Cell volume homeostatically controls the rDNA repeat copy number and rRNA synthesis rate in yeast

Abstract

The adjustment of transcription and translation rates to variable needs is of utmost importance for the fitness and survival of living cells. We have previously shown that the global transcription rate for RNA polymerase II is regulated differently in cells presenting symmetrical or asymmetrical cell division. The budding yeast Saccharomyces cerevisiae adopts a particular strategy to avoid that the smaller daughter cells increase their total mRNA concentration with every generation. The global mRNA synthesis rate lowers with a growing cell volume, but global mRNA stability increases. In this paper, we address what the solution is to the same theoretical problem for the RNA polymerase I synthesis rate. We find that the RNA polymerase I synthesis rate strictly depends on the copy number of its 35S rRNA gene. For cells with larger cell sizes, such as a mutant cln3 strain, the rDNA repeat copy number is increased by a mechanism based on a feed-back mechanism in which Sir2 histone deacetylase homeostatically controls the amplification of the rRNA genes at the rDNA locus in a volume-dependent manner.

Dynamic analysis of sequestration-based feedbacks in cellular and biomolecular circuits

“…Other examples of sequestration-based feedback include biomolecular circuits involved in controlling rDNA repeats [34] and the growing evidence of feedback between specific microRNAs and TFs. In the latter example, TFs activate the synthesis of microRNAs and the feedback is implemented by having the microRNA bind and sequester the TF mRNA to turn off TF synthesis [35], [36].…”