Ribosome production during recovery from puromycin treatment: Influence of 5-fluorouracil

Abstract

1. 1. Incubation of Escherichia coli 15T − with 5-fluorouracil prevents formation of normal 50-S ribosome particles. The “ribosomal RNA” produced in the presence of 5-fluorouracil has sedimentation characteristics similar to the normal 23-S and 16-S RNA; however, the amount of the component corresponding to 23-S RNA, when compared with 16-S RNA is much lower than normal. 2. 2. Simultaneous treatment of E. coli with puromycin and 5-fluorouracil allows accumulation of RNA having sedimentation characteristics similar to ribosomal RNA, and again the component corresponding to 23-S RNA is produced to a lesser extent than 16-S RNA. During recovery from treatment with puromycin and 5-fluorouracil, particles are formed; however, the component corresponding to the 50-S ribosomes appears lighter than normal in the sucrose gradient (and total ribosome formation is greatly inhibited). 3. 3. If RNA is allowed to accumulate in the presence of puromycin and the cells allowed to recover following removal of puromycin, there is a shift of the ribosomal RNA into newly formed ribosome particles and a preferential synthesis of structural ribosomal protein. The presence of 5-fluorouracil in the medium does not prevent or reduce formation of ribosomes or the preferential synthesis of ribosomal protein. If puromycin RNA accumulates in the presence of 5-fluorouracil preferential synthesis of ribosomal protein does not occur during recovery in fresh medium.