Regulation of Mitochondrial DNA Transcription by Post‐Translational Modifications of Mitochondrial Transcription Factor B2

Abstract

Mitochondrial DNA (mtDNA) encodes for 13 protein components required for oxidative phosphorylation (OXPHOS), the primary cellular energy production pathway. While the critical roles of mitochondria in metabolism and cellular function are well established, the mechanisms regulating expression of mtDNA‐encoded genes are poorly understood. Defects in the regulation of mtDNA transcription are implicated in numerous pathologies such as neurodegenerative disorders and cancers. mtDNA is complexed to proteins in structures known as nucleoids, of which some proteins play critical roles in transcriptional regulation. Our objective is to determine whether reversible post‐translational modifications (PTMs) of nucleoid proteins, including lysine acetylation and serine/threonine/tyrosine phosphorylation, regulate mtDNA transcription. Our central hypothesis is that PTMs alter the function of these proteins and provide a means of regulating mitochondrial gene expression. We highlight our work on the characterization of mitochondrial transcription factor B2 (TFB2M), focusing on the mutagenesis, bacterial expression, purification, and analysis. Site‐directed mutagenesis was used to alter the amino acids known to be post‐translationally modified to amino acids mimicking either the modified or unmodified state. Purified mutants and wild type TFB2M were analyzed in a mtDNA binding assay to determine the effects of PTMs on TFB2M function. Initial data suggest that TFB2M relies on modified or unmodified states of key PTM sites to regulate its ability to bind to mtDNA. Characterization of these sites is critical for determining TFB2M's role in mtDNA transcriptional regulation. Future work involves additional screening of TFB2M mutants, optimization of the mtDNA binding assay for analysis of other nucleoid proteins, and in vitro transcription assays to assess mutant protein functionality on mtDNA transcription.Support or Funding InformationThis research 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.