Characterization of a yeast nuclear gene, AEP2, required for accumulation of mitochondrial mRNA encoding subunit 9 of the ATP synthase

The temperature-conditional pet mutant, ts379, of Saccharomyces cerevisiae fails to synthesize mitochondrial ATP synthase subunit 9 at the restrictive temperature due to mutation of a single nuclear locus, AEP2. The inability to synthesize subunit 9 correlates with a lowered accumulation of the cognate oli1 mRNA indicating that the AEP2 product is involved in oli1 transcript maturation or stabilization. The AEP2 gene has been isolated in this study from a wild-type yeast genomic library by genetic complementation of ts379 at the restrictive temperature. A 1,740 nucleotide open-reading frame was observed that encodes a basic, hydrophilic protein of 67,534 Da which possesses a putative mitochondrial address signal. Disruption of chromosomal DNA within this reading frame produced a non-conditional respiratory mutant unable to synthesize subunit 9, identifying the AEP2 gene. Hybridization analyses indicate that AEP2 is located on chromosome XIII and produces a 2.1 kb poly(A)+ transcript. Two additional open-reading frames were found in close proximity to that of AEP2. The three open-reading frames shared no significant homology with entries in several data bases.