Signal transduction pathways regulate gene expression in part by modulating the stability of specific mRNAs. For example, the mitogen-activated protein kinase (MAPK) p38 pathway mediates stabilization of tumor necrosis factor alpha (TNF-alpha) mRNA in myeloid cells stimulated with bacterial lipopolysaccharide (LPS). The zinc finger protein tristetraprolin (TTP) is expressed in response to LPS and regulates the stability of TNF-alpha mRNA. We show that stimulation of RAW264.7 mouse macrophages with LPS induces the binding of TTP to the TNF-alpha 3' untranslated region. The p38 pathway is required for the induction of TNF-alpha RNA-binding activity and for the expression of TTP protein and mRNA. Following stimulation with LPS, TTP is expressed in multiple, differentially phosphorylated forms. We present evidence that phosphorylation of TTP is mediated by the p38-regulated kinase MAPKAPK2 (MAPK-activated protein kinase 2). Our findings demonstrate a direct link between a specific signal transduction pathway and a specific RNA-binding protein, both of which are known to regulate TNF-alpha gene expression at a posttranscriptional level.
Mol Cell Biol
6461 - 6469
3' Untranslated Regions, Animals, Cell Extracts, Cell Line, DNA-Binding Proteins, Humans, Immediate-Early Proteins, Intracellular Signaling Peptides and Proteins, Kinetics, Lipopolysaccharides, MAP Kinase Signaling System, Macromolecular Substances, Mice, Mitogen-Activated Protein Kinases, Phosphorylation, Protein Processing, Post-Translational, Protein-Serine-Threonine Kinases, RNA Stability, RNA, Messenger, RNA-Binding Proteins, Transcription, Genetic, Tristetraprolin, Tumor Necrosis Factor-alpha, p38 Mitogen-Activated Protein Kinases