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Cooperation between phosphorylation and acetylation processes in transcriptional control
E Espinos1, A Le Van Thaï, C Pomiès
1Laboratoire de Biologie Moléculaire Eucaryote, CNRS UPR 9006, 31062 Toulouse Cedex, France.
Abstract:
We previously reported that the activation of the M promoter of the human choline acetyltransferase (ChAT) gene by butyrate and trapoxin in transfected CHP126 cells is blocked by PD98059, a specific mitogen-activated protein kinase kinase (MEK) inhibitor (E. Espinos and M. J. Weber, Mol. Brain Res. 56:118-124, 1998). We now report that the transcriptional effects of histone deacetylase inhibitors are mediated by an H7-sensitive serine/threonine protein kinase. Activation of the ChAT promoter by butyrate and trapoxin was blocked by 50 microM H7 in both transient- and stable-transfection assays. Overexpression of p300, a coactivator protein endowed with histone acetyltransferase activity, stimulated the ChAT promoter and had a synergistic effect on butyrate treatment. These effects were blocked by H7 and by overexpressed adenovirus E1A 12S protein. Moreover, both H7 and PD98059 suppressed the activation of the Rous sarcoma virus (RSV) and simian virus 40 promoters by butyrate in transfection experiments. Similarly, the induction of the cellular histone H1(0) gene by butyrate in CHP126 cells was blocked by H7 and by PD98059. Previous data (L. Cuisset, L. Tichonicky, P. Jaffray, and M. Delpech, J. Biol. Chem. 272:24148-24153, 1997) showed that the induction of the H1(0) gene by butyrate is blocked by okadaic acid, an inhibitor of protein phosphatases. We now show that the activation of the ChAT and RSV promoters by butyrate in transfected CHP126 cells is also blocked by 200 nM okadaic acid. Western blotting and in vivo metabolic labeling experiments showed that butyrate has a biphasic effect on histone H3 phosphorylation, i.e., depression for up to 16 h followed by stimulation. The data thus strongly suggest that the transcriptional effects of histone deacetylase inhibitors are mediated through the activation of MEK1 and of an H7-sensitive protein kinase in addition to protein phosphatases.
Insights
Histone deacetylase inhibitors like butyrate activate gene transcription via MEK1 and an H7-sensitive kinase, alongside protein phosphatases. This pathway influences choline acetyltransferase (ChAT) and histone H1(0) gene expression.
Area of Science:
- Molecular Biology
- Gene Regulation
- Epigenetics
Background:
- Histone deacetylase (HDAC) inhibitors, such as butyrate, are known to modulate gene expression.
- Previous studies indicated that mitogen-activated protein kinase kinase (MEK) inhibitors block HDAC inhibitor-induced activation of the choline acetyltransferase (ChAT) promoter.
Purpose of the Study:
- To elucidate the signaling pathways mediating the transcriptional effects of HDAC inhibitors.
- To identify the specific kinases and phosphatases involved in the regulation of ChAT and other gene promoters by HDAC inhibitors.
Main Methods:
- Transient and stable transfection assays using reporter constructs for ChAT, Rous sarcoma virus (RSV), and simian virus 40 (SV40) promoters.
- Inhibition studies using specific kinase (H7, PD98059) and phosphatase (okadaic acid) inhibitors.
- Overexpression of coactivator protein p300 and adenovirus E1A 12S protein.
- Western blotting and in vivo metabolic labeling to assess histone H3 phosphorylation.
Main Results:
- Activation of the ChAT promoter by butyrate and trapoxin was inhibited by H7, a serine/threonine protein kinase inhibitor.
- Overexpression of p300 enhanced ChAT promoter activity, an effect blocked by H7.
- Both H7 and PD98059 (MEK inhibitor) suppressed butyrate-induced activation of ChAT, RSV, and SV40 promoters.
- Butyrate's induction of the histone H1(0) gene was blocked by H7 and PD98059, and also by okadaic acid (phosphatase inhibitor).
- Butyrate exhibited a biphasic effect on histone H3 phosphorylation: initial depression followed by stimulation.
Conclusions:
- The transcriptional effects of HDAC inhibitors are mediated by the activation of MEK1 and an H7-sensitive protein kinase.
- Protein phosphatases also play a role in this signaling pathway.
- These findings reveal a complex signaling network involving kinases and phosphatases in HDAC inhibitor-mediated gene regulation.