Meric F, Matsumoto K, Wolffe A P
Laboratory of Molecular Embryology, NICHD, National Institutes of Health, Bethesda, Maryland 20892-5431, USA.
J Biol Chem. 1997 May 9;272(19):12840-6. doi: 10.1074/jbc.272.19.12840.
We examine the translational regulation of histone H4 mRNA when Xenopus laevis oocytes are induced to mature with progesterone. Histone H4 mRNA synthesized from plasmid templates microinjected into oocyte nuclei is translationally silenced (masked). This masked mRNA becomes translationally active only after oocyte maturation. In contrast, histone H4 mRNA injected into the oocyte cytoplasm is translationally active both before and after oocyte maturation. Thus, transcription in vivo is required to mask histone H4 mRNA and to allow subsequent translational regulation. Protein association with histone H4 mRNA synthesized in vivo was determined before and after oocyte maturation. UV cross-linking of radiolabeled RNA to protein and immunoprecipitation of cross-linked proteins reveals an increased association of the chaperone nucleoplasmin with ribonucleoprotein particles dependent on the oocyte maturation process. The Y-box protein FRGY2 inhibits translation of histone H4 mRNA in vitro. Nucleoplasmin is able to partially relieve this repression. We discuss the potential role of nuleoplasmin in the remodeling of repressive ribonucleoprotein particles containing maternal mRNA to facilitate translational activation.
我们研究了非洲爪蟾卵母细胞在孕酮诱导下成熟时组蛋白H4 mRNA的翻译调控。从显微注射到卵母细胞核中的质粒模板合成的组蛋白H4 mRNA在翻译上是沉默的（被掩盖）。这种被掩盖的mRNA只有在卵母细胞成熟后才具有翻译活性。相比之下，注射到卵母细胞细胞质中的组蛋白H4 mRNA在卵母细胞成熟前后都具有翻译活性。因此，体内转录对于掩盖组蛋白H4 mRNA并允许后续的翻译调控是必需的。在卵母细胞成熟前后，测定了与体内合成的组蛋白H4 mRNA结合的蛋白质。将放射性标记的RNA与蛋白质进行紫外线交联以及对交联蛋白质进行免疫沉淀，结果显示伴侣蛋白核质素与核糖核蛋白颗粒的结合增加，这取决于卵母细胞的成熟过程。Y盒蛋白FRGY2在体外抑制组蛋白H4 mRNA的翻译。核质素能够部分缓解这种抑制作用。我们讨论了核质素在重塑含有母源mRNA的抑制性核糖核蛋白颗粒以促进翻译激活方面的潜在作用。
