Cloning and functional characterization of rat stimulator of interferon genes (STING) regulated by miR-24

Stimulator of interferon (IFN) genes (STING), also known as MPYS/MITA/ERIS/TMEM173, is a recently discovered adaptor protein that functions downstream of RIG-I and upstream of TBK1 and plays an important role in type I interferon (IFN) production. Mammalian STINGs have been isolated from human, mouse, pig, cattle and chimpanzee. In this study, the rat STING cDNA was cloned by degenerate PCR and rapid amplification of 3'-cDNA ends (3'-RACE) strategies. The full-length cDNA of rat STING consists of 1615 bp with a 1140-bp open reading frame (ORF). The predicted protein is composed of 379 amino acids and contains 2 putative transmembrane domains. The amino acid similarities between the STING from rat and other mammals range from 68% to 82%. Real-time quantitative PCR analysis indicated that rat STING mRNA was most abundant in the spleen, pancreas and lymph node. Overexpression of rat STING led to upregulation of IFN-β mRNA expression in IEC-6 cells. Rat STING mRNA was up-regulated when IEC-6 cells were transfected with poly (I:C). In addition, a miR-24 binding site in the 3'UTR of rat STING was identified. We also found that endogenous STING could be regulated post-transcriptionally by miR-24 in IEC-6 cells. These results are of importance to reveal the biological function of STING in rat animal model.