Figure 4.
5′-extended pre-miRNAs are exported by XPO1. (A) Northern blot analyses of miR-HSUR4-3p and endogenous miR-16, U6 and tRNAlys in the nuclear and cytoplasmic fractions from HCT116 cells with protein knockout as indicated. WT, +15 or +30 nt 5′-extended pre-miR-HSUR4 were expressed from transfected plasmids. U6 and tRNAlys served as nuclear and cytoplasmic markers, respectively. C: cytoplasm; N: nucleus. (B) Upper panel: Northern blot analyses of miR-HSUR4-3p, miR-142-3p, miR-344 and EBER1 in 293T cells with or without PHAX knockdown. Total RNA was extracted from 293T cells transfected with siCtrl or siPHAX for 48 h, then co-transfected with plasmids encoding the four RNAs. Quantitations of relative mature miRNA levels (mean ± standard deviation) were derived from three independent experiments. siCtrl: negative control siRNA; siPHAX: specific siRNA for PHAX. Bottom panel: Western blot showing knockdown of PHAX, with GAPDH as loading control.