Effect of miR-155 on type I interferon response in Epithelioma papulosum cyprini cells

MicroRNA-155 (miRNA-155) is known to play an important role in the regulation of innate and adaptive immune responses in mammals. However, no information is available on the role of miRNA-155 in relation to type I interferon (IFN) responses in fish cells. In the present study, we found that the protein inhibitor of activated STAT 4a (PIAS4a) gene of fathead minnow (Pimephales promelas) was a target of miR-155, which was verified by the inhibitory activity of miR-155 in the expression of reporter gene harboring 3'UTR of PIAS4a of EPC cells. Furthermore, cells over-expressing miR-155 showed a significantly higher type I IFN response after polyinosinic-polycytidylic acid (poly I:C) stimulation, suggesting the targeting of PIAS4a in EPC cells by miR-155 can be a cause of the up-regulation of type I IFN, and miR-155 can act as an antiviral factor. However, as the targeting PIAS4a might not be the sole cause of the type I IFN up-regulation by miR-155, further studies on the uncovering of miR-155 target genes that are involved in type I IFN responses in fish are required.