Regulation of ribosome synthesis in Tetrahymena pyriformis. 2. Coordination of synthesis of ribosomal proteins and ribosomal RNA during nutritional shift-up.
The addition of nutrients to long-time-starved cells of Tetrahymena pyriformis leads to a 50-60-fold increase in the rate of synthesis of ribosomal proteins (r-proteins). This is achieved by a 6-fold increase in the relative rate of r-protein synthesis and a 8-10-fold increase in the rate of total protein synthesis. Synthesis of r-proteins constitutes one third of total cellular protein synthesis 2-4 h after refeeding and the absolute rate of r-protein synthesis is approximately three-times greater than in exponentially growing cells. The synthesis of the individual r-proteins is coordinately regulated during a nutritional shift-up, and de novo synthesized r-proteins are stable. Addition of actinomycin D prevents the increase in the rate of r-protein synthesis. The rates of synthesis of rRNA and r-protein increase in concert, implying coordinate regulation. Furthermore, a comparison of the observed accumulation of r-proteins with the predicted accumulation based on the accumulation of rRNA suggests that rRNA and r-protein are synthesized in a stoichiometrically balanced way during the entire refeeding period.
D000818:Animals; D003470:Culture Media / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D007700:Kinetics; D011132:Polyribosomes / Q000378:metabolism; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D012269:Ribosomal Proteins / Q000096:biosynthesis*; D012270:Ribosomes / Q000378:metabolism*; D013769:Tetrahymena pyriformis / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure
D003470:Culture Media; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; D003609:Dactinomycin