Biochemical and genetic evidence for a new class of emetine-resistant Chinese hamster cells with alterations in the protein biosynthetic machinery.

We have isolated a number of emetine-resistant mutants from several different clones of CHO and CHL cells. Protein synthesis in extracts derived from each of the mutants is much more resistant to emetine than in the parental, emetine-sensitive cell lines, indicating the lesions affect the protein synthetic machinery directly. However, hybrid cell lines, derived from fusing either of two different emetine-resistant CHO mutants with either one of two different emetine-resistant CHL cells, are much more sensitive to growth inhibition by emetine than either parent. In addition, the incorporation of [3H] amino acids into protein in vivo and protein synthesis in vitro in extracts derived from these hybrids is much more sensitive to emetine inhibition than in either emetine-resistant parent. In contrast, no complementation was observed in hybrids derived from fusing two emetine-resistant CHO mutants or in hybrids derived from fusing two emetine-resistant CHL cell lines. These results indicate the CHO emetine-resistant mutants belong to one complementation group and the CHL emetine-resistant mutants belong to another. The genetic loci represented by these two complementation groups must both encode for gene products involved in protein synthesis.