Splicing of yeast aI5beta group I intron requires SUV3 to recycle MRS1 via mitochondrial degradosome-promoted decay of excised intron ribonucleoprotein (RNP).
Yeast Suv3p is a member of the DEXH/D box family of RNA helicases and is a critical component of the mitochondrial degradosome, which also includes a 3' --> 5' exonuclease, Dss1p. Defects in the degradosome result in accumulation of aberrant transcripts, unprocessed transcripts, and excised group I introns. In addition, defects in SUV3 result in decreased splicing of the aI5beta and bI3 group I introns. Whereas a role for Suv3p in RNA degradation is well established, the function of Suv3p in splicing of group I introns has remained elusive. It has been particularly challenging to determine if Suv3p effects group I intron splicing through RNA degradation as part of the degradosome, or has a direct role in splicing as a chaperone, because nearly all perturbations of SUV3 or DSS1 result in loss of the mitochondrial genome. Here we utilized the suv3-1 allele, which is defective in RNA metabolism and yet maintains a stable mitochondrial genome, to investigate the role of Suv3p in splicing of the aI5beta group I intron. We provide genetic evidence that Mrs1p is a limiting cofactor for aI5beta splicing, and this evidence also suggests that Suv3p activity is required to recycle the excised aI5beta ribonucleoprotein. We also show that Suv3p acts indirectly as a component of the degradosome to promote aI5beta splicing. We present a model whereby defects in Suv3p result in accumulation of stable, excised group I intron ribonucleoproteins, which result in sequestration of Mrs1p, and a concomitant reduction in splicing of aI5beta.
Turk
Edward M
EM
Center for RNA Molecular Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA. emt11@case.edu
Caprara
Mark G
MG
D000483:Alleles; D017398:Alternative Splicing; D001483:Base Sequence; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D007438:Introns; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry; D012331:RNA, Fungal / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry; D012261:Ribonucleoproteins / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
C078505:MRS1 protein, S cerevisiae; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D012331:RNA, Fungal; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins; C075918:SUV3 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases