Transcriptional Units for Ribosomal Proteins in Yeast

Abstract

The effects of UV irradiation on the rates of synthesis of individual ribosomal proteins in yeast [Saccharomyces carlsbergensis] were examined and compared with the UV sensitivities of the synthesis of other yeast proteins. The synthesis of yeast ribosomal proteins is much more sensitive to UV irradiation than that of other yeast cellular proteins. Taking into account the half-life of yeast mRNA, the results indicate that the genes coding for ribosomal proteins form part of long transcriptional units, which are much longer than the DNA stretch needed to code for a ribosomal protein of average molecular weight. Saturation hybridization of total poly(A)-containing mRNA with yeast nuclear DNA revealed that as much as 30% of DNA is complementary to yeast mRNA. Thus, the primary transcript of a protein gene on the average is about 1.7 times the length of the actual messenger. The clustering of the yeast ribosomal protein genes in a number of common transcriptional units was suggested.