Welting Tim J M, Peters Florence M A, Hensen Sanne M M, van Doorn Nienke L, Kikkert Bastiaan J, Raats Jos M H, van Venrooij Walther J, Pruijn Ger J M
Department of Biomolecular Chemistry, Nijmegen Center for Molecular Life Sciences, Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen, The Netherlands.
RNA. 2007 Jan;13(1):65-75. doi: 10.1261/rna.237807. Epub 2006 Nov 21.
Rpp20 and Rpp25 are subunits of the human RNase MRP and RNase P endoribonucleases belonging to the Alba superfamily of nucleic acid binding proteins. These proteins, which bind very strongly to each other, transiently associate with RNase MRP. Here, we show that the Rpp20-Rpp25 heterodimer is resistant to both high concentrations of salt and a nonionic detergent. The interaction of Rpp20 and Rpp25 with the P3 domain of the RNase MRP RNA appeared to be strongly enhanced by their heterodimerization. Coimmunoprecipitation experiments demonstrated that only a single copy of each of these proteins is associated with the RNase MRP and RNase P particles in HEp-2 cells. Both proteins accumulate in the nucleoli, which in case of Rpp20 is strongly dependent on its interaction with Rpp25. Finally, the results of overexpression and knock-down experiments indicate that their expression levels are codependent. Taken together, these data indicate that the Rpp20-Rpp25 heterodimerization regulates their RNA-binding activity, subcellular localization, and expression, which suggests that their interaction is also crucial for their role in RNase MRP/P function.
Rpp20和Rpp25是人类核糖核酸酶MRP和核糖核酸酶P内切核糖核酸酶的亚基，属于核酸结合蛋白的阿尔巴超家族。这些蛋白质彼此结合非常紧密，与核糖核酸酶MRP短暂结合。在这里，我们表明Rpp20-Rpp25异二聚体对高浓度盐和非离子去污剂均具有抗性。Rpp20和Rpp25与核糖核酸酶MRP RNA的P3结构域的相互作用似乎因其异二聚化而大大增强。免疫共沉淀实验表明，在HEp-2细胞中，这些蛋白质各自只有一个拷贝与核糖核酸酶MRP和核糖核酸酶P颗粒相关联。这两种蛋白质都在核仁中积累，就Rpp20而言，这在很大程度上取决于其与Rpp25的相互作用。最后，过表达和敲低实验结果表明它们的表达水平相互依赖。综上所述，这些数据表明Rpp20-Rpp25异二聚化调节它们的RNA结合活性、亚细胞定位和表达，这表明它们的相互作用对于它们在核糖核酸酶MRP/P功能中的作用也至关重要。
