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本实验通过5%过氯酸抽提、丙酮分级分离以及CM-Sephadex离子交换层析等步骤分别从正常大鼠肝和大鼠移植性肝癌(BERH-2)细胞核中获得了HMG蛋白,并且比较了它们的电泳和层析行为以及生物学作用,发现正常鼠肝和肝癌HMG没有明显的质的差别。比较了正常大鼠肝细胞核和BERH-2肝癌细胞核体外转录活性,并比较了DNA酶Ⅰ消化这两种细胞核的动力学和有限消化时释放出来的HMG和组蛋白H_1相对量的变化。发现肝癌细胞核转录活性明显高于正常大鼠肝细胞核;肝癌细胞核对DNA酶Ⅰ消化的敏感性大于正常肝细胞核;肝癌细胞核在DNA酶Ⅰ有限消化时HMG的释放较正常大鼠肝细胞核多。实验结果说明,在肝癌的细胞中HMG与正常肝细胞的HMG可能没有明显的质的差别,但与活性核小体结合的HMG量有所增加。这可能是肝癌染色质结构的改变,基因转录失常原因之一。
In this experiment, HMG protein was obtained from the nucleus of normal rat liver and rat transplanted liver cancer (BERH-2) by 5% perchloric acid extraction, acetone fractionation, and CM-Sephadex ion exchange chromatography, and compared. Their electrophoretic and chromatographic behaviors and biological effects revealed no significant qualitative differences between normal rat liver and HMG. The in vitro transcription activity of normal rat hepatocyte nuclei and BERH-2 hepatoma cell nuclei was compared, and the kinetics of the two nuclei of DNase I digestion and the relative amounts of HMG and histone H1 released during limited digestion were compared. It was found that the nuclear transcription activity of hepatocellular carcinoma cells was significantly higher than that of normal rat hepatocyte nuclei; the sensitivity of liver cancer cell nuclei to DNase I digestion was greater than that of normal liver nuclei; the release of HMG from hepatoma nuclei during limited digestion of DNase I was more than that of normal rat liver nuclei. The experimental results showed that there may be no significant qualitative difference between HMG and normal liver cells in HCC cells, but the amount of HMG bound to active nucleosomes increases. This may be a change in the structure of the chromatin of liver cancer, one of the reasons for the abnormal transcription of genes.