The Function And Mechanism Of MID1 In The Natural Antiviral Immunity

Objective Virus infection is a serious threat to human health.Interferon plays an important antiviral role in vivo as a key component of innate immunity.MID1,a member of the E3 ubiquitin ligase family,plays an important role in a variety of diseases,but its effect on innate antiviral immunity has not been reported.This paper mainly discusses the fine regulation of IFN-1 generation and its own signal by MID1.Methods(1)Cells were transfected with overexpressed MIDI plasmids or knockdown MID1 plasmids,and then infected with VSV or SeV or H1N1 virus.The effect of overexpressed or knockdown MID1 on virus replication was analyzed by Quantitative Realtime PCR or Western Blot.(2)The effect of MIDI on IFN? mRNA was detected by Realtime qPCR,and the effect of MID1 on IFN? switched Lucifersae activity was detected by double luciferase reporter gene technology,and the effect node of MIDI on IFN-I signaling was screened,to investigate the regulation of MID1 on the node ubiquitin level and protein level.(3)IRF3-deficient mutants were constructed,transfected cells with these mutants,and the binding regions of MID1 and IRF3 were studied by immunoprecipitation and Western Blot.The specific sites of MID1 regulating IRF3 ubiquitination were further analyzed.(4)Realtime qPCR or Western Blot was used to study the effect of MID1 on the antiviral efficiency of IFN-I,and the correlation between MID1 and the level of STAT1,a key protein in IFN-I signals.(5)MID1-targeted protein was identified by Realtime qPCR or Western Blot,and the effect of MID1 on the protein level and ubiquitination level was studied by immunoprecipitation and Western Blot.Results:(1)Overexpression of MID1 can up-regulate VSV,SeV and H1N1 virus RNA levels,while knockdown of MID1 can significantly inhibit the replication of these viruses.(2)MID1 inhibited IFN-I promoter activity,significantly down-regulated IFN-I mRNA level,and interacted with IRF3 to promote IRF3 degradation by upregulation of IRF3 ubiquitination level.(3)MID1 interacts on the I AD domain of IRF3,increasing its ubiquitination through the lysine site of IRF3 313 and promoting IRF3 degradation.(4)MID1 inhibits the phosphorylation and activation of the key signaling protein STAT1 and the expression of the interferon-stimulated gene ISGs,thereby inhibiting the IFN-I signaling pathway and antiviral efficiency.(5)MID1 negatively regulates IFN-I receptor IFNAR2 by ubiquitination,increasing the ubiquitination level of IFNAR2 and promoting the degradation of IFNAR2 by lysosome.Conclusion MID1 significantly reduced the production of IFN-I in the body and significantly reduced the antiviral efficiency of IFN-I.This study reveals for the first time the important role of MID1 in antiviral immunity,and may provide a new target and strategy for clinical antiviral therapy.