Kick D, Barrett P, Cummings A, Sommerville J
Nucleic Acids Res. 1987 May 26;15(10):4099-109. doi: 10.1093/nar/15.10.4099.
The stored mRNP particles of Xenopus oocytes contain protein kinase activity and two major phosphoproteins of 60 kDa (pp60) and 56 kDa (pp56). These proteins can be phospholabelled in the particles either in vivo or in vitro and then isolated by SDS-PAGE. On renaturing pp60 in the presence of globin mRNA, a stable RNA-protein complex is formed. The complex has a uniform density in Cs salt gradients, corresponding to the binding of about 10 protein molecules to each mRNA, probably at the poly(A) sequence. Compared with uncomplexed mRNA, the RNP complex is translated poorly both in vitro and in vivo. Translation of the complex can be regained after treatment with protein phosphatase. It is shown that dephosphorylation destabilizes the binding of protein to RNA, making the mRNA accessible for translation. Studies with native mRNP particles show that their translation also can be enhanced by dephosphorylation.
非洲爪蟾卵母细胞中储存的mRNP颗粒含有蛋白激酶活性以及两种主要的磷酸化蛋白，分子量分别为60 kDa（pp60）和56 kDa（pp56）。这些蛋白在颗粒中可在体内或体外进行磷酸标记，然后通过SDS-PAGE分离。在珠蛋白mRNA存在的情况下使pp60复性时，会形成一种稳定的RNA-蛋白复合物。该复合物在Cs盐梯度中具有均匀的密度，这对应于每个mRNA大约结合10个蛋白分子，可能是在poly(A)序列处。与未复合的mRNA相比，RNP复合物在体外和体内的翻译效率都很低。用蛋白磷酸酶处理后，复合物的翻译能力可以恢复。结果表明，去磷酸化会破坏蛋白与RNA的结合，使mRNA能够进行翻译。对天然mRNP颗粒的研究表明，去磷酸化也可以增强它们的翻译能力。
