title: A CCAAT/enhancer-binding protein site at -87 is required for the activation of a novel murine melanocortin 2-receptor promoter at late stages during adipogenesis.
abstract: The peptide hormone ACTH stimulates lipolysis and suppresses leptin production in adipocytes via the G protein-coupled receptor, melanocortin 2 receptor (MC2-R). We have shown previously that peroxisome proliferator-activated receptor-gamma2 is the primary factor responsible for transactivation of the already identified murine MC2-R promoter in the differentiating 3T3-L1 adipocyte cell line. In this study we show that despite the activity of this promoter being transient during differentiation, MC2-R message remains elevated at later time points during adipogenesis. Analysis of the late transcripts reveals that they initiate from a transcriptional start site in the first intron of the murine MC2-R. The genomic sequence upstream of this start site acts as an adipocyte-specific promoter whose activation is delayed in differentiation, compared with the upstream promoter. A CCAAT/enhancer-binding protein binding site, 87 bp upstream of the transcriptional initiation site, is necessary for the activity of this promoter, and protein binding analyses reveal that this site is bound by CCAAT/enhancer-binding protein factors. Real-time PCR analysis of mRNA initiating from the two start sites shows that there is a switch in promoter usage from the 5' to the 3' promoter around d 5, indicating the complex regulation of the murine MC2-R during adipogenesis.
authors.affiliation: Molecular Endocrinology Centre, William Harvey Research Institute, Charterhouse Square, Bart's and The London, Queen Mary, University of London, London EC1M 6BQ, United Kingdom.
authors.forename: Luke A
authors.initials: LA
authors.lastname: Noon
authors.forename: Adrian J L
authors.initials: AJ
authors.lastname: Clark
authors.forename: Peter J
authors.initials: PJ
authors.lastname: O'Shaughnessy
authors.forename: Peter J
authors.initials: PJ
authors.lastname: King
mesh_terms: D041721:3T3-L1 Cells / Q000166:cytology; D050156:Adipogenesis / Q000235:genetics*; D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D018387:Codon, Initiator / Q000032:analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D005091:Exons; D007438:Introns / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000032:analysis; D044103:Receptor, Melanocortin, Type 2 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D050436:Regulatory Elements, Transcriptional / Q000502:physiology*; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D018387:Codon, Initiator; D004268:DNA-Binding Proteins; D020033:Protein Isoforms; D044103:Receptor, Melanocortin, Type 2