Journal of Biological Chemistry
Volume 278, Issue 3, 17 January 2003, Pages 1603-1611
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RNA: STRUCTURE METABOLISM AND CATALYSIS
The Yeast Mitochondrial Degradosome: ITS COMPOSITION, INTERPLAY BETWEEN RNA HELICASE AND RNase ACTIVITIES AND THE ROLE IN MITOCHONDRIAL RNA METABOLISM*

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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.

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Published, JBC Papers in Press, November 7, 2002, DOI 10.1074/jbc.M208287200

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This work was supported in part by State Committee for Scientific Research Grants 6P04 00319 and 6P04 01818, the Polish-French Center for Biotechnology of Plants EU Centre of Excellence in Molecular Biology Grant ICA-CT-2000-70010, and Faculty of Biology Grant BW.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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Supported by a Foundation for Polish Science fellowship for young scientists and an EMBO short-term fellowship for work at University of Amsterdam.

Current address: Dept. of Endocrinology and Reproduction, Faculty of Medicine and Health Sciences, P. O. Box 1738, 3000 DR Rotterdam, The Netherlands

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Current address: EMBO, Meyerhofstrasse 1, 69117 Heidelberg, Germany