The molecular basis of emetine resistance in chinese hamster ovary cells: Alteration in the 40S ribosomal subunit

The molecular basis of resistance to the protein synthesis inhibitor emetine has been examined in cell-free, protein-synthesizing extracts derived from normal and emetine-resistant (Emt^R) mutants. We had earlier shown that protein synthesis in extracts of the mutant cells was resistant to the inhibitory action of the emetin. When extracts from a wild-type and mutant cell line were fractionated into supernatant (S-100) and polyribosome fractions and mixed in different combinations, resistance to emetine was found to be associated with the mutant polyribosome fraction. Further fractionation of wild-type and mutant polyribosomes into 40S and 60S ribosomal subunits and mixing them in various combinations with an S-100 fraction from the wild-type cell indicates that resistance of mutant cells to emetine involves an alteration in the 40S ribosomal subunit.The behavior of Emt^R has also been examined in somatic cell hybrids. Studies of Emt^R × Emt^S hybrid cell lines in vivo and in vitro show that Emt^R is phenotypically recessive to Emt^S, which is consistent with the ribosomal location of the genetic change.