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本文观察了外加的HMG对体外核转录和DNA酶Ⅰ消化不同状态细胞核的影响,并与功能已经比较清楚、组成和结构较为相似的组蛋白H_1进行比较,发现:(1)外加的HMG与组蛋白H_1均能抑制肝细胞核的转录活性,但它们的抑制作甩以组蛋白H_1最强,磷酸化组蛋白H_1其次,HMG最弱。(2)组蛋白H_1能抑制DNA酶Ⅰ对肝细胞核的消化,而外加的HMG对小鼠肝细胞核消化的影响呈双相:短暂消化时HMG能降低细胞核对DNA酶Ⅰ的敏感性,但其抑制作用较H_1弱;延长消化时反而能增加核对DNA酶Ⅰ的敏感性。(3)组蛋白H_1对DNA酶Ⅰ有限消化后的残核消化无明显的影响而HMG能促进残核的消化。(4)组蛋白H_1能抑制DNA酶Ⅰ消化去组蛋白H_1细胞核,而HMG能促进去组蛋白H_1的细胞核的消化。实验结果启示HMG非组蛋白与组蛋白H_1相对置的变化会引起染色质结构的改变,从而影响转录的进行,这可能是基因表达粗调节的一种方式。HMG能增加非活性核小体对DNA酶Ⅰ的敏感性说明HMG很可能与活性核小体结构的形成有关。
In this paper, we observed the effects of HMG on nuclear translocation and DNase Ⅰ digestion in different states, and compared with the histone H_1 whose function was relatively clear and whose composition and structure were similar. The results showed that: (1) Protein H_1 can inhibit the transcriptional activity of liver cell nucleus, but their inhibitory action is the strongest of histone H_1, phosphorylated histone H_1 secondly, HMG is the weakest. (2) H 1 inhibited the digestion of hepatocyte nucleus by DNase Ⅰ, while the addition of HMG had a biphasic effect on hepatic nuclear digestion in mice: HMG decreased the susceptibility of DNA nuclei to DNase Ⅰ during transient digestion, Inhibition is weaker than H_1; prolonged digestion but can increase the sensitivity of DNase Ⅰ check. (3) Histone H_1 had no obvious effect on the residual digestion of DNase Ⅰ after limited digestion, while HMG could promote the digestion of residual nucleus. (4) H 1 can inhibit DNase Ⅰ digestion to histone H_1 nucleus, while HMG can promote the digestion of histone H_1 nucleus. The experimental results suggest that the relative change of HMG non-histone and histone H 1 will lead to the change of chromatin structure, which will affect the transcription. This may be a way of rough regulation of gene expression. HMG can increase the sensitivity of inactive nucleosomes to DNase Ⅰ, indicating that HMG is probably related to the formation of active nucleosomes.