A single mutation in the 15S rRNA gene confers nonsense suppressor activity and interacts with mRF1 the release factor in yeast mitochondria

A single mutation in the 15S rRNA gene confers nonsense suppressor activity and interacts with mRF1 the release factor in yeast mitochondria

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We have determined the lycogel nucleotide sequence of the mim3-1 mitochondrial ribosomal suppressor, acting on ochre mitochondrial mutations and one frameshift mutation in Saccharomyces cerevisiae.The 15s rRNA suppressor gene contains a G633 to C transversion.Yeast mitochondrial G633 corresponds to G517 of the E.

coli 15S rRNA, which is occupied by an invariant G in all known small rRNA sequences.Interestingly, this mutation has occurred at the same position as the known MSU1 mitochondrial suppressor which changes G633 to A.The suppressor mutation lies in a highly conserved region of the rRNA, known in E.

coli as the 530-loop, interacting with the S4, S5 and S12 ribosomal proteins.We also show an interesting interaction between the mitochondrial mim3-1 and the nuclear nam3-1 suppressors, both of which have the same action spectrum on mitochondrial mutations: nam3-1 abolishes the suppressor effect when present with mim3-1 in the same haploid cell.We discuss these results in the light of the nature of Nam3, identified by [1] as the yeast mitochondrial translation release factor.

A hypothetical mechanism of suppression by "ribosome shifting" is also discussed amina muaddi scarpe trasparenti in view of the nature of mutations suppressed and not suppressed.