Fig 3.

MiR-107 post-transcriptionally down-regulates DICER1 expression by directly targeting its 3′-UTR. (A) The target site of miR-107 in DICER1 3′-UTR is conserved among mammalian species (shown in white). (B) Predicted duplex formation between miR-107 and the targeted DICER1 3′-UTR. The DICER1 3′-UTR mutant is identical to the wild-type, except that it had four point substitutions (red) disrupting pairing to miR-107 seed. (C) pGL3-DICER1 3′-UTR reporter plasmid in which the luciferase coding sequence had been fused to the 3′-UTR of DICER1 was co-transfected into HERK 293T cells with pcDNA3.1 or pcDNA3.1–miR-107. Luciferase activity was normalized relative to a simultaneously transfected Renilla expression plasmid. The 3′-UTR-Mut indicates the introduction of alterations into the seed complementary sites shown in Figure 2B. N = 3; error bars represent S.E.M. P-values obtained using a one-sided Student’s t-test. P < 0.05 versus cells transfected with control. (D) Western blots of DICER1 in SGC-7901 or MKN-45 cells after miR-107 sponge or control retrovirus infection. β-Actin antibody was used as a internal control. The level of DICER1 protein expression level was indicated by the ratio of DICER1/actin (bottom). Representative of three experiments with similar results.