title: Transcriptional regulation of human CD5: important role of Ets transcription factors in CD5 expression in T cells.
abstract: CD5 is a surface receptor constitutively expressed on thymocytes and mature T and B-1a cells. CD5 expression is tightly regulated during T and B cell development and activation processes. In this study we shown that the constitutive expression of CD5 on human T cells correlates with the presence of a DNase I-hypersensitive (DH) site at the 5'-flanking region of CD5. Human CD5 is a TATA-less gene for which 5'-RACE analysis shows multiple transcriptional start sites, the most frequent of which locates within an initiator sequence. Luciferase reporter assays indicate that a 282-bp region upstream of the initiation ATG displays full promoter activity in human T cells. Two conserved Ets-binding sites (at positions -239 and -185) were identified as functionally relevant to CD5 expression by site-directed mutagenesis, EMSAs, and cotransfection experiments. A possible contribution of Sp1 (-115 and -95), c-Myb (-177), and AP-1-like (-151) motifs was also detected. Further DH site analyses revealed an inducible DH site 10 kb upstream of the human CD5 gene in both T and B CD5(+) cells. Interestingly, a 140-bp sequence showing high homology with a murine inducible enhancer is found within that site. The data presented indicate that the 5'-flanking region of human CD5 is transcriptionally active in T cells, and that Ets transcription factors in conjunction with other regulatory elements are responsible for constitutive and tissue-specific CD5 expression.
authors.affiliation: Servei d'Immunologia, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Hospital Clínic i Provincial de Barcelona, Villaroel 170, Barcelona 08036, Spain.
authors.forename: Mònica
authors.initials: M
authors.lastname: Arman
authors.forename: Javier
authors.initials: J
authors.lastname: Calvo
authors.forename: Maria E
authors.initials: ME
authors.lastname: Trojanowska
authors.forename: Peter N
authors.initials: PN
authors.lastname: Cockerill
authors.forename: Mónica
authors.initials: M
authors.lastname: Santana
authors.forename: Manuel
authors.initials: M
authors.lastname: López-Cabrera
authors.forename: Jordi
authors.initials: J
authors.lastname: Vives
authors.forename: Francisco
authors.initials: F
authors.lastname: Lozano
mesh_terms: D024506:5' Flanking Region / Q000235:genetics*; D001402:B-Lymphocytes / Q000378:metabolism; D001665:Binding Sites; D018956:CD5 Antigens / Q000096:biosynthesis / Q000235:genetics*; D045744:Cell Line, Tumor; D003850:Deoxyribonuclease I / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D050783:Proto-Oncogene Proteins c-ets; D013601:T-Lymphocytes / Q000378:metabolism*; D014157:Transcription Factors / Q000502:physiology*; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
chemical_list: D018956:CD5 Antigens; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D014157:Transcription Factors; D003850:Deoxyribonuclease I