Ciglitazone-induced p27 gene transcriptional activity is mediated through Sp1 and is negatively regulated by the MAPK signaling pathway

Fei Chen, Eugene Kim, Chia Chi Wang, Lawrence Harrison

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

We have previously demonstrated that the PPARγ ligand, ciglitazone, increases p27kip1 protein levels in HT-29 colon cancer cells through both inhibition of proteasome associated degradation and activation of transcriptional activity. [F. Chen, L.E. Harrison, Cell Signal. 17 (2005) 809] The purpose of this investigation was to further elucidate the mechanism of ciglitazone-induced activation of p27 gene transcription. We observed that the region - 774 / - 462 of the p27 promoter plays a key role in ciglitazone-induced gene transcriptional activity and this region contains two Sp1 binding sites. When the p27PF-luc reporter was co-transfected with Sp1 expression plasmids, ciglitazone-induced p27PF-luc activity significantly increased, while mithramycin A, a Sp1 inhibitor, was able to abrogate its effects. Ciglitazone exposure increased both Sp1 protein expression and Sp1-DNA binding, which was also associated with a decrease of Erk1/2 phosphorylation. A similar increase of Sp1-DNA binding was observed when phosphorylation of Erk1/2 was inhibited by pretreatment with the MAP kinase inhibitor, U0126. In addition, a significant increase of p27PF-luc reporter luciferase activity was noted after MAP kinase inhibition, which could be abolished with co-treatment with mithramycin A. Based on these data, we postulate that ciglitazone induces p27 gene transcription through increased Sp1 binding to its promoter region, which in turn is mediated through increased Sp1 protein levels and decreased inhibitory regulation by the MAP kinase pathway.

Original languageEnglish (US)
Pages (from-to)1572-1577
Number of pages6
JournalCellular Signalling
Volume17
Issue number12
DOIs
StatePublished - Dec 1 2005
Externally publishedYes

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Genes
Phosphotransferases
Transcriptional Activation
Phosphorylation
Cyclin-Dependent Kinase Inhibitor p27
Peroxisome Proliferator-Activated Receptors
DNA
Proteasome Endopeptidase Complex
Luciferases
Genetic Promoter Regions
Colonic Neoplasms
ciglitazone
Proteins
Neutrophils
Plasmids
Binding Sites
Ligands
mithramycin A
U 0126

All Science Journal Classification (ASJC) codes

  • Cell Biology

Cite this

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title = "Ciglitazone-induced p27 gene transcriptional activity is mediated through Sp1 and is negatively regulated by the MAPK signaling pathway",
abstract = "We have previously demonstrated that the PPARγ ligand, ciglitazone, increases p27kip1 protein levels in HT-29 colon cancer cells through both inhibition of proteasome associated degradation and activation of transcriptional activity. [F. Chen, L.E. Harrison, Cell Signal. 17 (2005) 809] The purpose of this investigation was to further elucidate the mechanism of ciglitazone-induced activation of p27 gene transcription. We observed that the region - 774 / - 462 of the p27 promoter plays a key role in ciglitazone-induced gene transcriptional activity and this region contains two Sp1 binding sites. When the p27PF-luc reporter was co-transfected with Sp1 expression plasmids, ciglitazone-induced p27PF-luc activity significantly increased, while mithramycin A, a Sp1 inhibitor, was able to abrogate its effects. Ciglitazone exposure increased both Sp1 protein expression and Sp1-DNA binding, which was also associated with a decrease of Erk1/2 phosphorylation. A similar increase of Sp1-DNA binding was observed when phosphorylation of Erk1/2 was inhibited by pretreatment with the MAP kinase inhibitor, U0126. In addition, a significant increase of p27PF-luc reporter luciferase activity was noted after MAP kinase inhibition, which could be abolished with co-treatment with mithramycin A. Based on these data, we postulate that ciglitazone induces p27 gene transcription through increased Sp1 binding to its promoter region, which in turn is mediated through increased Sp1 protein levels and decreased inhibitory regulation by the MAP kinase pathway.",
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Ciglitazone-induced p27 gene transcriptional activity is mediated through Sp1 and is negatively regulated by the MAPK signaling pathway. / Chen, Fei; Kim, Eugene; Wang, Chia Chi; Harrison, Lawrence.

In: Cellular Signalling, Vol. 17, No. 12, 01.12.2005, p. 1572-1577.

Research output: Contribution to journalArticle

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