Regulation of Biosynthesis of Ribosomes

Abstract

INTRODUCTION
The ribosomes account for 40–50% of the cell mass of rapidly growing bacteria. It is therefore not surprising that the biosynthesis of ribosomes is a precisely regulated process requiring a strict coordination of the production of the 50–60 different molecules forming part of the ribosomal structures.

At our present stage of ignorance, we have limited information about the regulatory processes governing ribosome biosynthesis in prokaryotes:

Are all structural molecules of the ribosomes, RNA as well as proteins, regulated through one and the same basic mechanism?

Is the biosynthesis of rRNA regulated at the level of initiation of transcription, at the level of the substrates, or does a breakdown mechanism of the nascent rRNA play a role?

Is the biosynthesis of the ribosomal proteins regulated according to the Jacob-Monod model, or is there only an indirect control of the transcription frequency of the ribosomal protein operons through a common competition among all open promoters for the RNA polymerase molecules, as suggested by Maaløe (1969)?

Other questions might also be asked:

Does the regulatory mechanism primarily hit the ribosomal RNAs which in turn trigger the production of the ribosomal proteins? Inversely, are the ribosomal protein operons the prime target for the regulation, and do these proteins, or at least one of them, turn on the production of rRNAs?

Are the ribosomal proteins protecting the nascent rRNAs against degradation, leaving excess rRNA chains at the prey of nucleases?

The coordination between the rRNAs and the ribosomal proteins is a focal...