PET112, A SACCHAROMYCES-CEREVISIAE NUCLEAR GENE REQUIRED TO MAINTAIN RHO(-DNA() MITOCHONDRIAL)

The nuclear gene PET112 was originally identified by a mutation (pet11 2-1) that specifically blocked accumulation of cytochrome c oxidase su bunit II. The mutation causes a post-transcriptional defect since the level of COX2 mRNA in the mutant is the same as in the wildtype. Howev er, PET112 does not have a function similar to that of PET111, a COX2 mRNA-specific translational activator: while pet111 mutations are supp ressed by chimeric COX2 mRNAs bearing 5'leaders of other mitochondrial mRNAs, pet112-1 is not. The PET112 gene was isolated and shown to cod e a protein of 541 residues (62 kDa) with no significant homology to k nown amino-acid sequences. By hybridization to defined genomic clones the gene was mapped to chromosome II between cdc25 and ilsl. Disruptio n of the PET112 open reading frame destabilized the mitochondrial geno me, causing cells to become rho(-). This finding suggests that PET112 has an important general function in mitochondrial gene expression, pr obably in translation.