Dexter T J, Bennett D C
Exp Cell Res. 1987 Jan;168(1):255-64. doi: 10.1016/0014-4827(87)90433-2.
There is evidence for cytoplasmic control over gene expression in cell differentiation, but still very little is known of the intracellular mechanism, nuclear, cytoplasmic, or both, which actively initiates the differentiation of one cell type into another. Here the role of the cytoplasm was examined in the induction of differentiation of cultured mouse melanoma cells by melanocyte-stimulating hormone and alkaline medium. Intact cells were compared with cytoplasts, cells enucleated by centrifugation in the presence of cytochalasin D (CD). Surprisingly, early inductions of pigment (melanin) synthesis and of the principal melanin-synthesizing enzyme activity, tyrosinase, could be achieved in cytoplasts. Indeed these early changes were slower in nucleated cells and were accelerated by the inhibitor of protein synthesis, cycloheximide. Thus the initial activation of tyrosinase and melanin synthesis--although not necessarily any other or later aspects of melanoma cell differentiation--is apparently controlled through a labile, transcription- and translation-dependent repression. To our knowledge this is a novel mechanism for the initiation of differentiation; its generality remains to be tested.
有证据表明在细胞分化过程中细胞质对基因表达具有控制作用，但对于积极启动一种细胞类型向另一种细胞类型分化的细胞内机制（细胞核、细胞质或两者皆有）仍知之甚少。在此，研究了在黑素细胞刺激素和碱性培养基诱导培养的小鼠黑素瘤细胞分化过程中细胞质的作用。将完整细胞与胞质体进行比较，胞质体是在细胞松弛素D（CD）存在下通过离心去核的细胞。令人惊讶的是，在胞质体中可以实现色素（黑色素）合成和主要黑色素合成酶活性（酪氨酸酶）的早期诱导。实际上，这些早期变化在有核细胞中较慢，并且被蛋白质合成抑制剂环己酰亚胺加速。因此，酪氨酸酶和黑色素合成的初始激活——尽管不一定是黑素瘤细胞分化的任何其他或后期方面——显然是通过不稳定的、依赖转录和翻译的抑制来控制的。据我们所知，这是一种启动分化的新机制；其普遍性仍有待检验。
