Abstract
Cell survival requires the control of biomolecule concentration, i.e. they should approach homeostasis. With informative macromolecules, the particular concentration variation ranges depend on each type: DNA is not buffered, but mRNAs and proteins are homeostatically controlled, which leads to the ribostasis and proteostasis concepts. In recent years, in order to understand the particular features of mRNA ribostasis and proteostasis, we have studied variations in mRNA and protein concentrations in different situations in the model organism S. cerevisiae. Here we extend this study by comparing published data from three other model organisms: E. coli, S. pombe and cultured human cells. We describe that mRNA ribostasis is less strict than proteostasis, but seems tightly controlled. A constant ratio appears between the average decay and dilution rates during the cell growth for mRNA, but not for proteins. We postulate that this is due to a trade-off between the cost of synthesis and the response capacity at the transcription level that is not possible at the translation level because the high stability of proteins, compared to that of mRNAs, precludes it. We hypothesize that the middle-place role of mRNA in the Central Dogma of Molecular Biology and its chemical instability make it more suitable than proteins for the fast changes needed for gene regulation.