title: Regulation of expression of the human lymphocyte activation gene-3 (LAG-3) molecule, a ligand for MHC class II.
abstract: The lymphocyte activation gene-3 (LAG-3), a major histocompatibility complex (MHC) class II ligand evolutionarily related to CD4, is expressed exclusively in activated T and NK lymphocytes and seems to play a role in regulating the evolving immune response. We first determined that surface LAG-3 expression on activated human T cells is upregulated by certain cytokines (IL-2, IL-7, IL-12) and not by others (IL-4, IL-6, IL-10, TNF-alpha, TNF-beta, IFN-gamma). Surface LAG-3 expression correlated with intracellular IFN-gamma production in both CD4+ and CD8+ T-cell subsets. We then analyzed the 5' transcription control sequences of LAG-3. A DNase I hypersensitive site induced in T cells following cellular activation was found in the region including the transcriptional start site, showing that DNA accessibility is a mechanism which restricts LAG-3 expression to activated T cells. Transcription is initiated at three sites. A GC box, 80 base pairs (bp) upstream of the major transcription start site, forms a minimal promoter which is regulated by two upstream regions containing positive and negative regulatory elements with multiple protein binding sites as shown by footprinting analysis. In particular, a GATA/c-Ets motive was identified in a short segment homologous to the mouse CD4 distal enhancer, suggesting that LAG-3, which is embedded in the CD4 locus, may be controlled by some CD4 regulatory elements. Finally, a 100 bp region downstream of the transcription start site was shown to be involved in the cell-specific control of LAG-3 expression. Understanding this highly regulated expression may help to determine the intriguing role of this activation-induced MHC class II ligand.
authors.affiliation: Laboratoire d'Immunologie Cellulaire, Institut Gustave Roussy 39, rue Camille Desmoulins, F-94805 Villejuif Cedex, France.
authors.forename: D
authors.initials: D
authors.lastname: Bruniquel
authors.forename: N
authors.initials: N
authors.lastname: Borie
authors.forename: S
authors.initials: S
authors.lastname: Hannier
authors.forename: F
authors.initials: F
authors.lastname: Triebel
mesh_terms: D015703:Antigens, CD; D001483:Base Sequence; D015704:CD4 Antigens / Q000235:genetics; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D018983:DNA Footprinting; D004742:Enhancer Elements, Genetic; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis; D007378:Interleukins / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000276:immunology*; D008024:Ligands; D008213:Lymphocyte Activation / Q000235:genetics*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D014158:Transcription, Genetic; D015854:Up-Regulation; D000093322:Lymphocyte Activation Gene 3 Protein
chemical_list: D015703:Antigens, CD; D015704:CD4 Antigens; D000949:Histocompatibility Antigens Class II; D007378:Interleukins; D008024:Ligands; D008565:Membrane Proteins; D007371:Interferon-gamma; D000093322:Lymphocyte Activation Gene 3 Protein; C000720326:Lag3 protein, human