A mouse leukemia cell mutant resistant to blasticidin s

Abstract

After nitrosoguanidine mutagenesis we isolated from mouse leukemia L5178Y cells a mutant cell (Bla‐R) resistant to blasticidin S, an inhibitor of protein synthesis. Neither growth nor leucine incorporation into hot‐acid insoluble fraction of Bla‐R cell was inhibited by 5 to 20 μg/ml blasticidin S, which almost completely blocked protein synthesis as well as growth of the parental L5178Y cells. However, other inhibitors such as fusidic acid, cycloheximide, ricin D or L‐asparaginase blocked protein synthesis in Bla‐R cells to the same extent as in L5178Y cells. Protein synthesis in vitro using S‐30 extracts from the parental cell line L5178Y was almost completely blocked in the presence of the antibiotic, while no inhibition by blasticidin S occurred when S‐30 extracts from Bla‐R mutant cells were used. Protein synthesis assays were made by using the S100 fraction from rat liver together with ribosomes from either L5178Y cells or Bla‐R cells. Blasticidin S inhibited protein synthesis when ribosomes were derived from L5178Y cells, but not from Bla‐R mutant.