Stress-activated protein kinases (JNK and p38/HOG) are essential for vascular endothelial growth factor mRNA stability

Stability of the vascular endothelial growth factor (VEGF) mRNA is tightly regulated through its 3'-untranslated region (3'-UTR). Here, we demonstrate that VEGF mRNA levels are increased by anisomycin, a strong activator of s tress-activated protein kinases. Hence, VEGF mRNA induction is inhibited by SB202190, an inhibitor of JNK and p38/HOG kinase, Furthermore, VEGF mRNA e xpression is increased in cells that overexpress JNK and p38/HOG; by an inc rease in its stability. We show by two different approaches that anisomycin exerts its effect on the VEGF mRNA 3'-UTR. First, by using an in vitro mRN A degradation assay, the half-life of the VEGF mRNA 3'-UTR region transcrip t was found to be increased when incubated with extracts from anisomycin-tr eated cells; and second, the 3'-UTR was also sufficient to confer mRNA inst ability to the Nhe3 (Na+/H+ exchanger 3) heterologous reporter gene, and an isomycin treatment stabilized the chimeric mRNA (Nhe3 fused to the VEGF mRN A 3'-UTR). This chimeric mRNA is also more stable in cells overexpressing p 38/HOG and JNK that have been stimulated by anisomycin. We show that such r egulation is mediated through an AU-rich region of the 3'-UTR contained wit hin a stable hairpin structure. By RNA electrophoretic mobility shift assay s, we show that this region binds proteins specifically induced by anisomyc in treatment. These findings clearly demonstrate a major role of stress-act ivated protein kinases in the post-transcriptional regulation of VEGF.