Ribosome regulatory mechanisms

During early development, when cell divisions are occurring rapidly, demand for certain products associated with the translation apparatus (ribosomes) increases. Special regulatory mechanisms ensure that these gene products are produced in the required amounts and that they are not overproduced in the more mature organism. 

Gene amplification production of extrachromo-somal copies of the genes for ribosomal RNA. In frog s egg cells G.a. leads to the formation of numerous extrachromosomal nucleoli. G.a. is thus a special regulatory mechanism for RNA. It is not the same as Redundancy (see), which is the presence of multiple copies of the same gene on the chromosome. 

Regulatory mechanisms at the level of mRNA translation could also lead to gross metabolic changes. The mechanism of protein synthesis has been exhaustively studied [5], and many components have been implicated. Changes in each of these components—ribosomes, factors involved in the ribosomal binding of mRNA, in the initiation and termination of protein synthesis, and in polypeptide chain elongation, tRNA, and the components responsible for its acylation and subsequent transfer to the polysomal complex—could potentially lead to alteration in the rate, extent, or fidelity of protein synthesis. 

Figure 1 Generalized model for sensing regulatory effectors by nascent mRNA leader transcripts. Transcription attenuation mechanisms have been identified in which the nascent transcript interacts with a translating 70S ribosome, a protein, an RNA molecule or a small metabolite, (a) Binding of the effector molecule promotes transcription termination, (b) Binding of the effector molecule promotes transcription readthrough (antitermination). See text for details.

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