CHO mutant UV61 removes (6-4) photoproducts but not cyclobutane dimers.
CHO mutant UV61 removes (6-4) photoproducts but not cyclobutane dimers.
复制标题
CHO 突变体 UV61 去除 (6-4) 光产物，但不去除环丁烷二聚体。
DOI：
10.1093/mutage/4.2.140
复制
发表时间：
1989
期刊：
影响因子：
2.7
通讯作者：
Johnson,RT
中科院分区：
文献类型：
--
作者：
Thompson,LH;Mitchell,DL;Regan,JD;Bouffler,SD;Stewart,SA;Carrier,WL;Nairn,RS;Johnson,RT
CHO突变体UV 61先前被指定为UV敏感啮齿动物细胞突变体的互补组6。UV 61对紫外线辐射的杀伤敏感性低于突变体如UV 5，后者在作用于紫外线诱导的损伤的切割过程中存在高度缺陷。细胞存活的D37在UV 61下为0.4J/m2，而亲本AA 8系为10 J/m2，UV 5下为0.2J/m2。类似地，在hprt和aprt位点的突变诱导显示对UV 61的中间响应。在复制后恢复测定中，在UV 61中的UV照射后，脉冲标记的新生DNA的成熟动力学是正常的。从碱性洗脱和碱性解旋测定的数据表明，断裂积累和复位率，测量照射后0-120分钟，也是正常的突变体。这种修复切口与使用放射免疫测定法测量的UV 61中嘧啶（6-4）嘧啶酮光产物的快速、正常去除相关，该放射免疫测定法对此类损伤具有特异性。相反，暴露于10或15 J/m2后，在UV 61中没有发现可检测到的环丁烷二聚体从DNA中的去除，而AA 8细胞在24 h时去除了32%。我们认为，在UV 61的突变，特别是降低了修复蛋白的亲和力环丁烷二聚体，这也是无效地从正常CHO细胞的散装DNA。UV 61对直接作用化学品7-溴甲基苯并[a]蒽的杀伤抗性仅略大于UV 5，表明除了环丁烷二聚体之外，大体积化学加合物的修复缺陷。我们得出结论，（6-4）光产物在CHO细胞中具有细胞毒性和致突变性，并且在UV照射后早期观察到的切割事件是由（6-4）光产物而不是环丁烷二聚体的修复引起的。
The CHO mutant UV61 was previously assigned to complementation group 6 of UV-sensitive rodent cell mutants. UV61 is less sensitive to killing by UV radiation than mutants such as UV5, which is highly defective in the incision process that acts on UV-induced lesions. The D37for cell survival is ∼4 J/m2for UV61, compared with 10 J/m2for the parental AA8 line and ∼2 J/m2for UV5. Similarly, mutation induction at thehprtandaprtloci shows an intermediate response to UV61. In a post-replication recovery assay, the kinetics of maturation of pulse-labelled nascent DNA were normal after UV irradiation in UV61. Data from alkaline elution and alkaline unwinding assays showed that the rates of break accumulation and reseating, measured 0–120 min after irradiation, were also normal in the mutant. This repair incision correlated with the rapid, normal removal of pyrimidine(6–4)pyrimidone photoproducts in UV61 measured using a radioimmunoassay that is specific for this class of damage. In contrast, after exposure to 10 or 15 J/m2, no detectable removal of cyclobutane dimers from DNA was found in UV61 while AA8 cells removed 32% by 24 h. We suggest that the mutation in UV61 specifically lowers the affinity of a repair protein for cyclobutane dimers, which are also inefficiently removed from the bulk DNA of normal CHO cells. The resistance of UV61 to killing by the direct acting chemical 7-bromomethylbenz[a]anthracene was only slightly greater than that of UV5, indicating defective repair of bulky chemical adducts in addition to cyclobutane dimers. We conclude that (6–4) photoproducts are both cytotoxic and mutagenic in CHO cells and that the incision events observed early after UV-irradiation result from the repair of (6–4) photoproducts rather than cyclobutane dimers.