Mechanism Research Of Nuclear Factor I/A(NFIA)and NFIB Inhibit Porcine Reproductive And Respiratory Syndrome Virus(PRRSV)Replication

Porcine reproductive and respiratory syndrome(PRRS)is a highly contagious disease that seriously harmed the world's pig farming industry.As the pathogen,PRRSV has been in existence for more than 30 years since its appearance,and there is still no effective response.PRRSV will escape and destroy host's immune system,result in a persistent infection and immunosuppression.That makes the prevention and cure to be extremely difficult.Therefore,we need to study in depth continue,and further expound the molecular mechanism of the body against PRRSV.So that we can provide theoretical basis and direction for the development of new drugs or vaccines.Nuclear factor I(NFI)protein could broadly bind to specific sequences of cellular or viral genes and regulate multiple gene's duplication and transcription as a sitespecific DNA-binding protein.Interferon(IFN)is a cytokine which produced by monocytes and lymphocytes and it regulates various functions such as immunity,antiviral,and antitumor.PRRSV can inhibit the host's natural immunity and stop the production of type I interferon(IFN-I).Recently,studies show that Nuclear factor I/A(NFIA)and NFIB can improve the expression of IFN-I and inhibit PRRSV replication,but the molecular mechanism of that was not clear yet.Therefore,this article explored the molecular mechanism of NFIA and NFIB inhibit PRRSV replication with MARC-145 cells as the cellular infection model.Firstly,we overexpressed and inhibited NFIA and NFIB in MARC145 cells,confirmed that NFIA and NFIB can inhibit PRRSV replication.Secondly,we resolved the functional domains of NFIA and NFIB by truncation analysis,and found that the N-terminal domain of NFIA and NFIB is the key to resist PRRSV.Finally,we performed functional site mutations on the N-terminal domain of NFIA and NFIB,and found that NFIA and NFIB no longer inhibit PRRSV replication after the mutation of DNA binding functional site.Furthermore,we also determined the activity of IFN-? promoter by luciferase reporter assay about the truncation and mutation of NFIA and NFIB,and found that domain deletion or functional site mutation neither increase the IFN-? promoter activity.This study deep analyzed the functional domains and core functional sites of NFIA and NFIB,preliminary expounded the molecular mechanism of NFIA and NFIB inhibit PRRSV replication,and provided an important reference for further research about the natural immunity against PRRSV.