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  • 1
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Mitochondria ; Cytochrome c oxidase subunit 1 ; RNA processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Eighteen nuclear mutants of the yeast Saccharomyces cerevisiae, each disturbed in the biosynthesis of the mitochondrially encoded cytochrome c oxidase subunit 1 (cox 1) and each representing a distinct complementation group, have been examined to identify the level at which COX1 expression is affected. RNA blotting revealed that most have a defect in the processing of COX1 precursor-mRNA; only a few are defective in COX1 transcription and/or pre-mRNA stability. In most RNA-processing mutants, the absence of the COX1 messenger results from a defect in the splicing of one or more COX1 introns. In turn, this defect can be ascribed to a mutation in a nuclear gene which is either directly involved in splicing or else acts indirectly by impairing COX1 translation.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 30 (1996), S. 367-380 
    ISSN: 1432-0983
    Keywords: Key words Mitochondrial proteases ; Protein turnover ; Proteolysis ; Chaperones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It has been known for a long time that mitochondria contain their own protein-degradation systems. Only recently, however, have genes for mitochondrial proteases been identified and the powerful techniques of molecular biology been applied to gain insight into the role of protein degradation in mitochondrial biogenesis. It is now clear that the mitochondrial proteases that are involved in the initial stages of degradation are similar to prokaryotic ATP-dependent proteases, and that a division of labour exists between soluble and membrane-bound systems. These systems are essential for the biogenesis of fully functional mitochondria. Their natural targets are currently being identified, and their co-operation with chaperones and possible dual functions as chaperones/proteases are being investigated.
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  • 3
    ISSN: 1432-0983
    Keywords: RNA splicing ; RNA maturase ; Cytochrome c oxidase subunit I ; Group II introns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have characterized two yeast mutants deficient in the splicing of transcripts of the mitochondrial gene for cytochrome c oxidase subunit I (coxI). Both map to the first intron (aI1). RNA blot analysis shows that in addition to a reduced (mutant M15-190) or blocked (mutant M12-193) excision of the mutated intron aI1, the mutants are unable to excise the adjacent aI2 intron, the reading frame of which displays an amino acid sequence similarity to all. Splicing of the downstream introns is not affected, however. Sequence analysis of the first mutant DNA (M12-193) reveals a premature termination of the intron-encoded open reading frame, followed by two alterations at a short distance downstream. The other (M15-190) contains 11 separate changes. Although these occur in the intron reading frame, their main effect on RNA splicing may be exerted through the disturbance of intron secondary structure proposed for the 5′ end of several group II introns. The implications of these findings in relation to maturase function and structure of intron aI1 are discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 4 (1981), S. 167-171 
    ISSN: 1432-0983
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The flowering dogwood trees and green lawns of Cold Spring Harbor provided the setting for a meeting devoted to Mitochondrial Genes from May 13-17th, 1981. Dedicated to the memory of Boris Ephrussi, who pioneered mitochondrial genetics at a time when the only kinds of genetics were nuclear or unclear, the meeting showed that the study of mtDNA has had impact on many areas of molecular biology including the genetic code and decoding, tRNA function, mechanisms of splicing and molecular evolution. Curiously, as Herschel Roman pointed out in his opening address, Ephrussi took great pains to avoid any mention of mitochondrial DNA in connection with his observations on cytoplasmic inheritance, preferring instead to refer to ‘cytoplasmic particles, endowed with genetic continuity’ (Ephrussi 1953). This reticence was not shared by participants at the meeting, as the following, brief report will show.
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  • 5
    ISSN: 1432-0983
    Keywords: RNA processing ; Yeast mitochondria ; mit− mutants ; RNA splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mit− mutants disturbed in the synthesis of cytochrome c oxidase subunit I lack the mRNA for this protein and accumulate longer RNAs still containing intron sequences. We have analyzed the patterns of transcripts occurring in several such mutants in an attempt to define a pathway of processing events and to demarcate intron-sequences involved in RNA splicing. We find that processing does not follow a strictly ordered pathway and, in contrast to the situation for the cytochrome b gene, that a block in the processing of an intron does not necessarily lead to a block in the processing of introns downstream. Although in some cases, this may result from overlapping specificities of intronic-URF encoded RNA maturases, an internal start of translation on precursor RNAs seems more likely. M5-16, a mutant deleted for a large part of the central portion of the subunit I gene exhibits delayed processing and a highly simplified pattern of intermediates. The lengths of these indicate that maturation of the mRNA for subunit I involves processing, as well as splicing.
