E2F1 Modulates p38 MAPK Phosphorylation via Transcriptional Regulation of ASK1 and Wip1*

The E2F family of transcription factors regulates a diverse array of cellular functions, including cell proliferation, cell differentiation, and apoptosis. Recent studies indicate that E2F can also regulate transcription of upstream components of signal transduction pathways. We show here that E2F1 modulates the activity of the p38 MAPK pathway via E2F1-induced transient up-regulation of p38 MAPK phosphorylation. The mechanism by which E2F1 modulates p38 MAPK phosphorylation involves transcriptional induction of the kinase ASK1, a member of the MAPKKK family that phosphorylates p38 MKKs. Subsequent E2F-dependent down-regulation of the p38 signaling pathway is achieved through E2F-induced up-regulation of Wip1, a phosphatase that dephosphorylates and inactivates p38. Both ASK1 and Wip1 are essential mediators of the E2F-p38 connection: knock down of ASK1 inhibits E2F1-induced phosphorylation of p38, whereas knock down of Wip1 prolongs E2F1-induced p38 phosphorylation. Furthermore, Wip1 knock down enhances E2F1-induced apoptosis. Therefore, our data reveal a novel link between a central signaling pathway and the transcription factor E2F and identify Wip1 as a modulator of E2F1-induced apoptosis.

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