Pratt R E, Johnson L F
Biochim Biophys Acta. 1980 Jul 29;608(2):332-43. doi: 10.1016/0005-2787(80)90179-3.
To better understand the mechanism by which the rate of protein synthesis is regulated in growth-stimulated mouse 3T6 fibroblasts, we have determined the proportion of cytoplasmic poly(A)(+) mRNA that is associated with polysomes. We found that this proportion is nearly the same (70-80%)in resting, serum-stimulatd, or exponentially growing cells. This indicates that the increase in the rate of protein synthesis following serum stimulation of 3T6 cells is regulated primarily by the increase in mRNA content rather than by an increase in the fraction of total mRNA engaged in protein synthesis. We also show that in detergent-lysed 3T6 cells, up to half of the subpolysomal poly(A)(+) mRNA is of mitochondrial origin. This conclusion is based on analysis of the size of the mRNA and its poly(A), its subcellular location and the inhibition of the labeling of this mRNA by ethidium bromide. The physical properties of subpolysomal mRNA of nuclear origin are similar to those of polysomal mRNA.
为了更好地理解生长刺激的小鼠3T6成纤维细胞中蛋白质合成速率的调控机制，我们测定了与多核糖体相关的细胞质聚腺苷酸（poly(A)）⁺ mRNA的比例。我们发现，在静止、血清刺激或指数生长的细胞中，这一比例几乎相同（70 - 80%）。这表明血清刺激3T6细胞后蛋白质合成速率的增加主要是由mRNA含量的增加所调控，而不是由参与蛋白质合成的总mRNA比例的增加所调控。我们还表明，在去污剂裂解的3T6细胞中，多达一半的亚多核糖体聚腺苷酸（poly(A)）⁺ mRNA源自线粒体。这一结论基于对mRNA及其聚腺苷酸的大小、亚细胞定位以及溴化乙锭对该mRNA标记的抑制作用的分析。核起源的亚多核糖体mRNA的物理性质与多核糖体mRNA的相似。
