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"A direct intersection between p53 and transforming growth factor beta pathways targets chromatin modification and transcription repression of the alpha-fetoprotein gene."

Wilkinson DS, Ogden SK, Stratton SA, Piechan JL, Nguyen TT, Smulian GA, Barton MC

Published Jan. 1, 2005 in Mol Cell Biol volume 25 .

Pubmed ID: 15657445

We purified the oncoprotein SnoN and found that it functions as a corepressor of the tumor suppressor p53 in the regulation of the hepatic alpha-fetoprotein (AFP) tumor marker gene. p53 promotes SnoN and histone deacetylase interaction at an overlapping Smad binding, p53 regulatory element (SBE/p53RE) in AFP. Comparison of wild-type and p53-null mouse liver tissue by using chromatin immunoprecipitation (ChIP) reveals that the absence of p53 protein correlates with the disappearance of SnoN at the SBE/p53RE and loss of AFP developmental repression. Treatment of AFP-expressing hepatoma cells with transforming growth factor-beta1 (TGF-beta1) induced SnoN transcription and Smad2 activation, concomitant with AFP repression. ChIP assays show that TGF-beta1 stimulates p53, Smad4, P-Smad2 binding, and histone H3K9 deacetylation and methylation, at the SBE/p53RE. Depletion, by small interfering RNA, of SnoN and/or p53 in hepatoma cells disrupted repression of AFP transcription. These findings support a model of cooperativity between p53 and TGF-beta effectors in chromatin modification and transcription repression of an oncodevelopmental tumor marker gene.

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Last modification of this entry: Oct. 6, 2010

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