MKP-1 mRNA Stabilization and Translational Control by RNA-Binding Proteins HuR and NF90

Abstract

The mitogen-activated protein (MAP) kinase phosphatase 1 (MKP-1) plays a major role in dephosphorylating and thereby inactivating the MAP kinases extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38. Here, we examine the posttranscriptional events underlying the robust MKP-1 induction by oxidants in HeLa cells. H₂O₂ treatment potently stabilized the MKP-1 mRNA and increased the association of MKP-1 mRNA with the translation machinery. Four RNA-binding proteins (RNA-BPs) that influence mRNA turnover and/or translation (HuR, NF90, TIAR, and TIA-1) were found to bind to biotinylated transcripts spanning the MKP-1 AU-rich 3′ untranslated region. By using ribonucleoprotein immunoprecipitation analysis, we showed that H₂O₂ treatment increased the association of MKP-1 mRNA with HuR and NF90 and decreased its association with the translational repressors TIAR and TIA-1. HuR or NF90 silencing significantly diminished the H₂O₂-stimulated MKP-1 mRNA stability; HuR silencing also markedly decreased MKP-1 translation. In turn, lowering MKP-1 expression in HuR-silenced cultures resulted in substantially elevated phosphorylation of JNK and p38 after H₂O₂ treatment. Collectively, MKP-1 upregulation by oxidative stress is potently influenced by increased mRNA stability and translation, mediated at least in part by the RNA-BPs HuR and NF90.