Gain-of-Function Alleles in Caenorhabditis elegans Nuclear Hormone Receptor nhr-49 Are Functionally Distinct.

Autor: Lee K; Graduate Program in Medical Genetics, University of British Columbia, Vancouver, BC, Canada.; Centre for Molecular Medicine and Therapeutics and Child & Family Research Institute, University of British Columbia, Vancouver, BC, Canada., Goh GY; Centre for Molecular Medicine and Therapeutics and Child & Family Research Institute, University of British Columbia, Vancouver, BC, Canada.; Graduate Program in Cell and Developmental Biology, University of British Columbia, Vancouver, BC, Canada., Wong MA; Centre for Molecular Medicine and Therapeutics and Child & Family Research Institute, University of British Columbia, Vancouver, BC, Canada., Klassen TL; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada., Taubert S; Graduate Program in Medical Genetics, University of British Columbia, Vancouver, BC, Canada.; Centre for Molecular Medicine and Therapeutics and Child & Family Research Institute, University of British Columbia, Vancouver, BC, Canada.; Graduate Program in Cell and Developmental Biology, University of British Columbia, Vancouver, BC, Canada.; Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada.
Jazyk: angličtina
Zdroj: PloS one [PLoS One] 2016 Sep 12; Vol. 11 (9), pp. e0162708. Date of Electronic Publication: 2016 Sep 12 (Print Publication: 2016).
DOI: 10.1371/journal.pone.0162708
Abstrakt: Nuclear hormone receptors (NHRs) are transcription factors that regulate numerous physiological and developmental processes and represent important drug targets. NHR-49, an ortholog of Hepatocyte Nuclear Factor 4 (HNF4), has emerged as a key regulator of lipid metabolism and life span in the nematode worm Caenorhabditis elegans. However, many aspects of NHR-49 function remain poorly understood, including whether and how it regulates individual sets of target genes and whether its activity is modulated by a ligand. A recent study identified three gain-of-function (gof) missense mutations in nhr-49 (nhr-49(et7), nhr-49(et8), and nhr-49(et13), respectively). These substitutions all affect the ligand-binding domain (LBD), which is critical for ligand binding and protein interactions. Thus, these alleles provide an opportunity to test how three specific residues contribute to NHR-49 dependent gene regulation. We used computational and molecular methods to delineate how these mutations alter NHR-49 activity. We find that despite originating from a screen favoring the activation of specific NHR-49 targets, all three gof alleles cause broad upregulation of NHR-49 regulated genes. Interestingly, nhr-49(et7) and nhr-49(et8) exclusively affect nhr-49 dependent activation, whereas the nhr-49(et13) surprisingly affects both nhr-49 mediated activation and repression, implicating the affected residue as dually important. We also observed phenotypic non-equivalence of these alleles, as they unexpectedly caused a long, short, and normal life span, respectively. Mechanistically, the gof substitutions altered neither protein interactions with the repressive partner NHR-66 and the coactivator MDT-15 nor the subcellular localization or expression of NHR-49. However, in silico structural modeling revealed that NHR-49 likely interacts with small molecule ligands and that the missense mutations might alter ligand binding, providing a possible explanation for increased NHR-49 activity. In sum, our findings indicate that the three nhr-49 gof alleles are non-equivalent, and highlight the conserved V411 residue affected by et13 as critical for gene activation and repression alike.
Competing Interests: The authors have declared that no competing interests exist.
Databáze: MEDLINE
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