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  • 1
    Electronic Resource
    Electronic Resource
    A point mutation in the 5′-untranslated leader that affects translational activation of the mitochondrial COX 3 mRNA (1995)
    Springer
    Current genetics 28 (1995), S. 60-66 
    Details
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Translation ; mRNA 5′-leader
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 613-base 5′-untranslated leader (5′-UTL) of the Saccharomyces cerevisiae mitochondrial COX 3 mRNA contains the target of an mRNA-specific translational activator complex composed of at least three nuclearly encoded proteins. We have genetically mapped a collection of cox 3 point mutations, using a set of defined COX 3 deletions, and found one to be located in the region coding the 5′-UTL. The strain carrying this allele was specifically defective in translation of the COX 3 mRNA. Nucleotide-sequence analysis showed that the allele was in fact a double mutation comprised of a single-base insertion in the 5′-UTL (T inserted between bases-428 and-427 with respect to the start of translation) and a G to A substitution at+3 that changed the ATG initiation codon to ATA. Both mutations were required to block translation completely. The effects of the ATG to ATA mutation alone (cox 3-1) had previously been analyzed in this laboratory: it reduces, but does not eliminate, translation, causing a slow respiratory growth phenotype. The T insertion in the 5′-UTL had no detectable respiratory growth phenotype as a single mutation. However, the 5′-UTL insertion mutation enhanced the respiratory defective phenotype of missense mutations in pet 54, one of the COX 3-specific translational-activator genes. This phenotypic enhancement suggests that the-400 region of the 5′-UTL, where the mutation is located, is important for Pet54p-COX 3 mRNA interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00311882
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  • 2
    Electronic Resource
    Electronic Resource
    Primary structure of wild-type and mutant alleles of the PET494 gene of Saccharomyces cerevisiae (1986)
    Springer
    Molecular genetics and genomics 202 (1986), S. 294-301 
    Details
    ISSN: 1617-4623
    Keywords: Mitochondria ; Translation ; Frameshift suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The product of the yeast nuclear gene PET494 is required specifically for the translation of the mitochondrially encoded subunit III of cytochrome c oxidase. We have determined the DNA sequence of a 1.9 kb fragment carrying PET494. The sequence contains a single long open reading frame of 489 codons. This open reading frame encodes the PET494 protein since the DNA sequence of the corresponding fragment derived from a strain with a known pet494 amber mutation contained an in frame UAG codon. The results of S1 nuclease protection experiments demonstrated that this region is transcribed and that the 5′ ends of the major transcripts lie 30 to 40 base-pairs upstream of the first AUG codon in the PET494 reading frame. The predicted PET494 protein has a highly basic amino-terminal domain of 66 amino acids followed by a stretch of 32 uncharged residues, half of which are hydrophobic. The remainder of the protein is not unusual in amino acid composition or distribution except that the carboxyterminal region is notably basic. The phenotype of mutations generated in vitro around codon 119 by exonuclease digestion and linker insertion indicated that this region is dispensable for function. A mutation caused by deletion of 101 bp of coding sequence behaved like a simple frameshift when inserted into the chromosome: it was partially suppressed by the recessive non-group specific frameshift suppressor suf13 and reverted to Pet+ phenotype by mutations liked to PET494.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331654
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  • 3
    Electronic Resource
    Electronic Resource
    The yeast nuclear gene CBS1 is required for translation of mitochondrial mRNAs bearing the cob 5′ untranslated leader (1987)
    Springer
    Molecular genetics and genomics 206 (1987), S. 45-50 
    Details
    ISSN: 1617-4623
    Keywords: Mitochondria ; mRNA leader ; Positive control ; Translation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mitochondrial translation of the cob mRNA to yield apocytochrome b is specifically dependent on the nuclear gene CBS1, while mitochondrial translation of the oxi2 mRNA to yield cytochrome oxidase subunit III (cox III) is specifically dependent on the nuclear gene PET494. Chimeric oxi2 mRNAs bearing the 5′ leaders of other mitochondrial mRNAs, transcribed from rho - mitochondrial DNAs termed MSU494, are translated in pet494 mutants. In this study, we examined translation of coxIII from MSU494-encoded chimeric mRNAs in zygotes of defined nuclear and mitochondrial genotype. CoxIII was translated from a chimeric mRNA bearing the cob leader only when the zygotes contained a wild-type CBS1 gene. CoxIII translation from an mRNA bearing the 5′ leader of the mitochondrial gene aap1 was not dependent on CBS1 activity. We conclude that the product of the nuclear gene CBS1, or something under its control, acts in the mitochondrion on the cob mRNA 5′ leader to activate translation of downstream coding sequences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326534
