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

The Saccharomyces cerevisiae nuclear gene OXA1, which is conserved from pro karyotes to human, was shown to be essential for cytochrome c oxidase and F 1F0-ATP synthase biogenesis. We have searched for an orthologue of OXA1 in Schizosaccharomyces pombe, another yeast that is highly diverged from S. ce revisiae and which could more closely model higher eukaryotes. In particula r, S. pombe exhibits a limited growth under anaerobic conditions and is pet ite negative, that is it does not tolerate large deletions of its mitochond rial DNA. Surprisingly, two S. pombe cDNAs able to complement an S. cerevis iae oxa1 mutation were isolated. The corresponding genes have different chr omosomal locations and intron contents. They encode distinct proteins, both sharing a weak sequence identity one with the other and with Oxa1p. A phen otypic analysis of both single inactivations demonstrates that only one gen e is essential for respiration in S. pombe. However, the double inactivatio n is lethal. This work gives new insight into the dependence of S. pombe vi ability upon oxa1 function, providing evidence of a connection between peti te negativity, a functional respiratory chain and F1F0-ATP synthase complex in S. pombe.