title: Murine txk: a protein tyrosine kinase gene regulated by T cell activation.
abstract: To identify genes involved in signal transduction pathways that regulate T cell activation and development, murine fetal thymocytes were screened for expression of protein tyrosine kinase family members by the polymerase chain reaction. Using this approach, a non-receptor protein tyrosine kinase, txk, was identified and cloned. Tsk is expressed in thymocytes as early as fetal day 13.5 and its expression at the mRNA level continues throughout development. Txk transcripts are present in thymocytes, peripheral T cells and mast cell lines, but are not detectable in B cell macrophage/monocyte cell lines or in non-hematopoietic fetal or adult tissues. In both thymocytes and T cells, txk transcripts are down-regulated after activation with PMA and ionomycin, concanavalin A or T cell receptor cross-linking. Sequence analysis indicates that txk contains SH2, SH3 and kinase catalytic domains and belongs to the tec family of cytoplasmic protein tyrosine kinases which includes tec, itk and btk. Its unique N-terminus contains a proline-rich region, but unlike the other tec family members, does not contain a pleckstrin homology domain. The restricted expression pattern of txk and its regulation by T cell activation make it an excellent candidate for involvement in signal transduction during thymocyte development.
authors.affiliation: Laboratory of Mammalian Genes and Development, NICHD, NIH, Bethesda, Maryland 20892, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Sommers
authors.forename: K
authors.initials: K
authors.lastname: Huang
authors.forename: E W
authors.initials: EW
authors.lastname: Shores
authors.forename: A
authors.initials: A
authors.lastname: Grinberg
authors.forename: D A
authors.initials: DA
authors.lastname: Charlick
authors.forename: C A
authors.initials: CA
authors.lastname: Kozak
authors.forename: P E
authors.initials: PE
authors.lastname: Love
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015704:CD4 Antigens / Q000187:drug effects / Q000502:physiology; D016827:CD8 Antigens / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003433:Crosses, Genetic; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D004622:Embryo, Mammalian / Q000166:cytology / Q000502:physiology; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D008213:Lymphocyte Activation; D008407:Mast Cells / Q000201:enzymology / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D010703:Phorbol Esters / Q000494:pharmacology; D016133:Polymerase Chain Reaction / Q000379:methods; D011505:Protein-Tyrosine Kinases / Q000097:blood / Q000235:genetics*; D012313:RNA / Q000737:chemistry / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D013950:Thymus Gland / Q000196:embryology / Q000201:enzymology / Q000502:physiology
chemical_list: D015704:CD4 Antigens; D016827:CD8 Antigens; D017931:DNA Primers; D018076:DNA, Complementary; D010703:Phorbol Esters; D012333:RNA, Messenger; D015759:Ionomycin; D012313:RNA; D011505:Protein-Tyrosine Kinases