HEAT-SHOCK PROTEIN HSP60 CAN ALLEVIATE THE PHENOTYPE OF MITOCHONDRIALRNA-DEFICIENT TEMPERATURE-SENSITIVE MNA2 PET MUTANTS

mna2, which belongs to the class I temperature-sensitive pet mutants t hat lose mitochondrial (mt)RNA at restrictive temperature, was shown b y complementation and sequence determination to correspond to the gene coding for HSP60. Both mna2-1 and mna2-2, the two available alleles o f mna2, have conservative single amino acid substitutions in the HSP60 gene. Valine substitutes for an alanine (position 47) in mna2-1, and an isoleucine substitutes for a valine (position 77) in mna2-2. These substitutions result in defects in respiration and in steady-state mtR NA accumulation. Wild-type hsp60 alleviates the mtRNA phenotype comple tely, while partially relieving the respiratory deficiency.