Regulation of TG-interacting factor by transforming growth factor-beta.
TG-interacting factor (TGIF) is a transcriptional co-repressor that directly associates with Smad (Sma- and Mad-related protein) proteins and inhibits Smad-mediated transcriptional activation. By using Affymetrix (Santa Clara, CA, U.S.A.) oligonucleotide microarray analysis, we found that TGIF mRNA level was elevated by transforming-growth-factor-beta (TGF-beta) treatment in a human T-cell line, HuT78. Subsequent reverse-transcription PCR assays indicated that TGF-beta1 and activin were able to induce a rapid and transient increase in the level of TGIF in both HuT78 and HepG2 hepatoma cells. To analyse whether or not the regulation of TGIF mRNA occurs at the transcriptional level, a 2.4 kb human TGIF promoter was isolated. A primer extension assay was performed to localize the putative transcription initiation site of the promoter. When transiently expressed in HepG2 cells, this promoter was stimulated by TGF-beta1 and activin treatment in a time-dependent manner. A series of deletion mutants of the TGIF promoter were also generated to further characterize the TGF-beta responsive region of the promoter. In addition, expression of TGIF was able to cause a dose-dependent inhibition of TGF-beta and activin signalling. Taken together, these experiments indicated that TGIF is a novel transcriptional target of TGF-beta and activin signalling and is likely involved in a negative feedback loop to desensitize TGF-beta/activin action.
Chen
Feifei
F
Department of Medical Molecular Genetics, the Walther Oncology Center, Indiana University School of Medicine, the Walther Cancer Institute, Indianapolis, IN 46202, USA.
Ogawa
Kenji
K
Nagarajan
Raman P
RP
Zhang
Meiyu
M
Kuang
Chenzhong
C
Chen
Yan
Y
D001483:Base Sequence; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007668:Kidney; D007700:Kinetics; D008113:Liver Neoplasms; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051785:Smad Proteins; D013601:T-Lymphocytes; D015534:Trans-Activators / Q000378:metabolism; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D012097:Repressor Proteins; D051785:Smad Proteins; C097504:TGIF1 protein, human; D015534:Trans-Activators; D016212:Transforming Growth Factor beta