title: Transcriptional regulatory elements within the first intron of Bruton's tyrosine kinase.
abstract: Defects in the gene for Bruton's tyrosine kinase (Btk) result in the disorder X-linked agammaglobulinemia (XLA). Whereas XLA is characterized by a profound defect in B-cell development, Btk is expressed in both the B lymphocyte and myeloid cell lineages. We evaluated a patient with XLA who had reduced amounts of Btk transcript but no abnormalities in his coding sequence. A single base-pair substitution in the first intron of Btk was identified in this patient, suggesting that this region may contain regulatory elements. Using reporter constructs we identified two transcriptional control elements in the first 500 bp of intron 1. A strong positive regulator, active in both pre-B cells and B cells, was identified within the first 43 bp of the intron. Gel-shift assays identified two Sp1 binding sites within this element. The patient's mutation results in an altered binding specificity of the proximal Sp1 binding site. A negative regulator, active in pre-B cells only, was located between base pairs 281 and 491 of the intron. These findings indicate that regulation of Btk transcription is complex and may involve several transcriptional regulatory factors at the different stages of B-cell differentiation.
authors.affiliation: Department of Immunology, St Jude Children's Research Hospital, Memphis, Tennessee 38101, USA.
authors.forename: J
authors.initials: J
authors.lastname: Rohrer
authors.forename: M E
authors.initials: ME
authors.lastname: Conley
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000361:Agammaglobulinemia / Q000235:genetics; D016175:B-Lymphocyte Subsets / Q000201:enzymology; D002478:Cells, Cultured; D004790:Enzyme Induction; D005260:Female; D017930:Genes, Reporter; D006801:Humans; D007438:Introns / Q000235:genetics*; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D010375:Pedigree; D018807:Polymorphism, Single-Stranded Conformational; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014960:X Chromosome / Q000235:genetics
chemical_list: D011993:Recombinant Fusion Proteins; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human