Programmed Ago2 coimmunoprecipitates miRNA targets. (A) Lysates from 293S or 293S(c-myc-Ago2) cells transfected with let-7 or GL3.1 siRNAs were incubated with radiolabeled RNAs containing zero, one or three let-7 binding sites, and immunoprecipitated with anti-c-myc beads. T, total lysate (1/10 of immunoprecipitated volume); I, immunoprecipitated complexes. (B) Retention of endogenous miR-124a targets. 293S(Ago2) cells were transfected with miR-124a or GL3.1 siRNAs, lysed, and immunoprecipitated. Transcript levels in total and immunoprecipitated fractions were quantified by RT-QPCR.