Hedgehog (Hh) signaling plays many important roles in developmental processes and cancers. Smoothened (Smo) is an important signal transducer in the Hh pathway, and its expression is tightly regulated by several different post-transcriptional mechanisms. However, whether microRNAs (miRNAs) are involved in Smo regulation is still unclear. Here, we found that miR-5 acts as a suppressor of the Hh pathway by targeting Smo. Through in vivo sensor assay and in vitro luciferase assay, we found that miR-5 downregulates Smo through directly binding to its 3'UTR. Moreover, our data indicated Costal-2 (Cos2) and Fused (Fu) do not play a role in the reduction of Smo mediated by miR-5. Furthermore, we determined that miR-5 not involved in Notch or Dpp signaling pathways by detecting target gene expression. Together, our results indicate that miR-5 can specifically suppress Hh signaling by directly targeting Smo in Drosophila.
