TY - JOUR
T1 - Repression of transforming growth factor-β receptor type I promoter expression by Sp1 deficiency
AU - Periyasamy, Sumudra
AU - Ammanamanchi, Sudhakar
AU - Tillekeratne, Manoranjani P.M.
AU - Brattain, Michael G.
N1 - Funding Information:
This work was supported by National Institutes of Health grants CA 38173 and CA 72001. We thank R Goldstein for kindly providing the RI-Luc construct used in this study.
PY - 2000/9/21
Y1 - 2000/9/21
N2 - In this report, we describe the mechanism of TGF-β receptor type I (RI) repression in the GEO human colon carcinoma cells. Treatment of GEO cells with the DNA methyltransferase inhibitor, 5 azacytidine induced RI expression and restored TGF-β response. A stably transfected RI promoter-reporter construct (RI-Luc) expressed higher activity in the 5 aza C treated GEO cells, suggesting the activation of a transactivator for RI transcription. Gel shift analysis indicated enhanced binding of proteins from the 5 aza C treated nuclear extracts to radiolabeled Sp1 oligonucleotides specifically contained in the RI promoter. Protein stability studies after cyclohexamide treatment suggested an increase in the Sp1 protein stability from the 5 aza C treated GEO cells. Further, transfection of Sp1 cDNA into untreated GEO control cells increased RI promoter activity and thus induced RI expression. 5 aza C mediated Sp1 expression in Sp1 deficient GEO colon and MCF-7 breast cancer cells also enhanced the activity of several other Sp1 dependent promoters such as TGF-β receptor type II (RII), Cyclin A and p21/waf1/cip1. These results indicate that restoration of Sp1 in several different types of Sp1 deficient cells leads to enhanced activation of a wide range of Sp1 dependent promoters.
AB - In this report, we describe the mechanism of TGF-β receptor type I (RI) repression in the GEO human colon carcinoma cells. Treatment of GEO cells with the DNA methyltransferase inhibitor, 5 azacytidine induced RI expression and restored TGF-β response. A stably transfected RI promoter-reporter construct (RI-Luc) expressed higher activity in the 5 aza C treated GEO cells, suggesting the activation of a transactivator for RI transcription. Gel shift analysis indicated enhanced binding of proteins from the 5 aza C treated nuclear extracts to radiolabeled Sp1 oligonucleotides specifically contained in the RI promoter. Protein stability studies after cyclohexamide treatment suggested an increase in the Sp1 protein stability from the 5 aza C treated GEO cells. Further, transfection of Sp1 cDNA into untreated GEO control cells increased RI promoter activity and thus induced RI expression. 5 aza C mediated Sp1 expression in Sp1 deficient GEO colon and MCF-7 breast cancer cells also enhanced the activity of several other Sp1 dependent promoters such as TGF-β receptor type II (RII), Cyclin A and p21/waf1/cip1. These results indicate that restoration of Sp1 in several different types of Sp1 deficient cells leads to enhanced activation of a wide range of Sp1 dependent promoters.
KW - Azacytidine
KW - Transforming growth factor-β
KW - Transforming growth factor-β receptor type I (RI)
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U2 - 10.1038/sj.onc.1203822
DO - 10.1038/sj.onc.1203822
M3 - Article
C2 - 11030155
AN - SCOPUS:0034699344
SN - 0950-9232
VL - 19
SP - 4660
EP - 4667
JO - Oncogene
JF - Oncogene
IS - 40
ER -