11 Forging the Factory: Ribosome Synthesis and Growth Control in Budding Yeast

Abstract

The observation that the level of RNA in a culture of Escherichia coli is related to the growth rate originated the study of macromolecular regulation (for review, see Maaloe and Kjeldgaard 1966). As the role of the ribosome in translation became evident, the issue could be clearly framed: Since the rate of growth depends on the synthesis of proteins, and the synthesis of proteins depends on ribosomes, the regulation of growth must ultimately depend on the regulation of synthesis of new ribosomes, which consumes a large fraction of the cell’s resources. This is undoubtedly as true of eukaryotic cells as of prokaryotic cells. This chapter deals largely with the regulation of ribosome synthesis in budding yeast. Aspects of the regulation of ribosomal RNA and of ribosomal protein (RP) synthesis in metazoan cells are covered in Chapters 12 and 9, respectively. At the outset, a short detour into the regulation of ribosome synthesis in E. coli can serve as a useful introduction to the problem. More than 20 years ago, it became clear from the work of Nomura, Lindahl, and others that the synthesis of RPs in E. coli is regulated by an extraordinary example of tight inventory control. Although the transcription of mRNA encoding RPs is more or less constitutive, the translation of RP messenger RNAs (mRNAs) depends on the continued formation of new rRNA with which the new RPs can associate. If there is insufficient transcription of new rRNA, the free RPs bind specifically to their (usually polycistronic) mRNAs...