Mutations in nuclear gene cyt-4 of Neurospora crassa result in pleiotropic defects in processing and splicing of mitochondrial RNAs.
The nuclear cyt-4 mutants of Neurospora crassa have been shown previously to be defective in splicing the group I intron in the mitochondrial large rRNA gene and in 3' end synthesis of the mitochondrial large rRNA. Here, Northern hybridization experiments show that the cyt-4-1 mutant has alterations in a number of mitochondrial RNA processing pathways, including those for cob, coI, coII and ATPase 6 mRNAs, as well as mitochondrial tRNAs. Defects in these pathways include inhibition of 5' and 3' end processing, accumulation of aberrant RNA species, and inhibition of splicing of both group I introns in the cob gene. The various defects in mitochondrial RNA synthesis in the cyt-4-1 mutant cannot be accounted for by deficiency of mitochondrial protein synthesis or energy metabolism, and they suggest that the cyt-4-1 mutant is defective in a component or components required for processing and/or turnover of a number of different mitochondrial RNAs. Defective splicing of the mitochondrial large rRNA intron in the cyt-4-1 mutant may be a secondary effect of failure to synthesize pre-rRNAs having the correct 3' end. However, a similar explanation cannot be invoked to account for defective splicing of the cob pre-mRNA introns, and the cyt-4-1 mutation may directly affect splicing of these introns.
Dobinson
K F
KF
Department of Molecular Genetics, Ohio State University, Columbus 43210.
Henderson
M
M
Kelley
R L
RL
Collins
R A
RA
Lambowitz
A M
AM
D015152:Blotting, Northern; D004591:Electrophoresis, Polyacrylamide Gel; D007438:Introns; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D009491:Neurospora / Q000235:genetics*; D009492:Neurospora crassa / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D012313:RNA / Q000096:biosynthesis*; D015347:RNA Probes; D012326:RNA Splicing; D015183:Restriction Mapping; D014158:Transcription, Genetic
D015347:RNA Probes; D012313:RNA