Mitochondrial suppression of a yeast nuclear mutation which affects the translation of the mitochondrial apocytochrome b transcript.

We describe a mitochondrial suppressor mutation, which restores respiratory competence to the nuclear pet- -mutant MK2. This mutant lacks the message of the mitochondrial cob-gene and instead accumulates a partially spliced pre-mRNA which is not translated. Complete processing and translation of the cob-RNA is restored by a rearrangement of the mitochondrial DNA, leading to a fusion of the cob-coding sequences with the leader of oli1, the mitochondrial gene coding for subunit IX of the ATPase. We conclude that the nuclear gene affected in MK2 is essential to allow translation of transcripts which contain the cob-leader sequence.