Dziembowski Andrzej, Piwowarski Jan, Hoser Rafal, Minczuk Michal, Dmochowska Aleksandra, Siep Michel, van der Spek Hans, Grivell Les, Stepien Piotr P
Department of Genetics, Warsaw University and Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5A, 02-106 Warsaw, Poland.
J Biol Chem. 2003 Jan 17;278(3):1603-11. doi: 10.1074/jbc.M208287200. Epub 2002 Nov 7.
The yeast mitochondrial degradosome (mtEXO) is an NTP-dependent exoribonuclease involved in mitochondrial RNA metabolism. Previous purifications suggested that it was composed of three subunits. Our results suggest that the degradosome is composed of only two large subunits: an RNase and a RNA helicase encoded by nuclear genes DSS1 and SUV3, respectively, and that it co-purifies with mitochondrial ribosomes. We have found that the purified degradosome has RNA helicase activity that precedes and is essential for exoribonuclease activity of this complex. The degradosome RNase activity is necessary for mitochondrial biogenesis but in vitro the degradosome without RNase activity is still able to unwind RNA. In yeast strains lacking degradosome components there is a strong accumulation of mitochondrial mRNA and rRNA precursors not processed at 3'- and 5'-ends. The observed accumulation of precursors is probably the result of lack of degradation rather than direct inhibition of processing. We suggest that the degradosome is a central part of a mitochondrial RNA surveillance system responsible for degradation of aberrant and unprocessed RNAs.
酵母线粒体降解体（mtEXO）是一种参与线粒体RNA代谢的NTP依赖性外切核糖核酸酶。先前的纯化研究表明它由三个亚基组成。我们的研究结果表明，降解体仅由两个大亚基组成：分别由核基因DSS1和SUV3编码的一种核糖核酸酶和一种RNA解旋酶，并且它与线粒体核糖体共同纯化。我们发现，纯化的降解体具有RNA解旋酶活性，该活性先于并对该复合物的外切核糖核酸酶活性至关重要。降解体的核糖核酸酶活性对于线粒体生物发生是必需的，但在体外，没有核糖核酸酶活性的降解体仍然能够解开RNA。在缺乏降解体成分的酵母菌株中，线粒体mRNA和rRNA前体在3'和5'末端未加工，大量积累。观察到的前体积累可能是缺乏降解的结果，而不是加工的直接抑制。我们认为，降解体是线粒体RNA监测系统的核心部分，负责降解异常和未加工的RNA。
