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Identification of a retinoic acid-inducible gene I from grass carp (Ctenopharyngodon idella) and expression analysis in vivo and in vitro

Yang, Chunrong, Su, Jianguo, Huang, Teng, Zhang, Rongfang, Peng, Limin
Fish & shellfish immunology 2011 v.30 no.3 pp. 936-943
Ctenopharyngodon idella, DNA viruses, Reoviridae, amino acids, caspases, complementary DNA, fish, gene expression, gene expression regulation, genes, immune response, interferons, isoelectric point, liver, messenger RNA, molecular weight, polypeptides, potassium, restriction endonucleases, retinoic acid, reverse transcriptase polymerase chain reaction, spleen, tissues
RIG-I (retinoic acid inducible gene-I) is a key mediator of antiviral immunity, able to couple detection of infection by RNA and DNA viruses to the induction of interferons. In the present study, a RIG-I gene from grass carp Ctenopharyngodon idella (CiRIG-I) was isolated and characterized. The full-length cDNA of CiRIG-I was of 3198 bp and encoded a polypeptide of 947 amino acids with an estimated molecular mass of 108,730 Da and a predicted isoelectric point of 5.85, including six main overlapping structural domains: two CARDs (caspase activation and recruitment domain), one ResIII (conserved restriction domain of bacterial type III restriction enzyme), one DEXDc (DEAD/DEAH box helicase domain), one HELICc (helicase superfamily c-terminal domain) and one RD (regulatory domain). The CiRIG-I mRNA was widespread expression in the tested 15 tissues by semi-quantitative RT-PCR (sqRT-PCR) assay. The CiRIG-I expressions in spleen and liver were significantly induced following grass carp reovirus (GCRV) infection. CiRIG-I mRNA expression was rapidly and significantly up-regulated in vitro after GCRV infection, and the CiRIG-I transcripts were also significantly enhanced in vitro post the synthetic double stranded RNA polyinosinic–polycytidylic potassium salt (poly(I:C)) stimulation. These results collectively suggested that CiRIG-I was an inducible protein, involved in the antiviral innate immune defense to GCRV in grass carp, and laid the foundation for the further mechanism research of RIG-I in fishes.