Identification of miRNA targets in breast cancer cells (Ago2-IP)

miRNAs regulate mRNA stability and translation through the action of the RNAi-induced silencing complex. In this study, we systematically identified endogenous miRNA target genes by using AGO2 immunoprecipitation (AGO2-IP) and microarray analyses in two breast cancer cell lines, MCF7 and MDA-MB-231, representing luminal and basal-like breast cancer, respectively. The expression levels of ~70% of the AGO2-IP mRNAs were increased by DROSHA or DICER1 knockdown. In addition, integrated analysis of miRNA expression profiles, mRNA-AGO2 interaction, and the 3'-UTR of mRNAs revealed that >60% of the AGO2-IP mRNAs were putative targets of the fifty most abundantly expressed miRNAs. To identify mRNAs associated with AGO2, cell lysate was precleaned with control IgG and immunoprecipitated with anti-human Ago2 (Clone 2E12-1C9, Abnova). Total RNA from cell lysate or coimmunoprecipitated with AGO2 was extracted with Trizol and subjected to microarray analysis, with three biological repeats for each experimental condition.