AUF1/hnRNP D represses expression of VEGF in macrophages

Vascular endothelial growth factor (VEGF) is a regulator of vascularization in development and is a key growth factor in tissue repair. In disease, VEGF contributes to vascularization of solid tumors and arthritic joints. This study examines the role of the mRNA-binding protein AUF1/heterogeneous nuclear ribonucleoprotein D (AUF1) in VEGF gene expression. We show that overexpression of AUF1 in mouse macrophage-like RAW-264.7 cells suppresses endogenous VEGF protein levels. To study 3' untranslated region (UTR)-mediated regulation, we introduced the 3' UTR of VEGF mRNA into a luciferase reporter gene. Coexpression of AUF1 represses VEGF-3' UTR reporter expression in RAW-264.7 cells and in mouse bone marrow-derived macrophages. The C-terminus of AUF1 contains arginine-glycine-glycine (RGG) repeat motifs that are dimethylated. Deletion of the RGG domain of AUF1 eliminated the repressive effects of AUF1. Surprisingly, expression of an AUF1-RGG peptide reduced endogenous VEGF protein levels and repressed VEGF-3' UTR reporter activity in RAW-264.7 cells. These findings demonstrate that AUF1 regulates VEGF expression, and this study identifies an RGG peptide that suppresses VEGF gene expression.