title: MAPK-induced Ser727 phosphorylation promotes SUMOylation of STAT1.
abstract: STAT1 (signal transducer and activator of transcription 1) is a critical mediator of IFN-gamma (interferon-gamma)-induced gene responses, and its function is regulated through phosphorylation of Tyr701 and Ser727. MAPK (mitogen-activated protein kinase) pathways mediate phosphorylation of Ser727 in response to microbial infections, stress stimuli and growth factors. Recently, STAT1 was found to become modified by PIAS (protein inhibitor of activated STAT)-mediated SUMO-1 (small ubiquitin-related modifier-1) conjugation at Lys703, but the regulation of this modification is largely unknown. Here, we have investigated the role of MAPK-induced Ser727 phosphorylation in regulation of STAT1 SUMOylation. Activation of the p38MAPK pathway by upstream activating kinase, MKK6 (MAPK kinase-6) or osmotic stress enhanced the SUMOylation of STAT1, which was counteracted by the p38MAPK inhibitor SB202190 or by dominant-negative p38MAPK. Activation of the ERK1/2 (extracellular-signal-regulated kinase 1/2) pathway by Raf-1 also enhanced Ser727 phosphorylation and SUMOylation of STAT1, and this induction was counteracted by PD98059 inhibitor. Mutation of Ser727 to alanine abolished the p38MAPK-induced SUMOylation. Furthermore, S727D and S727E mutations, which mimic the phosphorylation of Ser727, enhanced the basal SUMOylation of STAT1 and interaction between PIAS1 and STAT1. Taken together, these results identify Ser727 phosphorylation as a regulator of STAT1 SUMOylation and highlight the central role of Ser727 in co-ordination of STAT1 functions in cellular responses.
authors: Institute of Medical Technology, University of Tampere, FIN-33014 Tampere, Finland.
authors: Sari
authors: S
authors: Vanhatupa
authors: Daniela
authors: D
authors: Ungureanu
authors: Maija
authors: M
authors: Paakkunainen
authors: Olli
authors: O
authors: Silvennoinen
mesh_terms: D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D008239:Lysine / Q000737:chemistry; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D050794:STAT1 Transcription Factor / Q000737:chemistry*; D025842:SUMO-1 Protein / Q000378:metabolism*; D012694:Serine / Q000737:chemistry*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D025842:SUMO-1 Protein; D012694:Serine; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D008239:Lysine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one