Genetic Characteristics Of Porcine Trims And The Mechanism Of TRIM21 Affecting PCV2 Infection

Tripartite motif(TRIM)gene family is a group of middle-sized subfamilies that mainly act on post-translational modification.It has RING,B-box and coiled coil domains(RBCC domains)at N-terminal.TRIMs have many functions,such as participating in immune response,cell stress response and influencing virus replication.Studies have shown that TRIM protein can directly regulate different steps in the virus life cycle,or induce the production of antiviral cytokines through innate immune receptor-mediated signal transduction pathway.Porcine circovirus type 2(PCV2)is a small,non enveloped,single stranded circular DNA virus.PCV2 can inhibit or even damage the host’s immune system,and can co-infect with other porcine viruses,leading to a variety of diseases.The virus is transmitted horizontally by mouth,nose,secretion and excreta,and vertically by placenta or semen.However,there is no relevant research on porcine TRIMs involved in PCV2 regulation.It is reported in the literature that Tripartite motif-containing protein 21(TRIM21)of human and murine origin has a broad-spectrum antiviral effect,and porcine TRIM21 may have an inhibitory effect on the infection of porcine viruses PRRSV and PEDV.In this study,drawing a phylogenetic tree of 61 porcine TRIM genes(p TRIMs)found that porcine TRIM21 is more closely related to porcine TRIM5,TRIM6,TRIM34 and TRIM38,among which TRIM6,TRIM21 and TRIM38 have RBCC-PRY /SPRY domain,suggesting that porcine TRIM6,TRIM21 and TRIM38 may have similar antiviral activity and can be used as a targeted choice for antiviral genes.PCV2 was used to infect PK-15 cells and screened by RNA-seq analysis.It was found that there were significant differences in the expression of 10 types of p TRIMs.The detection of m RNA expression level showed that TRIM21 was significantly expressed in PCV2-infected PK-15 cells.Therefore,TRIM21 is the main research object in the follow-up of this research.PCV2 was used to infect TRIM21 overexpression and knockout cell lines,and it was found that TRIM21 overexpression could promote the proliferation of PCV2,but the knockout of TRIM21 produced the opposite result.Furthermore,methods such as immunoblotting,fluorescent quantitative PCR,and ELISA proved that TRIM21 promotes the expression of IFNβ and IFNγ and pro-inflammatory factors IL-6 and TNFα after PCV2 infection.Myeloid cell nuclear differentiation antigen-like protein(MNDAL)is a member of the IFI200 family.Preliminary research in our laboratory found that MNDAL may be involved in cell apoptosis induced by PCV2 infection.This study found that after PCV2 infects PK-15 cells,TRIM21 may promote the expression of MNDAL and BCL-2,inhibit the production of P53,thereby inhibiting the apoptosis induced by PCV2 infection,and ultimately promote the proliferation of PCV2.Additionally,co-immunoprecipitation and laser confocal analysis found that TRIM21 interacts with the Rep protein of PCV2,and it is mainly distributed around the nucleus.In conclusion,this study confirmed that TRIM21 could promote PCV2 infection,which could provide new targets and ideas for the future research of anti porcine virus.