ABSTRACT
The membrane-associated RING-CH (MARCH) family of proteins are members of the E3 ubiquitin ligase family and are essential for a variety of biological functions. Currently, MARCH proteins are discovered to execute antiviral functions by directly triggering viral protein degradation or blocking the furin cleavage of viral class I fusion proteins. Here, we report a novel antiviral mechanism of MARCH1 and MARCH2 (MARCH1/2) in the replication of Pseudorabies virus (PRV), a member of the Herpesviridae family. We discovered MARCH1/2 restrict PRV replication at the cell-to-cell fusion step. Furthermore, MARCH1/2 block gB cleavage, and this is dependent on their E3 ligase activity. Interestingly, the blocking of gB cleavage by MARCH1/2 does not contribute to their antiviral activity in vitro. We discovered that MARCH1/2 are associated with the cell-to-cell fusion complex of gB, gD, gH, and gL and trap these viral proteins in the trans-Golgi network (TGN) rather than degrading them. Overall, we conclude that MARCH1/2 inhibit PRV by trapping the viral cell-to-cell fusion complex in TGN.
Subject(s)
Herpesvirus 1, Suid , Ubiquitin-Protein Ligases , Virus Replication , trans-Golgi Network , Herpesvirus 1, Suid/physiology , Animals , trans-Golgi Network/virology , trans-Golgi Network/metabolism , Ubiquitin-Protein Ligases/metabolism , Cell Fusion , Swine , Cell Line , Humans , Viral Proteins/metabolism , Viral Proteins/genetics , HEK293 Cells , Pseudorabies/virologyABSTRACT
The membrane-associated RING-CH 8 protein (MARCH8), a member of the E3 ubiquitin ligase family, has broad-spectrum antiviral activity. However, some viruses hijack MARCH8 to promote virus replication, highlighting its dual role in the viral lifecycle. Most studies on MARCH8 have focused on RNA viruses, leaving its role in DNA viruses largely unexplored. Pseudorabies virus (PRV) is a large DNA virus that poses a potential threat to humans. In this study, we found that MARCH8 inhibited PRV replication at the cell-to-cell fusion stage. Interestingly, our findings proved that MARCH8 blocks gB cleavage by recruiting furin but this activity does not inhibit viral infection in vitro. Furthermore, we confirmed that MARCH8 inhibits cell-to-cell fusion independent of its E3 ubiquitin ligase activity but dependent on the interaction with the cell-to-cell fusion complex (gB, gD, gH, and gL). Finally, we discovered that the distribution of the cell-to-cell fusion complex is significantly altered and trapped within the trans-Golgi network. Overall, our results indicate that human MARCH8 acts as a potent antiviral host factor against PRV via trapping the cell-to-cell fusion complex in the trans-Golgi network.
ABSTRACT
OBJECTIVE: To investigate the molecular-epidemiologic characteristics and genotypes of human calicivirus (HuCVs) in acute diarrhea patients in Hangzhou from 2009 to 2010. METHODS: Epidemiologic data and fecal specimens were collected from patients with acute diarrhea. HuCVs of 920 specimens were detected by PCR. PCR products of several positive samples were randomly selected and sequenced. All the sequences were analyzed, phylogenetically. RESULTS: 201 HuCVs positive cases were identified from 920 facal specimens (21.8%). 25 isolates would include norovirus GI-type, GII-type for 170 strains and sapovirus for 11 strains. Norovirus GI-type and GII-type were detected in four specimens at the same time. Other specimens were mixed infection with norovirus GII-type and sapovirus. Genotypes of HuCVs showed that norovirus GI subtypes were GI-1 (3 strains) and GI-2 (1 strain). Norovirus GII subtypes were GII-4/2006b variant strains (7 strains), GII-2 (1 strain), GII-7 (1 strain) and GII-4/2008 variant strains (2 strains); Sapovirus subtypes were GI-2 (5 strains), GI-1 (4 strains) and GII-1 (1 strain). The prevalence rates of HuCVs were different in seasons and age groups. CONCLUSION: HuCVs were one of the major pathogens causing acute diarrhea. Both multiple viruses and genotypes of HuCVs were found in the specimens. GII-4/2006b variant and similar strains were identified, probably as the prevalent strains from 2009 to 2010 in Hangzhou, Zhejiang province.
