A Phosphorylation Switch Regulates the Transcriptional Activation of Cell Cycle Regulator p21 by Histone Deacetylase Inhibitors

Elisabeth Simboeck,Anna Sawicka,Gordin Zupkovitz,Silvia Senese,Stefan Winter,Franck Dequiedt,Egon Ogris,Luciano Di Croce,Susanna Chiocca,Christian Seiser

doi:10.1074/jbc.m110.184481

Abstract

Histone deacetylase inhibitors induce cell cycle arrest and apoptosis in tumor cells and are, therefore, promising anti-cancer drugs. The cyclin-dependent kinase inhibitor p21 is activated in histone deacetylase (HDAC) inhibitor-treated tumor cells, and its growth-inhibitory function contributes to the anti-tumorigenic effect of HDAC inhibitors. We show here that induction of p21 by trichostatin A involves MAP kinase signaling. Activation of the MAP kinase signaling pathway by growth factors or stress signals results in histone H3 serine 10 phosphorylation at the p21 promoter and is crucial for acetylation of the neighboring lysine 14 and recruitment of activated RNA polymerase II in response to trichostatin A treatment. In non-induced cells, the protein phosphatase PP2A is associated with the p21 gene and counteracts its activation. Induction of p21 is linked to simultaneous acetylation and phosphorylation of histone H3. The dual modification mark H3S10phK14ac at the activated p21 promoter is recognized by the phospho-binding protein 14-3-3ζ, which protects the phosphoacetylation mark from being processed by PP2A. Taken together we have revealed a cross-talk of reversible phosphorylation and acetylation signals that controls the activation of p21 by HDAC inhibitors and identify the phosphatase PP2A as chromatin-associated transcriptional repressor in mammalian cells.

Highlights

Important roles in the regulation of chromatin accessibility and gene expression
Activation of p21 Expression by histone deacetylase (HDAC) Inhibition Requires a Second Signal—In this study we intended to analyze the molecular mechanisms regulating the activation of the p21 gene in response to HDAC inhibitor treatment
Mitogenactivated Protein (MAP) Kinase Activation Sensitizes Resting Cells to HDAC Inhibitor Treatment—In this report we analyzed in details the mechanisms responsible for the activation of the cyclin-dependent kinase (CDK) inhibi

Summary

A Phosphorylation Switch Regulates the Activation of p21

P21 is implicated in terminal differentiation, replicative senescence, and protection from p53-dependent and -independent apoptosis [18, 19]. P21, which is usually considered to act as a tumor suppressor, might act as an oncogene [30] Along this line, a tumor promoting activity of p21 was recently shown in different mouse tumor models [31, 32]. We show that histone H3 phosphorylation at the p21 promoter is indispensable for the activation of the p21 gene by HDAC inhibitors. The activation of stress or mitogen-activated signaling cascades in concert with HDAC inhibition leads to simultaneous Ser-10 phosphorylation and Lys-14 acetylation (phosphoacetylation) of histone H3 at the p21 promoter. We identify mitogen- and stress-activated kinase 1 (MSK1) to be one of the kinases responsible for histone H3 phosphorylation and demonstrate its importance for p21 gene activation. We demonstrate that recognition of the phosphoacetylation mark by the adaptor protein 143-3␨ is important for p21 activation, and this might be in part due to protection of the mark from dephosphorylation by PP2A

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION