miR-183 can act on the 3'-UTR of PDCD4 directly. (A) The target site of miR-183 in PDCD4 3'UTR is conserved (shown in red) in many species. The PDCD4 3'-UTR mutant is identical to the wild-type, except that it has four point substitutions (red) disrupting pairing to miR-183 seed. (B) and (C) Luciferase assays indicated that miR-183 downregulated the expression of PDCD4 by targeting putative target site. NC RNA, miR-183, and miR-183 inhibitor were cotransfected with a modified pGL-3 control vector containing wild-type PDCD4 3'-UTR or mutant, respectively.