Fig. 6. Mss51p acts through the COX1 coding sequence to promote COX1 translation. (A) Schematic representation of the chimeric COX1 gene present in the plasmid pXPM42. The COX1(1–512)::ARG8^m gene (represented as open boxes) was fused to 310 bp of the COX2 5′-UTL and 270 bp of the COX2 3′-UTR. The 54 bp from the COX2 promoter and 75 bp from the COX2 mRNA 3′ end are represented by thick lines. The black triangle indicates the position of the pre-Arg8p targeting signal cleavage site. (B) Expression of the chimeric COX1(1–512)::ARG8^m gene in mss51Δ and pet309Δ mutants. Synthetic ρ^–, haploid strains carrying pXPM42 DNA were patched in vertical stripes on YPD. Cells containing wild-type ρ⁺ mitochondria were patched on YPD on horizontal stripes. Their relevant genotypes are as indicated. The stripes were cross-printed on YPD and allowed to mate overnight before being replicated to glucose minimal medium lacking arginine (–Arg) and complete non-fermentable ethanol/glycerol medium (YPEG). These plates were incubated for 5 days at 30°C to reveal the phenotype of the resulting heteroplasmic diploid strains. Strain details are given in the Supplementary data.