The respiratory gene OXA1 has two fission yeast orthologues which together encode a function essential for cellular viability.

The Saccharomyces cerevisiae nuclear gene OXA1, which is conserved from prokaryotes to human, was shown to be essential for cytochrome c oxidase and F1F0-ATP synthase biogenesis. We have searched for an orthologue of OXA1 in Schizosaccharomyces pombe, another yeast that is highly diverged from S. cerevisiae and which could more closely model higher eukaryotes.

Large-scale phenotypic analysis--the pilot project on yeast chromosome III.

In 1993, a pilot project for the functional analysis of newly discovered open reading frames, presumably coding for proteins, from yeast chromosome III was launched by the European Community. In the frame of this programme, we have developed a large-scale screening for the identification of gene/protein functions via systematic phenotypic analysis. To this end, some 80 haploid mutant yeast strains were constructed, each carrying a targeted deletion of a single gene obtained by HIS3 or TRP1 transplacement in the W303 background and a panel of some 100 growth conditions was established, ranging from growth substrates, stress to, predominantly, specific inhibitors and drugs acting on various cellular processes.

PetCR46, a gene which is essential for respiration and integrity of the mitochondrial genome.

In the frame of the European Pilot Project for the functional analysis of newly discovered open reading frames (ORFs) from Saccharomyces cerevisiae chromosome III, we have deleted entirely the YCR46C ORF by a one-step polymerase chain reaction method and replaced it by the HIS3 marker in the strain W303. The deletion has been checked by meiotic segregation and Southern blot analyses. Characterization of the deleted strain indicates that YCR46C is essential for respiration and maintenance of the mitochondrial genome since its deletion leads to the appearance of 100% of cytoplasmic petites.

Heat shock protein HSP60 can alleviate the phenotype of mitochondrial RNA-deficient temperature-sensitive mna2 pet mutants.

mna2, which belongs to the class I temperature-sensitive pet mutants that lose mitochondrial (mt)RNA at restrictive temperature, was shown by complementation and sequence determination to correspond to the gene coding for HSP60. Both mna2-1 and mna2-2, the two available alleles of mna2, have conservative single amino acid substitutions in the HSP60 gene. Valine substitutes for an alanine (position 47) in mna2-1, and an isoleucine substitutes for a valine (position 77) in mna2-2.

Cloning of a human gene involved in cytochrome oxidase assembly by functional complementation of an oxa1- mutation in Saccharomyces cerevisiae.

The yeast nuclear gene OXA1 is essential for cytochrome oxidase assembly, so that a null mutation in the OXA1 gene leads to complete respiratory deficiency. We have cloned by genetic selection a human OXA1 (OXA1Hs) cDNA that complements the respiratory defect of yeast oxa1 mutants. The deduced sequence of the human protein shares 33% identity with the yeast OXA1 protein.