Project description:Through a genetic screen in Drosophila melanogaster, CG1603 was identified as one of the transcription factors that coordinate mitochondrial biogenesis. To investigate the role of CG1603 in regulating nuclear-encoded mitochondrial gene expression, we collected second-instar larvae from wild type and CG1603PBac mutants (a mutant allele that disrupts the translation of the full-length CG1603 protein). We purified mRNA from the samples in triplicate and compared the mRNA transcriptome profiles (RNA-seq). We found that, between wild-type and CG1603PBac larvae, more than 80% of nuclear-encoded mitochondrial genes were differentially expressed. Nearly half of the nuclear-encoded mitochondrial genes were reduced by more than twofold in CG1603PBac mutants, including many structural subunit genes of all five ETC complexes. Gene Ontology (GO) enrichment analysis of the significantly downregulated genes also revealed that the most significantly enriched biological processes were related to mitochondria, including “mitochondrial translation,” “mitochondrial gene expression,” “electron transport chain,” “aerobic respiration,” and “ATP metabolic process.” These results suggest that CG1603 is essential for nuclear mitochondrial gene expression.
Project description:Mitochondrial biogenesis and function are controlled by anterograde regulatory pathways involving more than one thousand proteins encoded by nuclear genome. Transcriptional networks controlling the nuclear-encoded mitochondrial genes remain elucidated. Here we show that histone demethylase LSD1 knockout from adult mouse liver (LSD1-LKO) reduces one-third of all nuclear-encoded mitochondrial genes and decreases mitochondrial biogenesis and function. LSD1-modulated histone methylation epigenetically regulates nuclear-encoded mitochondrial genes. Furthermore, LSD1 targets methylation of nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1), the rate-limiting enzyme for nuclear NAD+ synthesis. Hepatic LSD1 knockout reduces NAD+-dependent Sirt1 and Sirt7 deacetylase activity, leading to hyperacetylation and hypofunctioning of GABP and PGC-1, the major transcriptional factor/cofactor for nuclear-encoded mitochondrial genes. Despite the reduced mitochondrial function, LSD1-LKO mice are protected from diet-induced hepatic steatosis and glucose intolerance, partially due to induction of hepatokine FGF21. Thus, LSD1 orchestrates a core regulatory network involving epigenetic modifications and NAD+ synthesis to control mitochondrial function and hepatokine production.
Project description:Mitochondrial biogenesis and function are controlled by anterograde regulatory pathways involving more than one thousand nuclear-encoded proteins. Transcriptional networks controlling the nuclear-encoded mitochondrial genes remain fully elucidated. Here we show that histone demethylase LSD1 knockout from adult mouse liver (LSD1-LKO) reduces one-third of all nuclear-encoded mitochondrial genes and decreases mitochondrial biogenesis and function. ChIP-seq analysis shows that LSD1 and LSD1-targeted H3K4me2 modulate the expression of mitochondrial genes in liver.
Project description:Nurr1 (Nr4a2, nuclear receptor subfamily 4 group A member 2) is needed for the development of ventral midbrain dopaminergic neurons, and has been associated with Parkinson's disease. We used mice where the Nurr1 gene is ablated by tamoxifen treatment selectively in dopaminergic neurons. As a control, we used tamoxifen-treated mice where Nurr1 is not ablated. By laser microdissection of neurons selected by their TH1 (Th1l, TH1-like homolog) gene expression, we selected dopaminergic neurons for RNA extraction and high-throughput mRNA sequencing, in order to identify genes regulated by Nurr1. We found the main functional category of Nurr1-regulated genes are the nuclear-encoded mitochondrial genes. Dopaminergic neurons with or without Nurr1 knocked out. TH-positive neurons were laser capture microdissected from cryostat coronal sections of the midbrain.
Project description:Current evidence suggests that nuclear-encoded mitochondrial proteins can be locally translated at the mitochondrial surface and co-translationally or post-translationally imported into mitochondria. mRNA localization on the mitochondrial membrane, a prerequisite for localized translation, remains uncharacterized in higher eukaryotic organisms. We employed fractionation-sequencing to profile mitochondria-associated mRNAs in zebrafish larvae. Our transcriptome-wide analysis reveals the localization of mRNAs of only 12% of the nuclear-encoded mitochondrial proteins to the mitochondrial surface, which suggests that post-translational import is the dominant mode of protein import to mitochondria. Additionally, the mRNAs which were localized to the mitochondrial membrane consisted mostly of those encoding proteins involved in mitochondrial dynamics, suggesting their site-specific translation. Finally, we show that the loss of function of the MIA pathway responsible for the post-translational import of a subclass of mitochondrial proteins, triggers mitochondrial localization of mRNAs encoding proteins that are imported to mitochondria via other pathways. Thus, our study suggests that mRNA targeting and localized translation could be relevant in higher eukaryotes to combat stress conditions affecting mitochondrial biogenesis in general.
Project description:Nurr1 (Nr4a2, nuclear receptor subfamily 4 group A member 2) is needed for the development of ventral midbrain dopaminergic neurons, and has been associated with Parkinson's disease. We used mice where the Nurr1 gene is ablated by tamoxifen treatment selectively in dopaminergic neurons. As a control, we used tamoxifen-treated mice where Nurr1 is not ablated. By laser microdissection of neurons selected by their TH1 (Th1l, TH1-like homolog) gene expression, we selected dopaminergic neurons for RNA extraction and high-throughput mRNA sequencing, in order to identify genes regulated by Nurr1. We found the main functional category of Nurr1-regulated genes are the nuclear-encoded mitochondrial genes.
Project description:Protein homeostasis in eukaryotic organelles and their progenitor prokaryotes is regulated by a series of ATP-dependent proteases including the caseinolytic protease complex (ClpXP). In chloroplasts, ClpXP has essential roles in organelle biogenesis and maintenance , but the significance of the plant mitochondrial ClpXP remains unknown and factors that aid coordination of nuclear and mitochondrial encoded subunits for complex assembly in mitochondria await discovery. In this study, we generated knock-out lines of the single copy mitochondrial Clp protease subunit, CLPP2, in Arabidopsis thaliana. They have higher abundance of transcripts from mitochondrial genes encoding OXPHOS protein complexes, while transcripts for nuclear genes encoding other subunits of the same complexes showed no change in transcript abundance. In contrast, the protein abundance of specific nuclear-encoded subunits in OXPHOS complexes I and V increased in knockouts, without accumulation of mitochondrial-encoded counterparts in the same complex. Protein complexes mainly or wholly encoded in the nucleus were unaffected. Analysis of protein import, assembly and function of Complex I revealed that while function was retained, protein homeostasis was disrupted through slower assembly, leading to accumulation of soluble subcomplexes of nuclear-encoded subunits after import. It is proposed that CLPP contributes to the mitochondrial protein degradation network through supporting coordination and assembly of protein complexes encoded across mitochondrial and nuclear genomes.