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  • 6
    ISSN: 1432-0983
    Keywords: Yeast ; QH2: cytochrome c oxidoreductase ; Mitochondrial biogenesis ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In Saccharmmyces cerevisiae, the COR2 gene codes for the 40 kDa subunit II of the QH2: cytochrome c oxidoreductase, an enzyme of the mitochondrial respiratory chain. Regions in the 5′ flank of this gene important for regulated expression were identified by assaying β-galactosidase activities in cells carrying different COR2-lacZ fusion genes. Sequences downstream of position-201 relative to the translational initiation codon are sufficient to confer regulation by carbon source, whereas sequences downstream of position-153 do not give rise to significant expression. A binding site for the abundant general transcription factor GFI is present in the region between-201 and-153 just upstream from sequences which resemble the consensus DNA recognition sequence of the regulatory protein complex HAP2/HAP3: 5′-TNATTGGT-3′. By quantitating RNA levels and assaying β-galactosidase activities we show that synthesis of COR2, which is not a hemoprotein, is regulated by HAP1, HAP2/HAP3 and heme.
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  • 7
    ISSN: 1432-0983
    Keywords: Key words Multi-copy suppression ; Mitochondrial membrane ; Metalloprotease ; S. cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The AFG3 gene of Saccharomyces cerevisiae encodes a mitochondrial inner membrane protein with ATP-dependent protease activity. To gain more insight into the function of this protein, multi-copy suppressors of an afg3-null mutation were isolated. Three genes were found that restored partial growth on non-fermentable carbon sources, all of which affect the biogenesis of respiratory competent mitochondria: PIM1(LON) encodes a matrix-localized ATP-dependent protease involved in the turnover of matrix proteins; OXA1(PET1402) encodes a putative mitochondrial inner membrane protein involved in the biogenesis of the respiratory chain; and MBA1 encodes a mitochondrial protein required for optimal respiratory growth. All three genes also suppressed a null mutation in a related gene, RCA1, as well as in the combination of afg3- and rca1-null.
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  • 8
    ISSN: 1432-0983
    Keywords: Key words MSS51 ; Mitochondrial translation ; Yeast ; Cytochrome c oxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Mutants of Saccharomyces cerevisiae that lack a functional MSS51 gene are respiratory deficient due to the absence of cytochrome c oxidase subunit 1 (Cox1p). It has been previously suggested, but not formally proven, that Mss51p is required for translational activation of COX1 mRNA, rather than being involved in a subsequent step in the synthesis of Cox1p or its assembly into cytochrome c oxidase. Pulse-chase labelling experiments now show that the absence of detectable levels of Cox1p in mss51-null strains is indeed due to the lack of synthesis of Cox1p, and is not caused by reduced stability of the protein. To gain more insight into the exact function of Mss51p, we determined the subcellular localization of the protein. We were able to show that an epitope-tagged version of Mss51p (Mss51HA) complements the mutation and can be localized in mitochondria, where it is firmly associated with the mitochondrial inner membrane. In addition, we characterized the previously identified mutant allele mss51-3. Sequence analysis revealed the presence of a short open reading frame upstream of MSS51 resulting from the creation of an extra ATG startcodon.
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 344 (1990), S. 110-111 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 330 (1987), S. 313-314 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SINCE the pioneering work of Thomas Cech and his colleagues on the self-splicing reaction carried out by the precursor to the large ribosomal (r)RNA in the protozoan Tetrahymena, the principle of RNA catalysis has become a familiar one (see ref. 1 for a review). When incubated in a simple salt ...
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