用已知的DNA交联剂(HN_2，丝裂霉素-C)处理细胞后，在0度的小剂量X射线照射下，可控制DNA链断裂的频率。预先用交联剂处理的效果是以剂量依赖的方式降低DNA洗脱率。细胞经X射线照射后，37度孵育2小时。C以允许大部分诱导的DNA链断裂重新连接，然后暴露在0度的小测试剂量的X射线下。C、DNA洗脱速率降低。这种X射线诱导的DNA交联效应的大小依赖于X射线的初始剂量(1-60krad)，并在低氧条件下被辐射增强。在5krad X射线照射2小时后，与暴露在1微米氮芥末中30分钟时的交联度相似。有证据表明，交联在X射线照射后立即发生，并在37度孵化后修复。由于用蛋白酶处理细胞裂解物消除了这种作用，因此X射线交联被归因于DNA-蛋白质的交联。用碱性洗脱法可以在更大的范围(25rad-10krad)上测量X射线诱导的DNA单链断裂，当用酶消化消除这种交联效应时。
DNA crosslinking was measured in human diploid fibroblasts by alkaline elution. Following treatment of the cells by known DNA crosslinking agents (HN2, mitomycin-C), a controlled frequency of DNA strand breaks was induced by a small test dose of X-rays at 0.degree. C. The effect of the prior treatment with a crosslinking agent was to reduce the rate of DNA elution in a dose dependent manner. When cells were X-irradiated, incubated for 2 h at 37.degree. C in order to permit rejoining of most of the induced DNA strand breaks, and then exposed to the small test dose of X-rays at 0.degree. C, a reduction in the rate of DNA elution occurred. The magnitude of this X-ray induced DNA crosslink effect was dependent upon the initial dose of X-rays (1-60 krad), and was increased by irradiation under hypoxic conditions. A similar level of crosslinking was present 2 h after 5 krad of X-ray as was present with a 30 min exposure to a 1 .mu.M nitrogen mustard. Evidence is presented that crosslinking occurs immediately after X-irradiation and is repaired with incubation at 37.degree. C. X-ray crosslinking was attributed to DNA-protein crosslinks since treatment of the cell lysates with proteinase removed the effect. X-ray induced DNA single strand breaks can be measured over an increased range (25 rad-10 krad) by alkaline elution when the crosslink effect is first removed by proteinase digestion.