title: An interplay between the p38 MAPK pathway and AUBPs regulates c-fos mRNA stability during mitogenic stimulation.
abstract: Mitogen-activated protein kinase (MAPK) pathways constitute key regulatory elements linking extracellular stimuli to nuclear gene expression. Immediate-early responsive genes (IEGs) of the activator protein 1 (AP-1) family, such as fos, achieve peak expression levels shortly after cells are stimulated with growth factors and sharply decrease thereafter. Several AU-rich binding proteins (AUBPs), including HuR (Hu-antigen R, Elav-like protein 1, ELAVL1) and KSRP (far upstream element-binding protein 2, KHSRP) bind to a fos AU-rich element (ARE) present in the 3'-UTR (untranslated region) of fos mRNA regulating its stability by a still poorly defined mechanism. We show in the present study that, whereas HuR binds and stabilizes transcribed reporter mRNAs bearing the fos 3'-UTR, KSRP counteracts this effect. Furthermore, we found that fos mRNA stability and HuR phosphorylation status are dependent on the activity of p38 MAPK in both epithelial cells and fibroblasts upon proliferative stimulation. Analysing PPI (protein-protein interaction) networks, we performed a thorough query of interacting proteins for p38 MAPKs, HuR and other AUBPs upon growth factor stimulation. This revealed novel HuR interactors including inhibitors of protein phosphatase 2 (PP2A) activity. Over-expression of two of these interactors, pp32 and APRIL (acidic leucine-rich nuclear phosphoprotein 32 family member B, ANP32B) and pharmacological inhibition of PP2A stabilized a fos reporter mRNA. Our results indicate that p38 MAPK regulates fos mRNA decay by affecting the state of phosphorylation of HuR while controlling yet to be fully elucidated PP regulatory networks.
authors.affiliation: *LFBM-DFBMC, Departamento de Fisiología y Biología Molecular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (FCEN-UBA), Buenos Aires C1428EHA, Argentina.
authors.forename: Maria Sol
authors.initials: MS
authors.lastname: Degese
authors.affiliation: *LFBM-DFBMC, Departamento de Fisiología y Biología Molecular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (FCEN-UBA), Buenos Aires C1428EHA, Argentina.
authors.forename: Tamara
authors.initials: T
authors.lastname: Tanos
authors.affiliation: *LFBM-DFBMC, Departamento de Fisiología y Biología Molecular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (FCEN-UBA), Buenos Aires C1428EHA, Argentina.
authors.forename: Julian
authors.initials: J
authors.lastname: Naipauer
authors.affiliation: ‡DBMS, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada, N1G 2W1.
authors.forename: Tim
authors.initials: T
authors.lastname: Gingerich
authors.affiliation: §Proteomics Core Facility, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Diego
authors.initials: D
authors.lastname: Chiappe
authors.affiliation: ║Département de Biologie Cellulaire, Université de Genève, Sciences 3, CH-1211 Genève 4, Switzerland.
authors.forename: Pablo
authors.initials: P
authors.lastname: Echeverria
authors.affiliation: ‡DBMS, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada, N1G 2W1.
authors.forename: Jonathan
authors.initials: J
authors.lastname: LaMarre
authors.affiliation: ¶Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD 20892-4330, U.S.A.
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
authors.affiliation: *LFBM-DFBMC, Departamento de Fisiología y Biología Molecular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (FCEN-UBA), Buenos Aires C1428EHA, Argentina.
authors.forename: Omar A
authors.initials: OA
authors.lastname: Coso
mesh_terms: D020413:3' Untranslated Regions / Q000187:drug effects; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D051959:ELAV Proteins / Q000235:genetics / Q000378:metabolism*; D000067780:ELAV-Like Protein 1; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D008934:Mitogens / Q000494:pharmacology*; D009154:Mutation; D041681:NIH 3T3 Cells; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D016760:Proto-Oncogene Proteins c-fos / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability / Q000187:drug effects*; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; C105789:KHSRP protein, human; C507913:Khsrp protein, mouse; D008934:Mitogens; D047428:Protein Kinase Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D048051:p38 Mitogen-Activated Protein Kinases