Repression of transforming growth factor-beta receptor type I promoter expression by Sp1 deficiency

Oncogene. 2000 Sep 21;19(40):4660-7. doi: 10.1038/sj.onc.1203822.

Abstract

In this report, we describe the mechanism of TGF-beta 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-beta 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-beta 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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Activin Receptors, Type I*
  • Adenocarcinoma / genetics
  • Adenocarcinoma / metabolism
  • Adenocarcinoma / pathology
  • Antimetabolites, Antineoplastic / pharmacology
  • Azacitidine / pharmacology
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology
  • Cyclin A / biosynthesis
  • Cyclin A / genetics
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins / biosynthesis
  • Cyclins / genetics
  • DNA (Cytosine-5-)-Methyltransferases / antagonists & inhibitors
  • DNA Methylation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Female
  • Gene Expression Regulation, Neoplastic* / drug effects
  • Humans
  • Neoplasm Proteins / biosynthesis
  • Neoplasm Proteins / deficiency
  • Neoplasm Proteins / genetics*
  • Neoplasm Proteins / physiology*
  • Promoter Regions, Genetic / genetics*
  • Protein-Serine-Threonine Kinases / biosynthesis
  • Protein-Serine-Threonine Kinases / genetics*
  • Receptor, Transforming Growth Factor-beta Type I
  • Receptor, Transforming Growth Factor-beta Type II
  • Receptors, Transforming Growth Factor beta / biosynthesis
  • Receptors, Transforming Growth Factor beta / genetics*
  • Recombinant Fusion Proteins / physiology
  • Sp1 Transcription Factor / deficiency*
  • Sp1 Transcription Factor / physiology
  • Transcriptional Activation
  • Transfection
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / metabolism

Substances

  • Antimetabolites, Antineoplastic
  • CDKN1A protein, human
  • Cyclin A
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • Enzyme Inhibitors
  • Neoplasm Proteins
  • Receptors, Transforming Growth Factor beta
  • Recombinant Fusion Proteins
  • Sp1 Transcription Factor
  • DNA (Cytosine-5-)-Methyltransferases
  • Protein-Serine-Threonine Kinases
  • Activin Receptors, Type I
  • Receptor, Transforming Growth Factor-beta Type I
  • Receptor, Transforming Growth Factor-beta Type II
  • Azacitidine