(A). In vitro processing assay for RI-labelled pri-let-7a1. Autoradiographs of gels showing pri-let-7a1 treated with whole cell lysate (WCL) from HEK-293FT cells transfected with GFP, TruB1, mt1, or mt2 (overexpression, left), and TruB1 KD or ctrl (siRNA, right). Dicer KD was used to show the height of pre-let-7a1. (B) RI intensities of (A) were quantified and normalized to ctrl. Relative processing rate of pri-let-7a1 into pre- and mature- are shown. Significance was assessed using 2‐tailed Student's t‐test, < 0.05*. Data information: All experiments were performed in triplicate. Error bars show SD. 