title: Mediator subunit Gal11p/MED15 is required for fatty acid-dependent gene activation by yeast transcription factor Oaf1p.
abstract: The yeast zinc cluster transcription factor Oaf1p activates transcription of target genes in response to direct binding of fatty acids in a manner analogous to the vertebrate nuclear receptor peroxisome proliferator-activated receptoralpha (PPARalpha). PPARs and other metazoan nuclear receptors productively engage several distinct LXXLL motif-containing co-activators, including p160 family members and the TRAP220/MED1 subunit of the Mediator co-activator, to promote ligand-dependent gene activation. Yeast, however, does not appear to harbor LXXLL motif co-activators, and the mechanism of fatty acid-dependent gene activation by the yeast PPARalpha analog Oaf1p is unknown. Here we show that the yeast Mediator subunit Gal11p/MED15 and its activator-targeted KIX domain plays a critical role in fatty acid-dependent transcriptional regulation of fatty acid beta-oxidation and peroxisomal genes by Oaf1p and for the ability of yeast to utilize fatty acids as a sole carbon source. Moreover, structural studies by NMR spectroscopy reveal that the Oaf1p activation domain interacts with the Gal11p/MED15 KIX domain in a manner similar to the yeast zinc cluster family member and xenobiotic receptor Pdr1p, revealing that the Gal11p/MED15 KIX domain is a key target of several ligand-dependent transcription factors in yeast. Together with previous work showing that the Caenorhabditis elegans Gal11p/MED15 homolog MDT-15 plays a critical role in regulation of fatty acid metabolism by the nematode PPAR-like nuclear receptor NHR-49, the findings presented here provide evidence for an ancient and essential role of a Mediator co-activator subunit in regulation of fatty acid metabolism by nuclear receptor-like transcription factors in eukaryotes.
authors.affiliation: Massachusetts General Hospital Cancer Center and the Department of Cell Biology, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: Jitendra K
authors.initials: JK
authors.lastname: Thakur
authors.forename: Haribabu
authors.initials: H
authors.lastname: Arthanari
authors.forename: Fajun
authors.initials: F
authors.lastname: Yang
authors.forename: Katherine H
authors.initials: KH
authors.lastname: Chau
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wagner
authors.forename: Anders M
authors.initials: AM
authors.lastname: Näär
mesh_terms: D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism / Q000502:physiology*; D056892:Mediator Complex; D019906:Nuclear Magnetic Resonance, Biomolecular; D017434:Protein Structure, Tertiary / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D005227:Fatty Acids; C058337:GAL11 protein, S cerevisiae; D056892:Mediator Complex; C120764:OAF1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors