title: Uncoupling the roles of the SUV3 helicase in maintenance of mitochondrial genome stability and RNA degradation.
abstract: Yeast SUV3 is a nuclear encoded mitochondrial RNA helicase that complexes with an exoribonuclease, DSS1, to function as an RNA degradosome. Inactivation of SUV3 leads to mitochondrial dysfunctions, such as respiratory deficiency; accumulation of aberrant RNA species, including excised group I introns; and loss of mitochondrial DNA (mtDNA). Although intron toxicity has long been speculated to be the major reason for the observed phenotypes, direct evidence to support or refute this theory is lacking. Moreover, it remains unknown whether SUV3 plays a direct role in mtDNA maintenance independently of its degradosome activity. In this paper, we address these questions by employing an inducible knockdown system in Saccharomyces cerevisiae with either normal or intronless mtDNA background. Expressing mutants defective in ATPase (K245A) or RNA binding activities (V272L or ΔCC, which carries an 8-amino acid deletion at the C-terminal conserved region) resulted in not only respiratory deficiencies but also loss of mtDNA under normal mtDNA background. Surprisingly, V272L, but not other mutants, can rescue the said deficiencies under intronless background. These results provide genetic evidence supporting the notion that the functional requirements of SUV3 for degradosome activity and maintenance of mtDNA stability are separable. Furthermore, V272L mutants and wild-type SUV3 associated with an active mtDNA replication origin and facilitated mtDNA replication, whereas K245A and ΔCC failed to support mtDNA replication. These results indicate a direct role of SUV3 in maintaining mitochondrial genome stability that is independent of intron turnover but requires the intact ATPase activity and the CC conserved region.
authors.affiliation: Department of Biological Chemistry, University of California, Irvine, California 92697.
authors.forename: Xuning Emily
authors.initials: XE
authors.lastname: Guo
authors.affiliation: Department of Biological Chemistry, University of California, Irvine, California 92697.
authors.forename: Chi-Fen
authors.initials: CF
authors.lastname: Chen
authors.affiliation: Department of Biological Chemistry, University of California, Irvine, California 92697.
authors.forename: Dennis Ding-Hwa
authors.initials: DD
authors.lastname: Wang
authors.affiliation: Department of Biological Chemistry, University of California, Irvine, California 92697.
authors.forename: Aram Sandaldjian
authors.initials: AS
authors.lastname: Modrek
authors.affiliation: Department of Biological Chemistry, University of California, Irvine, California 92697.
authors.forename: Vy Hoai
authors.initials: VH
authors.lastname: Phan
authors.affiliation: Department of Biological Chemistry, University of California, Irvine, California 92697. Electronic address: whlee@uci.edu.
authors.forename: Wen-Hwa
authors.initials: WH
authors.lastname: Lee
authors.affiliation: Department of Biological Chemistry, University of California, Irvine, California 92697. Electronic address: plchen@uci.edu.
authors.forename: Phang-Lang
authors.initials: PL
authors.lastname: Chen
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D003062:Codon; D017124:Conserved Sequence; D053487:DEAD-box RNA Helicases / Q000378:metabolism / Q000502:physiology*; D054629:Genome, Mitochondrial; D007438:Introns; D008564:Membrane Potentials; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D012313:RNA / Q000235:genetics; D020365:RNA Helicases / Q000235:genetics; D020871:RNA Stability; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D003062:Codon; D029701:Saccharomyces cerevisiae Proteins; D012313:RNA; D000255:Adenosine Triphosphate; C075918:SUV3 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases