title: ERK2- and p90(Rsk2)-dependent pathways regulate the CCAAT/enhancer-binding protein-beta interaction with serum response factor.
abstract: The serum response element (SRE) of the c-fos promoter is a convergence point for mitogenic signaling pathways. Several transcription factors regulate SRE, including serum response factor (SRF), ternary complex factors, and CCAAT/enhancer-binding protein-beta (C/EBPbeta). C/EBPbeta can interact with both SRF and the ternary complex factor family member Elk-1, but only in response to activated Ras. Transactivation of the SRE by C/EBPbeta is also greatly stimulated by Ras. The Ras effectors that signal to C/EBPbeta are unknown. In this report, we demonstrate that a consensus MAPK site in C/EBPbeta is necessary for Ras stimulation of both C/EBPbeta-SRF interaction and transactivation of the SRE by C/EBPbeta. To dissect signaling pathways activated downstream of Ras, different Ras effector constructs were analyzed. We show that activated forms of Raf and phosphatidylinositol 3-kinase stimulate C/EBPbeta-SRF interaction. We also show a novel selectivity for the MAPK family member ERK2, where dominant-negative ERK2, but not dominant-negative ERK1, blocks Ras stimulation of C/EBPbeta-SRF interaction. In addition, recombinant C/EBPbeta protein is phosphorylated by ERK2, but not by ERK1, in vitro. Finally, we demonstrate a requirement for p90(Rsk2) in regulation of C/EBPbeta-SRF interaction. These data show that multiple Ras effectors are required to regulate C/EBPbeta and SRF association.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hanlon
authors.forename: T W
authors.initials: TW
authors.lastname: Sturgill
authors.forename: L
authors.initials: L
authors.lastname: Sealy
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D005799:Genes, Dominant; D015151:Immunoblotting; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism*; D026362:Serum Response Factor / Q000378:metabolism*; D015398:Signal Transduction; D013912:Threonine / Q000737:chemistry; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection; D050807:ets-Domain Protein Elk-1
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D004268:DNA-Binding Proteins; C494113:Elk1 protein, mouse; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D026362:Serum Response Factor; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D013912:Threonine; D019869:Phosphatidylinositol 3-Kinases; D019893:Ribosomal Protein S6 Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases