大鼠老化过程大脑皮层细胞核、染色质转录研究

Studies on the Transcription of Nuclei and Chromatin Front Cerebral Cortex Neurons During Rat Aging

本实验对不同鼠龄(4—,16—17—,33—34—和99—103周)大鼠老化动物模型进行脑细胞核、染色质体外转录研究,结果表明:(1)大脑皮层细胞核、染色质转录活性在老化过程中呈下降趋势,其中RNA聚合酶Ⅰ、Ⅱ活性与染色质模板效率变化一致,说明染色质模板活性降低是导致细胞核转录功能减退的原因之一。(2)幼年鼠染色质RNA和NHCP含量高于老年鼠,提示染色质结合蛋白及RNA可能参与不同生理时期脑神经元染色质结构和功能的调节。(3)老年鼠脑染色质DNA抗DN-aseⅠ酶解能力增强,提示衰老导致转录活性染色质区域减少。

Male rats at different ages (4-,16-17-,33-34-and 99-103-week) were studied. Transcription in purified nuclei and chromatin from cerebral cortex neurons of these animals were determined by incorporation of 3H-UMP into RNA in vitro, the results showed that both transcriptional activity of nuclei and template efficiency of chromatin were gradually declined during aging, especially in young rats. Comparison of transcription levels by three types of RNA polymerases (RNA Pol) in rat aging, there was significant correlation between the changes of Pol Ⅰ and Ⅱ and endogenous template activity. Transcription of chromatin with exogenous E.coli RNA Pol showed that the age-related reduction in template efficiency of chromatin was one of the majar reasons which caused the decline of transcriptional activities of nuclei from cerebral cortex neurons.Further experiments showed that contents of RNA and NHCP in chromatin were also decreased during aging. By using nucleases (MCN and DNase I) as probe to study the conformation of chromatin showed the chromatin DNA in neurons from old rats was more resistent to DNase I digestion. These results may suggest that the number of transcription active regions in the chromatin and the chromatin function were both decreased by aging.