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Gene Review

COX3  -  cytochrome c oxidase subunit 3

Saccharomyces cerevisiae S288c

Synonyms: Cytochrome c oxidase polypeptide III, Cytochrome c oxidase subunit 3, OXI2, Q0275
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Disease relevance of COX3


High impact information on COX3

  • We have unambiguously assigned the alpha-event senDNA (the 2.6 kb monomer) to the oxi3 gene locus and the beta-event senDNA to the oxi2 gene locus [2].
  • Accumulation of mitochondrially synthesized Saccharomyces cerevisiae Cox2p and Cox3p depends on targeting information in untranslated portions of their mRNAs [3].
  • In this study, we tested whether chimeric mRNAs with the untranslated sequences normally present on the mRNA encoding soluble Var1p, can direct functional expression of coding sequences specifying the integral membrane proteins Cox2p and Cox3p [3].
  • Contrary to the belief that editing is absent from bryophytes, here we report mitochondrial RNA editing in cox3 mRNA of the liverwort Pellia epiphylla, the mosses Tetraphis pellucida and Ceratodon purpureus and the hornwort Anthroceros crispulus [4].
  • Mitochondrial translation of the oxi2 mRNA, encoding yeast cytochrome c oxidase subunit III (coxIII), has previously been shown to specifically require the mitochondrially located protein product of the nuclear gene PET494 [5].

Biological context of COX3

  • Two blocks of RNA sequence present in COX3 have similar counterparts within intron aI5 beta of COX1 [6].
  • One such revertant carried a missense mutation in the PET122 gene that was a strong and dominant suppressor of the cold-sensitive defect in the mRNA, indicating that the PET122 protein interacts functionally (possibly directly) with the COX3 mRNA 5' leader [7].
  • To bridge this gap a synthetic gene, ARG8m, designed to specify an arginine biosynthetic enzyme when expressed inside mitochondria, has been inserted into yeast mtDNA in place of the COX3 structural gene [8].
  • This mitochondrial cox3::ARG8m gene fully complements a nuclear arg8 deletion at the level of cell growth, and it is dependent for expression upon nuclear genes that encode subunits of the COX3 mRNA-specific translational activator [8].
  • Expression of the yeast mitochondrial genes COX1 and COX3, which encode subunits I and III of cytochrome oxidase, respectively, is controlled by a common nuclear-encoded trans-acting factor [9].

Anatomical context of COX3

  • COX3 mRNA-specific translational activator proteins are associated with the inner mitochondrial membrane in Saccharomyces cerevisiae [10].
  • 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 [11].
  • This decrease leads to low steady-state levels of Cox1p, Cox2p, and Cox3p, loss of visible spectra of aa(3) cytochromes, and low cytochrome c oxidase activity in mutant mitochondria [12].

Associations of COX3 with chemical compounds

  • Importantly, transcript levels from the mitochondrial OLI1 gene, which has an associated organellar UAS, were attenuated in the DeltaYJR127C mutant during glycerol-based growth, but those from COX3 (OXI2), which lacks an associated mitochondrial UAS, were not [13].
  • Analysis of mitochondrial RNA in cytoplasmic petite mutants containing the oxi2 gene, but with varying lengths of flanking sequences, suggest the presence of a common promoter for oxi2 and the upstream valine tRNA [14].
  • A mitochondrial cox3 gene in the alkane yeast, Yarrowia lipolytica, encodes a subunit-3 protein of cytochrome c oxidase, and contains a 1044 base-pair-long intron, as compared with the corresponding intronless gene in Saccharomyces cerevisiae [15].

Regulatory relationships of COX3

  • The data are consistent with models in which the PET494 protein acts within the mitochondria to specifically promote the translation of the oxi2 messenger RNA [16].

Other interactions of COX3

  • The core of the cytochrome c oxidase complex is composed of its three largest subunits, Cox1p, Cox2p, and Cox3p, which are encoded in mitochondrial DNA of Saccharomyces cerevisiae and inserted into the inner membrane from the inside [17].
  • Interestingly, the OXA1 gene, located on the yeast chromosome VIII, is adjacent to the gene PET 122, which controls the initiation of cox3 mRNA translation [18].
  • Therefore, the PET122 gene product is a protein required for the expression of COX3 at some step after transcription and 5'-end processing of its transcript [19].
  • Furthermore, a nonsense mutation introduced near the beginning of the PET54 open reading frame abolished both COX1 and COX3 gene expression [20].
  • Two regions of the wild-type mtDNA (between cyb and oli2 and between SrRNA and oxi2) appear to be dispensable for mitochondrial function [21].

