Analysis of rho mutability in Saccharomyces cerevisiae. I. Effects of mmc and pet-ts alleles.

Two additional types of nuclear determinants involved in the control of spontaneous mutability of rho in S. cerevisiae have been identified: mmc and the pet-ts 1, 2, 10, 52 and 53 genes. These genes in their mutated recessive form increase at various extents the number of respiratory deficient cytoplasmic "petite" mutants accumulated. The gene mmc does not affect the respiratory activity and is not temperature-dependent whereas the pet-ts genes determine at the non permissive temperature a respiratory deficient phenotypes even if they affect the mutability of rho at the permissive and at the non permissive temperature. The data here reported suggest that a "replicative complex" exists for the mitochondrial DNA. It is in the purpose of this paper to deal with the relative contribution that mmc and pet-ts gene products have in ensuring the fidelity of this "replicative complex".