Szatkowska, R.; Furmanek, E.; Kierzek, A.M.; Ludwig, C.; Adamczyk, M. Mitochondrial Metabolism in the Spotlight: Maintaining Balanced RNAP III Activity Ensures Cellular Homeostasis. Int. J. Mol. Sci.2023, 24, 14763.
Szatkowska, R.; Furmanek, E.; Kierzek, A.M.; Ludwig, C.; Adamczyk, M. Mitochondrial Metabolism in the Spotlight: Maintaining Balanced RNAP III Activity Ensures Cellular Homeostasis. Int. J. Mol. Sci. 2023, 24, 14763.
Szatkowska, R.; Furmanek, E.; Kierzek, A.M.; Ludwig, C.; Adamczyk, M. Mitochondrial Metabolism in the Spotlight: Maintaining Balanced RNAP III Activity Ensures Cellular Homeostasis. Int. J. Mol. Sci.2023, 24, 14763.
Szatkowska, R.; Furmanek, E.; Kierzek, A.M.; Ludwig, C.; Adamczyk, M. Mitochondrial Metabolism in the Spotlight: Maintaining Balanced RNAP III Activity Ensures Cellular Homeostasis. Int. J. Mol. Sci. 2023, 24, 14763.
Abstract
RNA polymerase III (RNAP III) holoenzyme activity and its products processing have been linked to several metabolic dysfunction in lower and in higher eukaryotes. Alterations in the activity of RNAP III driven synthesis of non-coding RNA, causes extensive changes in the glucose metabo-lism. Increased RNAP III activity in S.cerevisiae maf1Δ strain, manifests with lethality when grown on non-fermentable carbon source. This lethal phenotype is suppressed by reducing tRNA syn-thesis. The cause for the lack of growth neither the underlying molecular mechanism has not been deciphered and has been awaiting a scientific explanation for a decade. Our previous proteomics data suggested mitochondrial dysfunction of the strain. Using model mutant strains maf1Δ (with increased tRNA abundance) and rpc128-1007 (with reduced tRNA abundance) we collected data showing major changes in TCA cycle metabolism of the mutants that explain the phenotypic ob-servations.
The present study, based on 13C flux data and analysis of TCA enzymes activities, identifies the flux constraints in the mitochondrial metabolic network. The lack of growth is associated with the de-crease in TCA cycle activity and downregulation of the flux towards glutamate, aspartate and phosphoenolopyruvate (PEP), the metabolic intermediate feeding gluconeogenic pathway. rpc128-1007, the strain that is unable to increase tRNA synthesis due to a mutation in C128 subunit, has increased activity of TCA cycle under non-fermentable conditions.
To summarize, cells with non-optimal activity of RNAP III, undergo substantial adaptation to a new metabolic state, that make them vulnerable under specific growth conditions. Our results strongly suggest that balanced, non-coding RNA synthesis that is coupled to glucose signaling is a fundamental requirement to sustain cell’s intracellular homeostasis and flexibility under changing growth conditions. Presented results provide insight into the possible role of RNAP III in mito-chondrial metabolism of other cell types.
Keywords
RNA Polymerase III, RNAP III, TCA cycle, mitochondrial metabolism, MAF1, 13C flux, systems biology, growth rate
Subject
Biology and Life Sciences, Biochemistry and Molecular Biology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
