Transcriptional regulation of the human growth hormone receptor (hGHR) gene V2 promoter by transcriptional activators and repressor.
The V2 transcript is the major ubiquitously expressed human GH receptor (hGHR) mRNA in all tissues examined to date. In a previous investigation, we defined the V2 promoter as TATA-less and exhibiting many characteristics of a housekeeping gene promoter. We also demonstrated that its basal activity is determined by several different cis-regulatory regions within both the promoter and the V2 exon. In the present study, we used luciferase-reporter, site-directed mutagenesis, gel shift, chromatin immunoprecipitation, and quantitative RT-PCR assays to investigate the ability of certain transcription factors to regulate hGHR V2 transcription through these regions in mammalian cells, including human adipocytes. Ets1 was found to transactivate the V2 proximal promoter through specific Ets sites. Two CCAAT/enhancer-binding protein (C/EBP) family members [C/EBP-homologous protein (CHOP) and C/EBPbeta] enhanced V2 transcription via different pathways: indirectly, by association with a V2 exon region (CHOP), and directly, using a V2 proximal promoter noncanonical binding site (C/EBPbeta). The Notch signaling mediator, Hes1, potently suppressed V2 promoter activity through interaction with two Hes sites within the V2 exon. We propose that these transcriptional factors regulate hGHR V2 expression by acting as downstream nuclear effectors, linking specific signaling cascades (e.g. MAPK and Notch) triggered by different growth factor-, development-, and nutrition- as well as stress-related stimuli. Our data also suggest that these factors are likely to be important in the differentiation-induced increase in V2 mRNA expression in adipocytes, with Ets1 and CHOP functioning at the preadipocyte stage to prepare the cells for differentiation and increasing C/EBPs and decreasing Hes1 levels contributing during adipocyte maturation.
Wei
Yuhong
Y
McGill University Health Centre-Montreal Children's Hospital Research Institute, 4060 St. Catherine West, Room 415-1, Montreal, Quebec, Canada H3Z 2Z3.
Puzhko
Svetlana
S
Wabitsch
Martin
M
Goodyer
Cynthia Gates
CG
D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism / Q000502:physiology; D001665:Binding Sites; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000378:metabolism / Q000502:physiology; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics*; D008954:Models, Biological; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000502:physiology; D011485:Protein Binding; D050784:Proto-Oncogene Protein c-ets-1 / Q000378:metabolism / Q000502:physiology; D012097:Repressor Proteins / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators / Q000502:physiology*; D051742:Transcription Factor CHOP / Q000378:metabolism / Q000502:physiology; D000072056:Transcription Factor HES-1
D051792:Basic Helix-Loop-Helix Proteins; D018398:Homeodomain Proteins; D008565:Membrane Proteins; D050784:Proto-Oncogene Protein c-ets-1; D012097:Repressor Proteins; D015534:Trans-Activators; D051742:Transcription Factor CHOP; D000072056:Transcription Factor HES-1; C497249:DDIT3 protein, human; C494041:ETS1 protein, human; C405010:delta-hGHR; C078493:HES1 protein, human