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Nature. 2008 Sep 25;455(7212):552-6. doi: 10.1038/nature07310. Epub 2008 Sep 14.

E2F1 represses beta-catenin transcription and is antagonized by both pRB and CDK8.

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1
Laboratory of Molecular Oncology, Massachusetts General Hospital Cancer Center and Harvard Medical School, 13th Street, Building 149, Charlestown, Massachusetts 02129, USA.

Abstract

The E2F1 transcription factor can promote proliferation or apoptosis when activated, and is a key downstream target of the retinoblastoma tumour suppressor protein (pRB). Here we show that E2F1 is a potent and specific inhibitor of beta-catenin/T-cell factor (TCF)-dependent transcription, and that this function contributes to E2F1-induced apoptosis. E2F1 deregulation suppresses beta-catenin activity in an adenomatous polyposis coli (APC)/glycogen synthase kinase-3 (GSK3)-independent manner, reducing the expression of key beta-catenin targets including c-MYC. This interaction explains why colorectal tumours, which depend on beta-catenin transcription for their abnormal proliferation, keep RB1 intact. Remarkably, E2F1 activity is also repressed by cyclin-dependent kinase-8 (CDK8), a colorectal oncoprotein. Elevated levels of CDK8 protect beta-catenin/TCF-dependent transcription from inhibition by E2F1. Thus, by retaining RB1 and amplifying CDK8, colorectal tumour cells select conditions that collectively suppress E2F1 and enhance the activity of beta-catenin.

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PMID:
18794899
PMCID:
PMC3148807
DOI:
10.1038/nature07310
[Indexed for MEDLINE]
Free PMC Article

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