Takagaki Y, Manley J L
Department of Biological Sciences, Columbia University, New York, New York 10027.
Nature. 1994 Dec 1;372(6505):471-4. doi: 10.1038/372471a0.
Polyadenylation of messenger RNA precursors is a complex process that requires multiple protein factors (for reviews, see refs 1, 2). Cleavage stimulation factor (CstF) is one of these, functioning together with cleavage-polyadenylation specificity factor, two cleavage factors, and poly(A)+ polymerase. CstF is composed of three subunits of M(r) 77, 64 and 50K. The 64K and 50K subunits contain, respectively, an RNP-type RNA-binding domain that contacts the pre-mRNA and transducin repeats characteristic of G-protein beta-subunits. Here we report the cloning and characterization of the 77K subunit of human CstF (referred to as 77K). We show that the 77K subunit is required for formation of active CstF and bridges the 64K and 50K subunits. Sequence analyses indicate that the 77K subunit is the homologue of the protein encoded by the Drosophila melanogaster suppressor of forked (su(f)) gene. Mutations in su(f) can enhance or suppress the effects of transposable element insertions, and our data indicate that this is due to changes in polyadenylation. Both the 77K subunit and the su(f) protein share homology with Saccharomyces cerevisiae RNA14, previously shown to be involved in mRNA metabolism. Our results thus also indicate that components of the complex polyadenylation machinery are conserved from yeast to man.
信使核糖核酸前体的聚腺苷酸化是一个复杂的过程，需要多种蛋白质因子（有关综述，请参见参考文献1、2）。切割刺激因子（CstF）就是其中之一，它与切割-聚腺苷酸化特异性因子、两种切割因子以及聚（A）+聚合酶共同发挥作用。CstF由分子量为77K、64K和50K的三个亚基组成。64K和50K亚基分别包含一个RNP型RNA结合结构域，该结构域与前体信使核糖核酸接触，并具有G蛋白β亚基特有的转导素重复序列。在此，我们报告了人类CstF 77K亚基（简称为77K）的克隆及特性分析。我们发现77K亚基是活性CstF形成所必需的，并且连接着64K和50K亚基。序列分析表明，77K亚基是果蝇叉状抑制基因（su(f)）编码的蛋白质的同源物。su(f)基因的突变能够增强或抑制转座元件插入的效应，我们的数据表明这是由于聚腺苷酸化的改变所致。77K亚基和su(f)蛋白都与酿酒酵母的RNA14具有同源性，先前已表明RNA14参与信使核糖核酸的代谢。因此，我们的研究结果还表明，复杂的聚腺苷酸化机制的组成成分在从酵母到人类的进化过程中是保守的。
