Liu J, Yang S L, Xu B
Shanghai Institute of Materia Medica, Chinese Academy of Sciences.
Sci China B. 1990 Dec;33(12):1459-65.
The effects of lycobetaine (LBT) on DNA single strand break and chromatin conformation were examined by in-situ nick translation method. It was found that LBT did not cause DNA single strand break. After 2-h incubation of murine hepatoma cells with 1-50 micrograms/ml LBT in vitro, the chromatin transcription activity was inhibited gradually. This effect was time- and dose-dependent. Actinomycin D produced a similar effect; 10-hydroxycamptothecin not only caused DNA single strand break, but also altered chromatin conformation; homoharringtonine had no marked influence on either. By molecular hybridization technique, it was found that the effect of LBT on individual genes was somewhat different. After 2-h incubation of the cells with LBT, the sensitivities of c-myc, N-ras, and beta 2-microglobulin genes to DNase I were decreased from 75 +/- 6, 66 +/- 4, 70 +/- 8% to 28 +/- 8, 25 +/- 5, 28 +/- 7%, respectively, while that of c-myb and beta-globin genes (8 + 6%, 6 + 5%) did not change obviously.
采用原位缺口平移法检测了番茄碱（LBT）对DNA单链断裂和染色质构象的影响。结果发现，LBT不会引起DNA单链断裂。在体外将小鼠肝癌细胞与1 - 50微克/毫升的LBT孵育2小时后，染色质转录活性逐渐受到抑制。这种作用具有时间和剂量依赖性。放线菌素D产生了类似的作用；10 - 羟基喜树碱不仅导致DNA单链断裂，还改变了染色质构象；高三尖杉酯碱对两者均无明显影响。通过分子杂交技术发现，LBT对各个基因的作用有所不同。细胞与LBT孵育2小时后，c - myc、N - ras和β2 - 微球蛋白基因对DNase I的敏感性分别从75±6%、66±4%、70±8%降至28±8%、25±5%、28±7%，而c - myb和β - 珠蛋白基因的敏感性（8±6%，6±5%）无明显变化。
