Transcriptional regulation of tristetraprolin by transforming growth factor-beta in human T cells.
Transforming growth factor-beta (TGF-beta) is a pleiotropic cytokine that plays a critical role in modulating immune response and inflammation. We employed the Affymetrix cDNA microarray system to detect genes whose expression is regulated by TGF-beta1 in a human T cell line HuT78. Tristetraprolin (TTP), a protein involved in the degradation of tumor necrosis factor-alpha (TNF-alpha) mRNA, was found to be up-regulated by TGF-beta. This up-regulation was confirmed by reverse transcriptase-PCR analysis that revealed a rapid and transient induction of TTP mRNA by TGF-beta 1 in HuT78 cells, primary human T cells, and THP-1 macrophage-monocyte cells. In addition, de novo protein synthesis was not required for this induction, suggesting that TTP is regulated by TGF-beta at the transcriptional level. To delineate the transcriptional regulation of the TTP gene, a 2.7-kb human TTP promoter region (-2682 to +56 bp relative to the transcription initiation site) was isolated. We found that this promoter was stimulated by TGF-beta 1 or a constitutively active TGF-beta type I receptor via TGF-beta-specific Smad proteins. Furthermore, a series of TTP promoter deletion constructs were used to localize the Smad-responsive region to the -583 to -263 bp portion of the promoter. In this region, the TTP promoter contained a stretch of putative Smad-binding elements that had a synergistic effect in mediating Smad activation of the promoter. These putative Smad-binding element-containing sequences were also able to bind Smad3 and Smad4 proteins purified in vitro. As TGF-beta- and TTP-deficient mice exhibit overlapping phenotypes manifested by multifocal inflammation and autoimmunity, our findings that TTP transcription is under the control of TGF-beta signaling would indicate a potential role of TTP in mediating the immune suppressive action of TGF-beta in vivo.
Ogawa
Kenji
K
Department of Medical and Molecular Genetics, Walther Oncology Center, Indiana University School of Medicine and the Walther Cancer Institute, Indianapolis, Indiana 46202, USA.
Chen
Feifei
F
Kim
Young-June
YJ
Chen
Yan
Y
D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis* / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D009841:Oligonucleotides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051900:Smad3 Protein; D051901:Smad4 Protein; D013601:T-Lymphocytes / Q000378:metabolism*; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D051816:Tristetraprolin; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D009841:Oligonucleotides; D012333:RNA, Messenger; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051900:Smad3 Protein; D051901:Smad4 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D051816:Tristetraprolin; D014409:Tumor Necrosis Factor-alpha; C497552:ZFP36 protein, human; D012313:RNA; D005982:Glutathione Transferase