title: The DLK gene is a transcriptional target of PPARγ.
abstract: DLK (dual leucine zipper-bearing kinase) is a key regulator of development, cell differentiation and apoptosis. Interestingly, recent studies have shown that DLK expression is up-regulated in 3T3-L1 cells induced to differentiate into adipocytes and that DLK knockdown impairs the expression of PPARγ (peroxisome-proliferator-activated receptor γ), a master regulator of adipogenesis. Because the PPARγ agonist rosiglitazone was found to increase DLK expression in 3T3-L1 cells, we hypothesized that PPARγ is required for the transcriptional activation of the DLK gene. To test this hypothesis, we first examined the effects of pharmacological inhibition or shRNA (small-hairpin RNA)-mediated depletion of PPARγ on DLK accumulation in 3T3-L1 cells undergoing differentiation. In addition to blocking adipocyte conversion of 3T3-L1 cells, inhibition of PPARγ suppressed DLK expression at both the mRNA and protein levels. Moreover, supporting a role for PPARγ in DLK regulation, two potential PPARγ-binding sites identified by bioinformatic tools at positions -611 and -767 upstream of the DLK gene transcriptional start site were shown by electrophoretic mobility-shift assay and chromatin immunoprecipitation to bind PPARγ and its essential heterodimer partner retinoid X receptor as differentiation proceeds. Collectively, these results show that DLK is a novel transcriptional target of PPARγ with functional PPARγ-binding sites in its promoter.
authors.affiliation: Département de Biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, QC, Canada, J1K 2R1.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Couture
authors.forename: Richard
authors.initials: R
authors.lastname: Blouin
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D050156:Adipogenesis / Q000502:physiology*; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002135:Calcium-Binding Proteins; D002454:Cell Differentiation / Q000187:drug effects; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D016086:Lentivirus / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D047495:PPAR gamma / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000494:pharmacology; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D002135:Calcium-Binding Proteins; C512941:DLK1 protein, human; D007004:Hypoglycemic Agents; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D047495:PPAR gamma; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D045162:Thiazolidinediones; D000077154:Rosiglitazone