Mitochondrial Translation Products in Nuclear Respiration-deficient pet Mutants of Saccharomyces cerevisiae

Abstract

The biogenesis of functional mitochondria involves the cooperation of two genetic systems, those of the nucleus and the mitochondrial genome. In yeast, the mitochondrial genome contributes only about 10% to the mitochondrial protein mass. With its limited information content, mtDNA represents a relatively simple genetic system, which has been studied extensively in the past. Thus, its genetic organization and its DNA sequence are now largely known (for review, see Borst and Grivell 1978; Kroon and Saccone 1980). On the other hand, much more information is needed, at the molecular level, about the contribution of the nuclear genome to the formation of intact mitochondria. Similarly, any possible nuclear-mitochondrial interactions specifically controlling the biosynthesis of mitochondrial protein components also await a detailed characterization. To initiate a systematic biochemical and genetic approach to these questions, a large number of nuclear respiratory-deficient Saccharomyces cerevisiae mutants have been isolated and genetically characterized by one of us (E.S.) during the past several years. To avoid secondary transitions of these pet mutants into the cytoplasmic ρ⁻ genotype, which is often observed with nonconditional pet mutants, a special screening for temperature-sensitive lactate utilization was performed with 22°C as the permissive temperature and 36°C as the nonpermissive temperature (Schweizer et al. 1977). This temperature-sensitive phenotype distinguishes the nuclear pet mutants described in this paper from those previously studied in other laboratories (Sherman and Slonimski 1964; Ebner et al. 1973a,b; Tzagoloff et al. 1975). Between 200 and 300 different complementation groups have been characterized so far by systematically crossing about...