Cytoplasmic and Nuclear Inheritance of Erythromycin Resistance in Human Cells

Abstract

The biogenesis of mitochondria depends on the cooperation of the nuclear and mitochondrial genomes (Schatz and Mason 1974; Borst and Grivell 1978). The striking nature of the interaction between these two distinct genetic systems is seen in the assembly of the mitochondrial protein-synthesizing apparatus and the respiratory-enzyme complexes of the inner mitochondrial membrane. Mitochondrial protein synthesis is specifically inhibited by a number of antibiotics, and the characterization of mitochondrially inherited mutants resistant to these inhibitors has proved useful in elucidating the genetic function of the mitochondrial genome in lower eukaryotes (Borst and Grivell 1978; Tzagoloff et al. 1979). Cytoplasmically inherited and presumably mitochondrially encoded mutants resistant to chloramphenicol (Wallace et al. 1975; Mitchell and Attardi 1978; Munro et al. 1978) and erythromycin (Doersen and Stanbridge 1979), as well as mutants deficient in mitochondrial protein synthesis (Wiseman and Attardi 1979), have been described in human cell lines.

We found that the growth of human HeLa cells in culture was inhibited by erythromycin. A cytoplasmically inherited erythromycin-resistant mutant, ERY2301, was isolated following the mutagenic treatment of sensitive cells (Doersen and Stanbridge 1979). Recently, we have characterized two additional mutants, ERY2305 and ERY2309, which represent a new class of erythromycin-resistant mutants in human cells. These mutants have growth characteristics that are remarkably similar to those of ERY2301, but they are nuclearly encoded (C. Doersen and E. Stanbridge, in prep.).

Assays of cell-free protein synthesis demonstrated that erythromycin is effective in inhibiting the protein-synthesizing activity of HeLa mitochondria (Table 1). Mitochondria isolated from all...