Induction of <i>VEGFA</i> mRNA translation by CoCl₂ mediated by HuR

Vascular endothelial growth factor (VEGF) A is a master regulator of neovascularization and angiogenesis. VEGFA is potently induced by hypoxia and by pathological conditions including diabetic retinopathy and tumorigenesis. Fine-tuning of VEGFA expression by different stimuli is important for maintaining tissue vascularization and organ homeostasis. Here, we tested the effect of the hypoxia mimetic cobalt chloride (CoCl₂) on VEGFA expression in human cervical carcinoma HeLa cells. We found that CoCl₂ increased the levels of <i>VEGFA</i> mRNA and VEGFA protein without affecting <i>VEGFA</i> mRNA stability. Biotin pulldown analysis to capture the RNA-binding proteins (RBPs) bound to <i>VEGFA</i> mRNA followed by mass spectrometry analysis revealed that the RBP HuR [human antigen R, a member of the embryonic lethal abnormal vision (ELAV) family of proteins], interacts with <i>VEGFA</i> mRNA. <i>VEGFA</i> mRNA-tagging experiments showed that exposure to CoCl₂ increases the interaction of HuR with <i>VEGFA</i> mRNA and promoted the colocalization of HuR and the distal part of the <i>VEGFA</i> 3′-untranslated region (UTR) in the cytoplasm. We propose that under hypoxia-like conditions, HuR enhances <i>VEGFA</i> mRNA translation.