Browsing by Author "Tourigny, Jason P."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Architectural Mediator subunits are differentially essential for global transcription in Saccharomyces cerevisiae
    (Oxford University Press, 2021) Tourigny, Jason P.; Schumacher, Kenny; Saleh, Moustafa M.; Devys, Didier; Zentner, Gabriel E.; Biology, School of Science
    Mediator is a modular coactivator complex involved in the transcription of the majority of RNA polymerase II-regulated genes. However, the degrees to which individual core subunits of Mediator contribute to its activity have been unclear. Here, we investigate the contribution of two essential architectural subunits of Mediator to transcription in Saccharomyces cerevisiae. We show that acute depletion of the main complex scaffold Med14 or the head module nucleator Med17 is lethal and results in global transcriptional downregulation, though Med17 removal has a markedly greater negative effect. Consistent with this, Med17 depletion impairs preinitiation complex (PIC) assembly to a greater extent than Med14 removal. Co-depletion of Med14 and Med17 reduced transcription and TFIIB promoter occupancy similarly to Med17 ablation alone, indicating that the contributions of Med14 and Med17 to Mediator function are not additive. We propose that, while the structural integrity of complete Mediator and the head module are both important for PIC assembly and transcription, the head module plays a greater role in this process and is thus the key functional module of Mediator in this regard.
  • Thumbnail Image
    Item
    Renal L-2-hydroxyglutarate dehydrogenase activity promotes hypoxia tolerance and mitochondrial metabolism in Drosophila melanogaster
    (Elsevier, 2024) Mahmoudzadeh, Nader H.; Heidarian, Yasaman; Tourigny, Jason P.; Fitt, Alexander J.; Beebe, Katherine; Li, Hongde; Luhur, Arthur; Buddika, Kasun; Mungcal, Liam; Kundu, Anirban; Policastro, Robert A.; Brinkley, Garrett J.; Zentner, Gabriel E.; Nemkov, Travis; Pepin, Robert; Chawla, Geetanjali; Sudarshan, Sunil; Rodan, Aylin R.; D’Alessandro, Angelo; Tennessen, Jason M.; Medicine, School of Medicine
    Objectives: The mitochondrial enzyme L-2-hydroxyglutarate dehydrogenase (L2HGDH) regulates the abundance of L-2-hydroxyglutarate (L-2HG), a potent signaling metabolite capable of influencing chromatin architecture, mitochondrial metabolism, and cell fate decisions. Loss of L2hgdh activity in humans induces ectopic L-2HG accumulation, resulting in neurodevelopmental defects, altered immune cell function, and enhanced growth of clear cell renal cell carcinomas. To better understand the molecular mechanisms that underlie these disease pathologies, we used the fruit fly Drosophila melanogaster to investigate the endogenous functions of L2hgdh. Methods: L2hgdh mutant adult male flies were analyzed under normoxic and hypoxic conditions using a combination of semi-targeted metabolomics and RNA-seq. These multi-omic analyses were complemented by tissue-specific genetic studies that examined the effects of L2hgdh mutations on the Drosophila renal system (Malpighian tubules; MTs). Results: Our studies revealed that while L2hgdh is not essential for growth or viability under standard culture conditions, L2hgdh mutants are hypersensitive to hypoxia and expire during the reoxygenation phase with severe disruptions of mitochondrial metabolism. Moreover, we find that the fly renal system is a key site of L2hgdh activity, as L2hgdh mutants that express a rescuing transgene within the MTs survive hypoxia treatment and exhibit normal levels of mitochondrial metabolites. We also demonstrate that even under normoxic conditions, L2hgdh mutant MTs experience significant metabolic stress and are sensitized to aberrant growth upon Egfr activation. Conclusions: These findings present a model in which renal L2hgdh activity limits systemic L-2HG accumulation, thus indirectly regulating the balance between glycolytic and mitochondrial metabolism, enabling successful recovery from hypoxia exposure, and ensuring renal tissue integrity.