Regulation of mitochondrial DNA transcription by protein post‐translational modifications

Abstract

Mammalian cells contain genetic information in two compartments, the nucleus and the mitochondria. Mitochondrial DNA (mtDNA) encodes thirteen protein subunits required for oxidative phosphorylation. The remaining mitochondrial proteome, including additional oxidative phosphorylation subunits, and the proteins necessary for mtDNA replication, expression, and stability, is encoded by the nuclear genome. Therefore, to respond to metabolic changes, mitochondrial gene expression must be coordinated with nuclear gene expression. While the control of nuclear gene expression is widely studied, there is a need to understand the regulation of mtDNA transcription. Our central hypothesis is that reversible post‐translational modification of the mtDNA transcriptional machinery is a means to tune mtDNA transcription in response to changes in cellular metabolism. Here, using in vitro biochemical and cell biology approaches, we describe the effects of lysine acetylation and serine/threonine/tyrosine phosphorylation on the mtDNA binding ability and transcriptional activity of three proteins, mitochondrial transcription factor B2 (TFB2M), the mitochondrial polymerase (POLRMT), and mitochondrial ribosomal protein L12 (MRPL12). Our in vitro biochemical results indicate that phosphorylation of TFB2M may impede mtDNA binding and subsequently alter transcription initiation. Modification of MRPL12 may alter the ability of MRPL12 to bind and stabilize POLRMT. We also report a temporal response in the transcript level of mitochondrial and nuclear genes in response to cell growth conditions used to drive a dependence on mitochondrial metabolism. Importantly, mtDNA content is unchanged in these conditions, providing evidence for a regulated transcriptional response of the mitochondrial genome. It is expected that these findings will lead to a more complete understanding of the dynamics and coordination of mitochondrial and nuclear gene transcription, as well as adding to the understanding of the importance of protein post‐translational modifications in regulating aspects of mitochondrial function.Support or Funding InformationThis material is based upon work supported by the National Science Foundation Division of Molecular and Cellular Biosciences under Grant No. 1814845.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.