Gopalakrishnan T V, Thompson E B
J Cell Physiol. 1977 Oct;93(1):69-79. doi: 10.1002/jcp.1040930110.
The role of the nucleus in bringing about the induction of tyrosine aminotransferase (TAT) by glucocorticosteroid hormone and its deinduction upon steroid removal has been studied in enucleated rat hepatoma tissue culture cells (FU5-5). Both processes require the presence of the nucleus. However, cytoplasts from preinduced cells show an initial rapid decline in enzyme activity immediately after enucleation followed by maintenance of a constant level of activity. This initial decline in enzyme activity can be partially prevented by trypan blue, an inhibitor of lysosomal activity. This suggests that the early fall in enzyme activity could be due to an increase in the level of lysosomal activity immediately after enucleation. The subsequent constant level of activity seems due to maintenance rather than synthesis and degradation since it is not affected by cycloheximide. The absence of degradation applies to other kinds of proteins in enucleated FU5-5 cells and enucleated mouse fibroblast L cells. These experiments suggest that some kind of labile RNA or protein dependent on the presence of the nucleus is required for the degradation of all classes of proteins in different kinds of cells.
细胞核在糖皮质激素诱导酪氨酸转氨酶（TAT）以及去除类固醇后使其去诱导过程中的作用，已在去核大鼠肝癌组织培养细胞（FU5-5）中进行了研究。这两个过程都需要细胞核的存在。然而，来自预诱导细胞的胞质体在去核后立即显示出酶活性的初始快速下降，随后保持恒定的活性水平。溶酶体活性抑制剂台盼蓝可部分阻止酶活性的这种初始下降。这表明酶活性的早期下降可能是由于去核后溶酶体活性水平的增加。随后的恒定活性水平似乎是由于维持而不是合成和降解，因为它不受环己酰亚胺的影响。去核的FU5-5细胞和去核的小鼠成纤维细胞L细胞中其他种类蛋白质也不存在降解现象。这些实验表明，不同类型细胞中所有类别的蛋白质降解都需要某种依赖于细胞核存在的不稳定RNA或蛋白质。
