van Eenennaam H, Pruijn G J, van Venrooij W J
Department of Biochemistry, University of Nijmegen, PO Box 9101, NL-6500 HB Nijmegen, The Netherlands.
Nucleic Acids Res. 1999 Jun 15;27(12):2465-72. doi: 10.1093/nar/27.12.2465.
RNase MRP is a ribonucleoprotein particle involved in the processing of pre-rRNA. The RNase MRP particle is structurally highly related to the RNase P particle, which is involved in pre-tRNA processing. Their RNA components fold into a similar secondary structure and they share several protein subunits. We have identified and characterised human and mouse cDNAs that encode proteins homologous to yPop4p, a protein subunit of both the yeast RNase MRP and RNase P complexes. The human Pop4 cDNA encodes a highly basic protein of 220 amino acids. Transfection experiments with epitope-tagged hPop4 protein indicated that hPop4 is localised in the nucleus and accumulates in the nucleolus. Immunoprecipitation assays using extracts from transfected cells expressing epitope-tagged hPop4 revealed that this protein is associated with both the human RNase MRP and RNase P particles. Polyclonal rabbit antibodies raised against recombinant hPop4 recognised a 30 kDa protein in total HeLa cell extracts and specifically co-immunoprecipitated the RNA components of the RNase MRP and RNase P complexes. Finally we showed that anti-hPop4 immunoprecipitates possess RNase P enzymatic activity. Taken together, these data show that we have identified a protein that represents the human counterpart of the yeast Pop4p protein.
核糖核酸酶MRP是一种参与前体rRNA加工的核糖核蛋白颗粒。核糖核酸酶MRP颗粒在结构上与参与前体tRNA加工的核糖核酸酶P颗粒高度相关。它们的RNA组分折叠成相似的二级结构，并且共享几个蛋白质亚基。我们已经鉴定并表征了人类和小鼠的cDNA，这些cDNA编码与酵母核糖核酸酶MRP和核糖核酸酶P复合物的蛋白质亚基yPop4p同源的蛋白质。人类Pop4 cDNA编码一个由220个氨基酸组成的高度碱性的蛋白质。用表位标签化的hPop4蛋白进行的转染实验表明，hPop4定位于细胞核并在核仁中积累。使用表达表位标签化hPop4的转染细胞提取物进行的免疫沉淀分析表明，该蛋白与人类核糖核酸酶MRP和核糖核酸酶P颗粒都相关。针对重组hPop4产生的兔多克隆抗体在总的HeLa细胞提取物中识别出一个30 kDa的蛋白质，并特异性地共免疫沉淀核糖核酸酶MRP和核糖核酸酶P复合物的RNA组分。最后我们表明，抗hPop4免疫沉淀物具有核糖核酸酶P的酶活性。综上所述，这些数据表明我们已经鉴定出一种代表酵母Pop4p蛋白人类对应物的蛋白质。
