Differential Argonaute-2 RNA immunoprecipitation of control cells versus cells overexpressing miR-146a followed by deep sequencing (Ago2 RIP-seq)

We undertook an unbiased approach based on differential Argonaute-2 (Ago2) RNA immunoprecipitation followed by deep sequencing (Ago2 RIP-seq) to unravel the molecular mechanism(s) underlying miR-146a function, namely the relevant mRNA target(s). Ago2 is a crucial protein that engages with both miRNA and its mRNA target(s) in the RISC complex. To overcome the problem of lack of commercially available high affinity antibodies against Ago2, we took advantage of a genetically modified mouse in which endogenous Ago2 is replaced with a N-terminal tagged version of the protein (3xFLAG- 6xHIS), thus allowing stringent purification (i.e., with low unspecific background) of the RNA molecules bound to Ago2 (upon UV-crosslinking), followed by RNA-sequencing. In order to enrich for miR-146a targets, we transduced purified CD3+ T cells (we could not use γδ T cells due to insufficient cell numbers for this approach) with a miR-146a-expressing retrovirus (with~12-fold overexpression of miR-146a). We thereby identified 225 putative mRNAs after differential Ago2-RIP-seq, from which 96 (42,7%) had a predicted miR-146a binding site in their 3’ UTR region. Identification of miR-146a targets in CD3+T lymphocytes based on its differential overexpression