The SUV3 gene from Saccharomyces douglasii is a functional equivalent of its Saccharomyces cerevisiae orthologue and is essential for respiratory growth.

Abstract

In the yeast Saccharomyces cerevisiae the product of the nuclear gene SUV3 has been shown to be involved in a variety of mitochondrial post-transcriptional processes. We have cloned and sequenced the SUV3 gene from Saccharomyces douglasii, a close relative of S. cerevisiae which has important changes in the organization of its mitochondrial genome and concomitant changes in nucleo-mitochondrial interactions. We show that the S. douglasii SUV3 gene shares considerable structural homology (92% amino acid sequence identity) with its S. cerevisiae counterpart and that their nucleotide sequences display evidence of recent divergence. To determine the function of the S. douglasii SUV3 gene we have constructed a strain carrying an inactive SUV3 gene and analyzed the effect of this inactivation on the integrity of the mitochondrial genome and on the stability of mitochondrial transcripts. We have demonstrated that the S. douglasii SUV3 gene, like the S. cerevisiae gene, is essential for respiratory growth and for stability of the intron-containing mitochondrial transcripts, thus the two genes are functionally equivalent. Also the S. douglasii and S. cerevisiae SUV3 genes are completely interchangeable, despite the differences in the structure of the mitochondrial chromosome in the two yeasts.