Fig. 1.

Nuclear and cytoplasmic fractionations indicate that mature miRNAs are shuttled through the nucleus. The nuclear (Nc) and cytoplasmic (Cy) fractionations of HCT116 parental cells (A) or HCT116 transfected with a 21-mer (si-21) or 25/27-mer (si-27) siRNA (B) with or without 6 h of LMB treatment (20 ng/mL). The RNA fractions were electrophoresed in a denaturing acrylamide gel, blotted onto a nylon membrane, and hybridized with probes complementary to mir16 or mir29b. Both the premiRNAs (pre-mir16 and pre-mir29b) and the corresponding guide sequences (mir16 and mir29b) are shown. Probes specific for U6 snRNA (nuclear) and tRNA (cytoplasmic) were used to determine the relative purities of the fractions.