title: T cell activation regulates CD6 alternative splicing by transcription dynamics and SRSF1.
abstract: The T cell-surface glycoprotein CD6 is a modulator of cellular responses and has been implicated in several autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, and psoriasis. During Ag presentation, CD6 is targeted to the immunological synapse in a ligand binding-dependent manner, in which CD6 domain 3 directly contacts CD166, expressed on the APC. T cell activation results in the induction of CD6Δd3, an alternatively spliced isoform that lacks the ligand-binding domain and thus no longer localizes at the immunological synapse. In this study, we investigated the molecular mechanisms regulating the expression of CD6Δd3 upon human primary T cell activation. Using chromatin immunoprecipitation, we observed an increase in RNA polymerase II occupancy along the CD6 gene and augmented CD6 transcription. We showed that activation leads to transcription-related chromatin modifications, revealed by higher CD6 acetylation levels. Modulation of chromatin conformation using a histone deacetylase inhibitor that increases transcription rate causes an increase of exon 5 skipping. We further showed that the splicing factor SRSF1 binds to a regulatory element in CD6 intron 4, activating exon 5 splicing and promoting exon 5 inclusion. Concomitant with T cell activation-induced exon 5 skipping, we observed a downregulation of SRSF1. Using RNA immunoprecipitation, we showed that in activated T cells, SRSF1 recruitment to the CD6 transcript is impaired by increased chromatin acetylation levels. We propose that upon T cell activation, SRSF1 becomes limiting, and its function in CD6 exon 5 splicing is countered by an increase in CD6 transcription, dependent on chromatin acetylation.
authors.affiliation: Grupo Regulação Genética, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal;
authors.forename: Vânia G
authors.initials: VG
authors.lastname: da Glória
authors.affiliation: Grupo Activação Celular e Expressão Genética, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal; Instituto de Investigação em Ciências da Vida e da Saude, Escola de Ciências da Saude, Universidade do Minho, Braga 4710-057, Portugal; ICVS/3B's Laboratório Associado, Braga/Guimarães 4806-909, Portugal;
authors.forename: Mafalda
authors.initials: M
authors.lastname: Martins de Araújo
authors.affiliation: Grupo Activação Celular e Expressão Genética, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal;
authors.forename: Ana
authors.initials: A
authors.lastname: Mafalda Santos
authors.affiliation: Grupo Regulação Genética, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal;
authors.forename: Rafaela
authors.initials: R
authors.lastname: Leal
authors.affiliation: Instituto de Medicina Molecular, Faculdade de Medicina, Universidade Lisboa, Lisboa 1649-028, Portugal; and.
authors.forename: Sérgio F
authors.initials: SF
authors.lastname: de Almeida
authors.affiliation: Grupo Activação Celular e Expressão Genética, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal; Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto 4050-313, Portugal alexandra.moreira@ibmc.up.pt acarmo@ibmc.up.pt.
authors.forename: Alexandre M
authors.initials: AM
authors.lastname: Carmo
authors.affiliation: Grupo Regulação Genética, Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto 4150-180, Portugal; alexandra.moreira@ibmc.up.pt acarmo@ibmc.up.pt.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Moreira
mesh_terms: D000107:Acetylation; D017398:Alternative Splicing / Q000502:physiology*; D000938:Antigen-Presenting Cells / Q000166:cytology / Q000276:immunology; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000235:genetics / Q000276:immunology*; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics / Q000276:immunology; D002843:Chromatin / Q000235:genetics / Q000276:immunology; D005260:Female; D005326:Fetal Proteins / Q000235:genetics / Q000276:immunology; D006801:Humans; D007438:Introns / Q000276:immunology; D008213:Lymphocyte Activation / Q000502:physiology*; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics / Q000276:immunology*; D012319:RNA Polymerase II / Q000235:genetics / Q000276:immunology; D016601:RNA-Binding Proteins / Q000235:genetics / Q000276:immunology*; D000068103:Serine-Arginine Splicing Factors; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D014158:Transcription, Genetic / Q000235:genetics / Q000276:immunology*; D020410:Activated-Leukocyte Cell Adhesion Molecule
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D015816:Cell Adhesion Molecules, Neuronal; D002843:Chromatin; D005326:Fetal Proteins; D009687:Nuclear Proteins; D012319:RNA Polymerase II; D016601:RNA-Binding Proteins; D000068103:Serine-Arginine Splicing Factors; C105613:ALCAM protein, human; D020410:Activated-Leukocyte Cell Adhesion Molecule; C062279:CD6 antigen