title: Regulation of the promoter for human immunoglobulin gamma3 germ-line transcription and its interaction with the 3'alpha enhancer.
abstract: The mechanism underlying the differential regulation of switching to human IgG subclasses is still largely unknown. We demonstrate that the region upstream of the initiation sites for gamma3 germ-line (GL) transcripts contains a functional promoter which is synergistically induced by IL-4, antibody to CD40 and phorbol dibutyrate in transient transfection assays in the human DG75 cell line. Linker-scanning mutations identified multiple elements in the 3' half of the evolutionarily conserved sequence that are required for inducibility. Electrophoretic mobility shift assays showed that Stat6 and NF-kappaB p50 / p65 are induced after stimulation, and bind to specific sequence motifs within the promoter. Overexpression of Stat6, NF-kappaB p50 / p65 and C / EBPgamma synergistically induced the GL gamma3 promoter. Insertion of DNA segments from the human 3' IgH regions, which may function as a locus control region for switch recombination, greatly activated the promoter in an orientation-independent manner. Duplication of the enhancer fragments resulted in a further increase of promoter activity. The greater enhancement of the HS1,2 fragment from the 3' alpha1 rather than the alpha2 locus may suggest a mechanistic explanation for the differential expression of various isotypes.
authors.affiliation: Division of Clinical Immunology, IMPI, Karolinska Institutet at Huddinge Hospital, Huddinge, Sweden.
authors.forename: Q
authors.initials: Q
authors.lastname: Pan
authors.forename: C
authors.initials: C
authors.lastname: Petit-Frére
authors.forename: J
authors.initials: J
authors.lastname: Stavnezer
authors.forename: L
authors.initials: L
authors.lastname: Hammarström
mesh_terms: D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins; D019013:CD40 Antigens / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004357:Drug Synergism; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D005803:Genes, Immunoglobulin / Q000235:genetics; D006801:Humans; D017578:Immunoglobulin Class Switching / Q000235:genetics; D007074:Immunoglobulin G / Q000235:genetics*; D015847:Interleukin-4 / Q000494:pharmacology; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000235:genetics; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D050800:STAT6 Transcription Factor; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*; D015533:Transcriptional Activation / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D019013:CD40 Antigens; D004268:DNA-Binding Proteins; D007074:Immunoglobulin G; D016328:NF-kappa B; D009687:Nuclear Proteins; D012333:RNA, Messenger; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D015534:Trans-Activators; D015847:Interleukin-4; D015240:Phorbol 12,13-Dibutyrate; D004247:DNA