Txk, a member of nonreceptor tyrosine kinase of Tec family, acts as a Th1 cell-specific transcription factor and regulates IFN-gamma gene transcription.
Precise mechanisms responsible for Th1 cell activation and differentiation are not fully elucidated. We have recently reported that Txk, a member of Tec family nonreceptor tyrosine kinase, is expressed on Th1/Th0 cells, and Txk regulates specifically IFN-gamma gene expression. In this study, we found that Txk bound to IFN-gamma promoter region. Txk transfection increased transcriptional activity of IFN-gamma promoter plus luciferase constructs severalfold, including IFN-gamma promoter -538, -208, and -53. IFN-gamma promoter -39 was refractory to the Txk transfection. The actual site to which Txk bound was the element consisting of -53 and -39 bp from the transcription start site of human IFN-gamma gene, a site distinct from several previously characterized binding sites. We found that the entire -53/-39 region was necessary for the binding to and function of Txk, because mutant promoter oligoDNA that contained contiguous five base substitutions dispersed throughout the -53/-39 inhibited the binding, and the mutant promoters did not respond to the Txk transfection. Similar sequences of this element are found within the 5' flanking regions of several Th1 cell-associated protein genes. Thus, Txk is expressed on Th1/Th0 cells with the IFN-gamma production and acts as a Th1 cell-specific transcription factor.
Takeba
Yuko
Y
Department of Immunology and Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan.
Nagafuchi
Hiroko
H
Takeno
Mitsuhiro
M
Kashiwakura
Jun-ichi
J
Suzuki
Noboru
N
D001483:Base Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D024202:Electrophoretic Mobility Shift Assay; D017930:Genes, Reporter; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis / Q000235:genetics*; D019169:Jurkat Cells; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology*; D018417:Th1 Cells / Q000276:immunology*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection
D014157:Transcription Factors; D007371:Interferon-gamma; C089848:Tec protein-tyrosine kinase; D011505:Protein-Tyrosine Kinases