Up-Regulation of P-TEFb by the MEK1-Extracellular Signal-Regulated Kinase Signaling Pathway Contributes to Stimulated Transcription Elongation of Immediate Early Genes in Neuroendocrine Cells

Abstract

The positive elongation factor P-TEFb appears to function as a crucial C-terminal-domain (CTD) kinase for RNA polymerase II (Pol II) transcribing immediate early genes (IEGs) in neuroendocrine GH4C1 cells. Chromatin immunoprecipitation indicated that in resting cells Pol II occupied the promoter-proximal regions of the c-fos and junB genes, together with the negative elongation factors DSIF and NELF. Thyrotropin-releasing hormone (TRH)-induced recruitment of positive transcription elongation factor b (P-TEFb) abolished the pausing of Pol II and enhanced phosphorylation of CTD serine 2, resulting in transcription elongation. In addition, P-TEFb was essential for splicing and 3′-end processing of IEG transcripts. Importantly, the MEK1-extracellular signal-regulated kinase (ERK) signaling pathway activated by TRH up-regulated nuclear CDK9 and CDK9/cyclinT1 dimers (i.e., P-TEFb), facilitating the recruitment of P-TEFb to c-fos and other IEGs. Thus, in addition to established gene transcription control via promoter response elements, the MEK1-ERK signaling pathway controls transcription elongation by Pol II via the up-regulation of nuclear CDK9 integrated into P-TEFb.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/ .

ACKNOWLEDGMENTS

We are very grateful to T. Wada and R. Young for providing us the GST-CTD construct.

This investigation was supported in part by the Swiss National Science Foundation grant 3100A0-102147 and by the Fondation pour Recherches Médicales.