The normally imprinted insulin-like growth factor II (IGF2) gene is aberrantly upregulated in a variety of human malignancies, yet the mechanisms underlying this dysregulation are still poorly defined. In this report, we used a CRISPR Cas9-guided chromatin immunoprecipitation assay to characterize the molecular components that participate in the control of IGF2 gene expression in human tumor cells. We found that miR483, an oncogenic intronic miRNA, binds to the most upstream imprinted IGF2 promoter, P2. Ectopic expression of miR483 induced upregulation of IGF2 expression, in parallel with an increase in tumor cell proliferation, migration, invasion, and tumor colony formation. miR483 induced loss of IGF2 imprinting by altering the epigenotype at P2, with reduction in histone H3K27 methylation and a decrease in chromatin binding of two imprinting regulatory factors, CTCF and SUZ12. This study identifies a new role for miR483 in the regulation of IGF2 gene expression through the alteration of the promoter epigenotype.
Keywords: IGF2 imprinting; allelic expression; epigenetics; histone K27 methylation; tumor.