Analytical, diagnostic and therapeutic context of COX3


  1. Use of atp6 in fungal phylogenetics: an example from the boletales. Kretzer, A.M., Bruns, T.D. Mol. Phylogenet. Evol. (1999) [Pubmed]
  2. Are mitochondrial structural genes selectively amplified during senescence in Podospora anserina? Wright, R.M., Horrum, M.A., Cummings, D.J. Cell (1982) [Pubmed]
  3. Accumulation of mitochondrially synthesized Saccharomyces cerevisiae Cox2p and Cox3p depends on targeting information in untranslated portions of their mRNAs. Sanchirico, M.E., Fox, T.D., Mason, T.L. EMBO J. (1998) [Pubmed]
  4. RNA editing in bryophytes and a molecular phylogeny of land plants. Malek, O., Lättig, K., Hiesel, R., Brennicke, A., Knoop, V. EMBO J. (1996) [Pubmed]
  5. At least two nuclear gene products are specifically required for translation of a single yeast mitochondrial mRNA. Costanzo, M.C., Seaver, E.C., Fox, T.D. EMBO J. (1986) [Pubmed]
  6. Disruption of the yeast nuclear PET54 gene blocks excision of mitochondrial intron aI5 beta from pre-mRNA for cytochrome c oxidase subunit I. Valencik, M.L., Kloeckener-Gruissem, B., Poyton, R.O., McEwen, J.E. EMBO J. (1989) [Pubmed]
  7. Suppression of a defect in the 5' untranslated leader of mitochondrial COX3 mRNA by a mutation affecting an mRNA-specific translational activator protein. Costanzo, M.C., Fox, T.D. Mol. Cell. Biol. (1993) [Pubmed]
  8. Expression of a recoded nuclear gene inserted into yeast mitochondrial DNA is limited by mRNA-specific translational activation. Steele, D.F., Butler, C.A., Fox, T.D. Proc. Natl. Acad. Sci. U.S.A. (1996) [Pubmed]
  9. Genetic evidence that different functional domains of the PET54 gene product facilitate expression of the mitochondrial genes COX1 and COX3 in Saccharomyces cerevisiae. Valencik, M.L., McEwen, J.E. Mol. Cell. Biol. (1991) [Pubmed]
  10. COX3 mRNA-specific translational activator proteins are associated with the inner mitochondrial membrane in Saccharomyces cerevisiae. McMullin, T.W., Fox, T.D. J. Biol. Chem. (1993) [Pubmed]
  11. Suppression of carboxy-terminal truncations of the yeast mitochondrial mRNA-specific translational activator PET122 by mutations in two new genes, MRP17 and PET127. Haffter, P., Fox, T.D. Mol. Gen. Genet. (1992) [Pubmed]
  12. Rpm2, the protein subunit of mitochondrial RNase P in Saccharomyces cerevisiae, also has a role in the translation of mitochondrially encoded subunits of cytochrome c oxidase. Stribinskis, V., Gao, G.J., Ellis, S.R., Martin, N.C. Genetics (2001) [Pubmed]
  13. The YJR127C/ZMS1 gene product is involved in glycerol-based respiratory growth of the yeast Saccharomyces cerevisiae. Lu, L., Roberts, G.G., Oszust, C., Hudson, A.P. Curr. Genet. (2005) [Pubmed]
  14. Assembly of the mitochondrial membrane system. Characterization of the oxi2 transcript and localization of its promoter in Saccharomyces cerevisiae D273-10B. Thalenfeld, B.E., Hill, J., Tzagoloff, A. J. Biol. Chem. (1983) [Pubmed]
  15. Homologous maturase-like proteins are encoded within the group I introns in different mitochondrial genes specifying Yarrowia lipolytica cytochrome c oxidase subunit 3 and Saccharomyces cerevisiae apocytochrome b. Matsuoka, M., Matsubara, M., Kakehi, M., Imanaka, T. Curr. Genet. (1994) [Pubmed]
  16. A nuclear mutation that post-transcriptionally blocks accumulation of a yeast mitochondrial gene product can be suppressed by a mitochondrial gene rearrangement. Müller, P.P., Reif, M.K., Zonghou, S., Sengstag, C., Mason, T.L., Fox, T.D. J. Mol. Biol. (1984) [Pubmed]
  17. Interactions among COX1, COX2, and COX3 mRNA-specific translational activator proteins on the inner surface of the mitochondrial inner membrane of Saccharomyces cerevisiae. Naithani, S., Saracco, S.A., Butler, C.A., Fox, T.D. Mol. Biol. Cell (2003) [Pubmed]
  18. OXA1, a Saccharomyces cerevisiae nuclear gene whose sequence is conserved from prokaryotes to eukaryotes controls cytochrome oxidase biogenesis. Bonnefoy, N., Chalvet, F., Hamel, P., Slonimski, P.P., Dujardin, G. J. Mol. Biol. (1994) [Pubmed]
  19. Identification of a third nuclear protein-coding gene required specifically for posttranscriptional expression of the mitochondrial COX3 gene is Saccharomyces cerevisiae. Kloeckener-Gruissem, B., McEwen, J.E., Poyton, R.O. J. Bacteriol. (1988) [Pubmed]
  20. Characterization of mRNAs and coding potential of the PET54 gene from Saccharomyces cerevisiae. Burke, K.A., McEwen, J.E. Biochem. Int. (1991) [Pubmed]
  21. Elevated levels of petite formation in strains of Saccharomyces cerevisiae restored to respiratory competence. II. Organization of mitochondrial genomes in strains having high and moderate frequencies of petite mutant formation. Evans, R.J., Clark-Walker, G.D. Genetics (1985) [Pubmed]
  22. Expression of green fluorescent protein from a recoded gene inserted into Saccharomyces cerevisiae mitochondrial DNA. Cohen, J.S., Fox, T.D. Mitochondrion (2001) [Pubmed]
  23. Molecular cloning and nucleotide sequence of the nuclear PET122 gene required for expression of the mitochondrial COX3 gene in S. cerevisiae. Ohmen, J.D., Kloeckener-Gruissem, B., McEwen, J.E. Nucleic Acids Res. (1988) [Pubmed]
  24. Afg3p, a mitochondrial ATP-dependent metalloprotease, is involved in degradation of mitochondrially-encoded Cox1, Cox3, Cob, Su6, Su8 and Su9 subunits of the inner membrane complexes III, IV and V. Guzélin, E., Rep, M., Grivell, L.A. FEBS Lett. (1996) [Pubmed]
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