title: Activation of the coactivator four-and-a-half-LIM-only protein FHL2 and the c-fos promoter through inhibition of protein phosphatase 2A.
abstract: Previous studies have demonstrated that the serine/threonine protein phosphatase 2A (PP2A) can modulate the transcriptional activity of several sequence-specific DNA-binding proteins. However, less is known about the effect of PP2A on the activities of general transcription factors and transcriptional coregulators. Here we describe that the activity of a general coactivator, the four-and-a-half-LIM-only protein 2 (FHL2), is regulated in a PP2A-dependent manner. Specific inhibition of PP2A by simian virus 40 (SV40) small t-antigen (st-ag) stimulated the intrinsic transcriptional activity of FHL2 more than 10-fold, while a st-ag mutant unable to bind PP2A had no effect. Overexpression of the B56 subunits alpha, beta, and gamma1 of PP2A impaired the induction of FHL2 by st-ag. FHL2 functioned as a coactivator for CREB-mediated transcription, and inactivation of PP2A further increased FHL2-induced CREB-directed transcription. Overexpression of FHL2 readily enhanced the transcription of the luciferase reporter gene driven by the c-fos promoter, and inhibition of PP2A further stimulated FHL2-induced transactivation of this promoter. These results suggest that dephosphorylation of the general coactivator FHL2 may represent a novel mechanism by which PP2A modulates the transcription of FHL2-responsive genes.
authors.affiliation: Department of Biochemistry, Section for Molecular Genetics, Institute of Medical Biology, University of Tromsø, Norway.
authors.forename: Mona
authors.initials: M
authors.lastname: Johannessen
authors.forename: Petter Angell
authors.initials: PA
authors.lastname: Olsen
authors.forename: Bjarne
authors.initials: B
authors.lastname: Johansen
authors.forename: Ole Morten
authors.initials: OM
authors.lastname: Seternes
authors.forename: Ugo
authors.initials: U
authors.lastname: Moens
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D005576:Colforsin / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D016762:Genes, fos / Q000187:drug effects / Q000235:genetics*; D018398:Homeodomain Proteins / Q000187:drug effects / Q000378:metabolism*; D060850:LIM-Homeodomain Proteins; D008156:Luciferases / Q000235:genetics; D051379:Mice; D009124:Muscle Proteins; D016297:Mutagenesis, Site-Directed; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010957:Plasmids; D011401:Promoter Regions, Genetic; D054648:Protein Phosphatase 2; D021122:Protein Subunits / Q000037:antagonists & inhibitors; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects / Q000235:genetics; D011994:Recombinant Proteins / Q000187:drug effects / Q000235:genetics; D014157:Transcription Factors / Q000187:drug effects / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; C491382:Fhl2 protein, mouse; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D009124:Muscle Proteins; D021122:Protein Subunits; D016760:Proto-Oncogene Proteins c-fos; D011994:Recombinant Proteins; D014157:Transcription Factors; D005576:Colforsin; D008156:Luciferases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2