Ribosomal protein biosynthesis during starvation and refeeding in Tetrahymena pyriformis

Abstract

The relative abundance of translationally active mRNAs for ribosomal proteins has been measured using Tetrahymena pyriformis subjected to refeeding after a 20-h starvation period. The level of ribosomal proteins synthesized, using total RNA from starved cells and a wheat germ extract for translation, corresponded to less than 3% of the total [ 35S]methionine incorporated into protein. In contrast, total RNA isolated from cells after 1 to 3 h of refeeding yielded a two- to eightfold increase in the amount of the individual ribosomal proteins synthesized, with the maximum level occurring at about 2 h following refeeding. In addition to the increase in the proportion of ribosomal proteins synthesized in vitro, there was also a near linear increase with time in the translational activity of RNA isolated from refed cells. Approximately 25 proteins synthesized in vitro comigrated with authentic ribosomal proteins, as determined by two-dimensional gel electrophoresis. It appears likely that the control of ribosomal protein synthesis in Tetrahymena subjected to starvation and refeeding occurs at the level of transcription.