Coexpression of an intronic microRNA and its host gene reveals a potential role for miR-483-5p as an IGF2 partner

MicroRNAs (miRNAs) are endogenous noncoding RNAs that downregulate gene expression by inhibiting translation or promoting mRNA degradation. Although over one-third of miRNAs are located within the intronic regions of transcription units, the expression of such intron-derived (or intronic) miRNAs and their relationship with their host gene remain a mystery. Here, we show that miR-483-5p, which is located within the second intron of the insulin-like growth factor (Igf2) gene, is downregulated in mouse Hepa1-6 cells in a direct correlation with the Igf2 transcript by chromeceptin, an inhibitor of Igf2 at the transcriptional level. Furthermore, miR-483-5p overexpression and knockdown regulates the suppressor of cytokine signalling 3 (Socs3) and Igf2 mRNAs, respectively. Finally, Socs3, a key putative leptin-resistant factor in obesity, is identified as a direct target of miR-483-5p. These data suggest that miR-483-5p can be coexpressed together with its host gene, Igf2, and revealed the link between this miRNA and the IGF2 growth factor. In addition, these observations not only provide supporting evidence for the codependent expression of intronic miRNAs and their host genes in vitro, but also give insight into the role of miR-483-5p in metabolism regulation and tumourigenesis. (C) 2010 Elsevier Ireland Ltd. All rights reserved.