Dabauvalle M C, Franke W W
Proc Natl Acad Sci U S A. 1982 Sep;79(17):5302-6. doi: 10.1073/pnas.79.17.5302.
The specific nucleocytoplasmic compartmentalization of proteins has been examined for some major soluble acidic nuclear proteins in oocytes of different amphibia. Proteins synthesized and radioactively labeled by translation in vitro, by using mRNA from ovaries of the frog Xenopus laevis, were injected into the cytoplasm of living oocytes of Xenopus or of the salamander Pleurodeles waltlii. At various times after injection, nucleus and cytoplasm were manually separated and endogenous and injected proteins were analyzed by two-dimensional gel electrophoresis. We show that several major nucleus-specific proteins of different sizes and electrical charges, including the very acidic proteins N1 and N2 (Mr, 110,000 and 100,000) and N4 (Mr, 34,000), are identical in both forms--i.e., as translation products in vitro and as present in the nucleoplasm. We conclude that significantly different cytoplasmic precursor forms to these nuclear proteins do not exist. The experiments indicate that (i) the translation products contain the signal(s) directing the specific sequestration of these proteins within the nucleus, (ii) post-translational processing is not required for the accumulation of these proteins in the nucleoplasm, and (iii) the signals and the mechanisms involved are not species specific.
针对不同两栖动物卵母细胞中的一些主要可溶性酸性核蛋白，研究了其特定的核质区室化情况。利用非洲爪蟾卵巢的mRNA，通过体外翻译合成并进行放射性标记的蛋白质，被注射到非洲爪蟾或美西螈活卵母细胞的细胞质中。注射后在不同时间，手动分离细胞核和细胞质，并通过二维凝胶电泳分析内源性和注射的蛋白质。我们发现，几种大小和电荷不同的主要核特异性蛋白，包括极酸性蛋白N1和N2（分子量分别为110,000和100,000）以及N4（分子量为34,000），在两种形式下是相同的，即作为体外翻译产物和存在于核质中的形式。我们得出结论，这些核蛋白不存在明显不同的细胞质前体形式。实验表明：（i）翻译产物包含将这些蛋白质特异性隔离在细胞核内的信号；（ii）这些蛋白质在核质中积累不需要翻译后加工；（iii）所涉及的信号和机制不是物种特异性的。
