Brecht Michael, Niemann Moritz, Schlüter Elke, Müller Ulrich F, Stuart Ken, Göringer H Ulrich
Department of Microbiology and Genetics, Darmstadt University of Technology, Schnittspahnstrasse 10, 64287 Darmstadt, Germany.
Mol Cell. 2005 Mar 4;17(5):621-30. doi: 10.1016/j.molcel.2005.01.018.
RNA editing in trypanosomatids is catalyzed by a high molecular mass RNP complex, which is only partially characterized. TbMP42 is a 42 kDa protein of unknown function that copurifies with the editing complex. The polypeptide is characterized by two Zn fingers and a potential barrel structure/OB-fold at its C terminus. Using recombinant TbMP42, we show that the protein can bind to dsRNA and dsDNA but fails to recognize DNA/RNA hybrids. rTbMP42 degrades ssRNA by a 3' to 5' exoribonuclease activity. In addition, rTbMP42 has endoribonuclease activity, which preferentially hydrolyzes non-base-paired uridylate-containing sequences. Gene silencing of TbMP42 inhibits cell growth and is ultimately lethal to the parasite. Mitochondrial extracts from TbMP42-minus trypanosomes have only residual RNA editing activity and strongly reduced endo-exoribonuclease activity. However, all three activities can be restored by the addition of rTbMP42. Together, the data suggest that TbMP42 contributes both endo- and exoribonuclease activity to the editing reaction cycle.
锥虫中的RNA编辑由一种高分子量核糖核蛋白复合体催化，该复合体仅得到部分表征。TbMP42是一种功能未知的42 kDa蛋白质，可与编辑复合体共纯化。该多肽的特征是在其C末端有两个锌指和一个潜在的桶状结构/OB折叠。使用重组TbMP42，我们发现该蛋白质可以结合双链RNA和双链DNA，但无法识别DNA/RNA杂交体。重组TbMP42通过3'到5'外切核糖核酸酶活性降解单链RNA。此外，重组TbMP42具有核糖核酸内切酶活性，优先水解含非碱基配对尿苷酸的序列。TbMP42的基因沉默会抑制细胞生长，并最终对寄生虫致死。来自TbMP42缺失型锥虫的线粒体提取物仅具有残余的RNA编辑活性，且内切-外切核糖核酸酶活性大幅降低。然而，通过添加重组TbMP42，所有这三种活性均可恢复。总体而言，这些数据表明TbMP42为编辑反应循环贡献了内切和外切核糖核酸酶活性。
