Grass carp reovirus capsid protein interacts with cellular proteasome subunit beta-type 7: Evidence for the involvement of host proteasome during aquareovirus infection.

The eukaryotic proteasome is a large multi-subunit complex that plays an important role in a wide range of fundamental cellular functions by degrading un-needed or damaged proteins, which also can be inverted or manipulated by viruses to favor viral infection. In this study, we demonstrated that proteasome subunit beta-type 7 (PSMB7), a proteasome-constitutive protein that is important for proteasome assembly, interacts with grass carp reovirus (GCRV) capsid proteins. Yeast 2-hybrid assay indicates that capsid protein VP38 of genotype Ⅲ GCRV could bind PSMB7, and this mutual interaction was further confirmed by pull-down, co-immunoprecipitation and subcellular co-localization assays. Furthermore, VP38 homologous proteins, VP7 from genotype I and VP35 from genotype II GCRV, can also interact with host PSMB7 in similar protein-protein interaction assays. Finally, PSMB7 expression level remains stable during GCRV infection, while, psmb7 gene transcription was repressed upon GCRV challenge; interaction with PSMB7 doesn't result in protein degradation of either VP7 or VP38 during viral infection. Thus, the interaction between host PSMB7 and viral capsid protein might suggest that interfering with PSMB7-mediated proteasome assembly should be involved in efficient aquareovirus infection.