Khochbin S, Principaud E, Chabanas A, Lawrence J J
Unite INSERM 309 Département de Recherche Fondamentale, CEN Grenoble, France.
J Mol Biol. 1988 Mar 5;200(1):55-64. doi: 10.1016/0022-2836(88)90333-6.
Oncogenes may play a crucial role in the genetic program of cellular differentiation; even, probably, at a very early stage in this program, which can be described as pre-commitment. We have investigated the variation in, and the control level of, the accumulation of the transformation-associated cellular protein p53 in murine erythroleukemia cells induced to differentiate by hexamethylene bisacetamide. Using flow cytofluorimetry after double staining of the cells, we have found that p53 decreased from two hours after the input of the inducer, to reach a basal level of about 30% of the starting value. The stability of the protein was found to be affected neither by the inducer nor by the position of the cells in the cell cycle. Looking for the regulation mechanism of the p53 decay, we found that the mRNA started to decrease as early as half an hour after the hexamethylene bisacetamide was put in the culture medium, and that the transcription rate of the gene itself could not account for the observed down-regulation of the mRNA, suggesting a post-transcriptional control for the mRNA accumulation. This control did not require the de-novo synthesis of a protein component, as shown by cycloheximide experiments, but seemed to be governed by the induced synthesis of an RNA molecule. Hypothetical models for such a regulation process are discussed in the light of recent reports on the metabolism of mRNA.
癌基因可能在细胞分化的遗传程序中发挥关键作用；甚至可能在该程序的非常早期阶段，即可以被描述为预决定阶段发挥作用。我们研究了用六亚甲基双乙酰胺诱导分化的小鼠红白血病细胞中与转化相关的细胞蛋白p53的积累变化及其控制水平。在对细胞进行双重染色后使用流式细胞荧光术，我们发现从加入诱导剂两小时后p53开始下降，降至起始值的约30%的基础水平。发现该蛋白的稳定性既不受诱导剂影响，也不受细胞在细胞周期中所处位置的影响。在寻找p53降解的调控机制时，我们发现早在六亚甲基双乙酰胺加入培养基半小时后mRNA就开始下降，并且该基因本身的转录速率无法解释所观察到的mRNA下调，这表明mRNA积累存在转录后调控。如环己酰亚胺实验所示，这种调控不需要蛋白质成分的从头合成，但似乎受一种RNA分子的诱导合成所支配。根据最近关于mRNA代谢的报道讨论了这种调控过程的假设模型。