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  • 4
    Electronic Resource
    Electronic Resource
    Reduced but accurate translation from a mutant AUA initiation codon in the mitochondrial COX2 mRNA of Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 383-390 
    Details
    ISSN: 1617-4623
    Keywords: Mitochondria ; Translation ; Yeast ; PET111 ; PET2858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have changed the translation initiation codon of the COX2 mRNA of Saccharomyces cerevisiae from AUG to AUA, generating a mutation termed cox2-10. This mutation reduced translation of the COX2 mRNA at least five-fold without affecting the steady-state level of the mRNA, and produced a leaky nonrespiratory growth phenotype. To address the question of whether residual translation of the cox2-10 mRNA was initiating at the altered initiation codon or at the next AUG codon downstream (at position 14), we took advantage of the fact that the mature coxll protein is generated from the electrophoretically distinguishable coxII precursor by removal of the amino-terminal 15 residues, and that this processing can be blocked by a mutation in the nuclear gene PET2858. We constructed a pet2858, cox2-10 double mutant strain using a pet2858 allele from our mutant collection. The double mutant accumulated low levels of a polypeptide which comigrated with the coxII precursor protein, not the mature species, providing strong evidence that residual initiation was occurring at the mutant AUA codon. Residual translation of the mutant mRNA required the COX2 mRNA-specific activator PET111. Furthermore, growth of cox2-10 mutant strains was sensitive to alterations in PET111 gene dosage: the respiratory-defective growth phenotype was partially suppressed in haploid strains containing PET111 on a high-copy-number vector, but became more severe in diploid strains containing only one functional copy of PET111.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00281787
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  • 5
    Electronic Resource
    Electronic Resource
    Suppression of carboxy-terminal truncations of the yeast mitochondrial mRNA-specific translational activator PET122 by mutations in two new genes, MRP17 and PET127 (1992)
    Springer
    Molecular genetics and genomics 235 (1992), S. 64-73 
    Details
    ISSN: 1617-4623
    Keywords: Mitochondria ; Translation ; Ribosomal protein ; Suppression ; Genetic map
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The PET122 protein is one of three Saccharomyces cerevisiae nuclear gene products required specifically to activate translation of the mitochondrially coded COX3 mRNA. We have previously observed that mutations which remove the carboxy-terminal region of PET122 block translation of the COX3 mRNA but can be suppressed by unlinked nuclear mutations in several genes, two of which have been shown to code for proteins of the small subunit of mitochondrial ribosomes. Here we describe and map two more new genes identified as allele-specific suppressors that compensate for carboxy-terminal truncation of PET122. One of these genes, MRP17, is essential for the expression of all mitochondrial genes and encodes a protein of Mr 17343. The MRP17 protein is a component of the small ribosomal subunit in mitochondria, as demonstrated by the fact that a missense mutation, mrp17-1, predicted to cause a charge change indeed alters the charge of a mitochondrial ribosomal protein of the expected size. In addition, mrp17-1, in combination with some mutations affecting another mitochondrial ribosomal protein, caused a synthetic defective phenotype. These findings are consistent with a model in which PET122 functionally interacts with the ribosomal small subunit. The second new suppressor gene described here, PET127, encodes a protein too large (Mr 95900) to be a ribosomal protein and appears to operate by a different mechanism. PET127 is not absolutely required for mitochondrial gene expression and allele-specific suppression of pet122 mutations results from the loss of PET127 function: a pet127 deletion exhibited the same recessive suppressor activity as the original suppressor mutation. These findings suggest the possibility that PET127 could be a novel component of the mitochondrial translation system with a role in promoting accuracy of translational initiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286182
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