Coordinate regulation of the synthesis of eukaryotic ribosomal proteins.

We have developed a method of r the direct measurement, in eukaryotic cells, of the synthesis of ribosomal proteins, irrespective of the synthesis of ribosomes. In this way the synthesis of ribosomal proteins has been examined in mutant strains of Saccharomyces cerevisiae, which are unable to synthesize ribosomes under nonpermissive conditions. The results suggest that the synthesis of more than 40 ribosomal proteins is under coordinate control. Under nonpermissive conditions,the synthesis of each h protein declines exponentially to a basal level which is 10-20% fo normal. The kinetics of that decline suggest that an early, if not primary, result of the nonpermissive conditions is the cessation of production of new mRNA for eac of the ribosomal proteins. The coordinate regulation appears not to be influenced directly by the rate of transcription of ribosomal precursor RNA.