5-azaC treatment enhances expression of transforming growth factor-beta receptors through down-regulation of Sp3.
We have previously reported that Sp3 acts as a transcriptional repressor of transforming growth factor-beta receptors type I (RI) and type II (RII). We now present data suggesting that treatment of MCF-7L breast and GEO colon cancer cells with 5-aza cytidine (5-azaC) leads to down-regulation of Sp3 and the concomitant induction of RI and RII. Western blot and gel shift analyses on 5-azaC-treated MCF-7L and GEO nuclear extracts indicated reduced Sp3 protein levels and decreased binding of Sp3 protein to radiolabeled consensus Sp1 oligonucleotide. Southwestern analysis detected decreased binding of Sp3 to RI and RII promoters in 5-azaC-treated MCF-7L and GEO cells, suggesting a correlation between decreased Sp3 binding and enhanced RI and RII expression in these cells. Reverse transcription-polymerase chain reaction and nuclear run-on data from 5-azaC-treated MCF-7L and GEO cells indicated down-regulation of Sp3 mRNA as a result of decreased transcription of Sp3. We reported earlier that 5-azaC treatment induces RI and RII expression through increased Sp1 protein levels/activities in these cells. These studies demonstrate that the effect of 5-azaC involves a combination of effects on Sp1 and Sp3.
Ammanamanchi
S
S
Department of Surgery, The University of Texas Health Science Center, San Antonio, Texas 78229, USA.
Brattain
M G
MG
D030201:Activin Receptors, Type I; D001374:Azacitidine / Q000494:pharmacology*; D001943:Breast Neoplasms; D002467:Cell Nucleus / Q000378:metabolism; D003110:Colonic Neoplasms; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics*; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051705:Sp3 Transcription Factor; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D018125:Receptors, Transforming Growth Factor beta; D011994:Recombinant Proteins; C497121:SP3 protein, human; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D001374:Azacitidine