Chiu S M, Friedman L R, Oleinick N L
Department of Radiology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
Int J Radiat Biol. 1990 Aug;58(2):235-47. doi: 10.1080/09553009014551591.
The induction of DNA-protein crosslinks (DPC) was compared in gamma-irradiated metaphase and asynchronous Chinese hamster V79 cells. Unirradiated metaphase cells were found to have a higher level of background DPC than unirradiated asynchronous cells, and the metaphase cells were less susceptible to radiation-induced DPC production than were asynchronous cells. SDS-PAGE analysis of crosslinked proteins prepared from the two cell populations, both irradiated and unirradiated, showed very similar protein patterns. Crosslinked DNA was isolated and probed with radioactively labelled interphase poly(A+)RNA. The results indicated that the hypersensitivity of interphase actively transcribing DNA sequences to radiation-induced DPC formation was maintained at metaphase when the chromosomes are highly condensed. In contrast to asynchronous cells, radiation-induced DPC formed in metaphase cells were not removed during a 4 h post-irradiation period. However, metaphase cells appear to be able to remove the active DNA involved in DPC as indicated by a depletion of the probed sequences in the unrepaired DPC. Cell size analysis as well as cytological examination of the irradiated metaphase cells showed an absence of cell division during post-irradiation incubation. Furthermore, about 50% of the irradiated metaphase cells grew into giant cells which contain multiple nuclei and micronuclei, an indication of aberrant chromosome segregation.
在经γ射线辐照的中期和非同步化的中国仓鼠V79细胞中，对DNA-蛋白质交联（DPC）的诱导情况进行了比较。发现未辐照的中期细胞比未辐照的非同步化细胞具有更高水平的背景DPC，并且中期细胞比非同步化细胞对辐射诱导的DPC产生更不敏感。对来自辐照和未辐照的这两种细胞群体制备的交联蛋白进行SDS-PAGE分析，结果显示蛋白质模式非常相似。分离出交联的DNA并用放射性标记的间期聚（A+）RNA进行探测。结果表明，当染色体高度浓缩处于中期时，间期活跃转录的DNA序列对辐射诱导的DPC形成的超敏感性得以维持。与非同步化细胞相反，中期细胞中辐射诱导形成的DPC在辐照后4小时内未被去除。然而，如未修复的DPC中探测序列的减少所示，中期细胞似乎能够去除参与DPC的活性DNA。对辐照后的中期细胞进行细胞大小分析以及细胞学检查，结果显示在辐照后的培养过程中没有细胞分裂。此外，约50%的辐照中期细胞长成了含有多个细胞核和微核的巨细胞，这表明染色体分离异常。
