Mitochondrial and nuclear mitoribosomal suppressors that enable misreading of ochre codons in yeast mitochondria

Publisher Website
Google Scholar
Abstract
A systematic search for suppressors of mutations which cause a deficiency in the splicing of mitochondrial RNA has been undertaken. These splicing mutations were localized in the mRNA-maturase coding sequence of the second intron of the cob-boxgene, i.e. in the box3locus. A total of 953 revertants (mostly spontaneous in origin) were isolated and their genetic nature (nuclear vs. mitochondrial) and phenotype characterized. Most revertants were mitochondrially determined and displayed a wild-type phenotype. A mitochondrial suppressor unlinked with the box3 −target mutation was uncovered among the revertants displaying a pseudo-wild phenotype: out of 26 revertants analyzed, derived from 7 different box3− mutants only one such suppressor mutation mim3-1 was found. It was localized by rho− deletion mapping in the region between the oxi2 and oxi3 gene, within (or in the vicinity) the gene specifying the 15S ribosomal RNA. Nuclear suppressors were isolated from seven different box3 −mutants. All were recessive and had a pseudo-wild phenotype. Three such suppressors nam3-1, nam3-2 and nam3-3 were investigated more extensively. Tetrad analysis has shown that they are alleles of the same nuclear locus NAM3 and mitotic analysis has shown that they do not segregate mitotically.