The human Imp3 and Imp4 proteins form a ternary complex with hMpp10, which only interacts with the U3 snoRNA in 60-80S ribonucleoprotein complexes
The human Imp3 and Imp4 proteins form a ternary complex with hMpp10, which only interacts with the U3 snoRNA in 60-80S ribonucleoprotein complexes
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DOI：
10.1093/nar/gkg300
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发表时间：
2003-04-01
影响因子：
14.9
通讯作者：
Pruijn, GJM
中科院分区：
文献类型：
--
作者：
Granneman, S;Gallagher, JEG;Pruijn, GJM
核糖体生物发生需要大量的反式作用因子，其中许多是前rRNA组分的化学修饰和加工所需的。U3 snoRNP复合物是pre-rRNA加工中早期切割步骤所需的。我们已经克隆了编码酵母U3 snoRNP相关蛋白Imp3和Imp 4的人类和小鼠同源物的cDNA。这两种人类蛋白质都定位于核仁并与U3 snoRNA相互作用。互补实验的结果表明，与小鼠Imp 4相比，小鼠Imp3可以部分减轻相应的酵母空菌株的生长缺陷，表明Imp3在pre-rRNA加工中的作用是进化保守的。密度梯度离心实验的结果表明，与hU 3 - 55 K相反，人Imp3和Imp 4蛋白主要与60- 80 S核糖核蛋白复合物中的U3 snoRNA相互作用。此外，我们还发现hImp 3、hImp 4和hMpp 10在体外可以形成稳定的异源三聚体复合物，该复合物是由hImp 3和hImp 4与hMpp 10直接相互作用产生的。hImp 3和hImp 4突变体的分析表明，它们与hMpp 10的结合与它们的核仁积累相关，这强烈表明，hImp 3，hImp 4和hMpp 10的三元复合物的形成是它们与核仁组分相关联所必需的。
Ribosome biogenesis requires a vast number of trans-acting factors many of which are required for the chemical modification and processing of the pre-rRNA component. The U3 snoRNP complex is required for the early cleavage steps in pre-rRNA processing. We have cloned cDNAs encoding the human and mouse homologs of the yeast U3 snoRNP-associated proteins Imp3 and Imp4. Both human proteins localize to nucleoli and interact with the U3 snoRNA. The results of complementation experiments show that, in contrast to mouse Imp4, mouse Imp3 can partially alleviate the growth defect of the corresponding yeast null strain, indicating that the role of Imp3 in pre-rRNA processing is evolutionarily conserved. The results of density gradient centrifugation experiments show that, in contrast to hU3-55K, the human Imp3 and Imp4 proteins predominantly interact with the U3 snoRNA in 60-80S ribonucleoprotein complexes. In addition, we have found that hImp3, hImp4 and hMpp10 can form a stable hetero-trimeric complex in vitro, which is generated by direct interactions of both hImp3 and hImp4 with hMpp10. The analysis of hImp3 and hImp4 mutants indicated that their binding to hMpp10 correlates with their nucleolar accumulation, strongly suggesting that the formation of the ternary complex of hImp3, hImp4 and hMpp10 is required for their association with nucleolar components.