Nucleo-mitochondrial interactions in Saccharomyces cerevisiae: characterisation of a nuclear gene suppressing a defect in mitochondrial tRNAAsp processing.

We utilized the heat-sensitive mutant strain (Ts932), bearing a mutation at position 61 in the mitochondrial tRNAAsp gene, to identify nuclear genes involved in tRNA biogenesis; this mutant is defective in 30-end processing and consequently in the production of mature mitochondrial tRNAAsp. We transformed this strain with a yeast nuclear library and we isolated among other suppressors, an unknown, nonessential gene (called SMM1, corresponding to open reading frame YNR015w), which restored the growth on glycerol and a normal amount of processed tRNAAsp in the mutant. The gene contains a domain highly conserved in evolution from bacteria to human and its product has been recently shown to have dihydrouridine synthase activity.