biostudies-literatureUnknown27(15)Haas GReplication of Cauliflower mosaic virus (CaMV), a plant double-stranded DNA virus, requires the viral translational transactivator protein P6. Although P6 is known to form cytoplasmic inclusion bodies (viroplasms) so far considered essential for virus biology, a fraction of the protein is also present in the nucleus. Here, we report that monomeric P6 is imported into the nucleus through two importin-alpha-dependent nuclear localization signals, and show that this process is mandatory for CaMV infectivity and is independent of translational transactivation and viroplasm formation. One nuclear function of P6 is to suppress RNA silencing, a gene regulation mechanism with antiviral roles, commonly counteracted by dedicated viral suppressor proteins (viral silencing suppressors; VSRs). TransgenThe EMBO journal2102-12https://www.ebi.ac.uk/biostudies/studies/S-EPMC2516879biostudies-literatureNuclear import of CaMV P6 is required for infection and suppression of the RNA silencing factor DRB4.PMC2516879Himber CHaas GFukuhara TGeldreich AMoissiard GBureau MKeller MVoinnet OAzevedo JfalseNuclear import of CaMV P6 is required for infection and suppression of the RNA silencing factor DRB4.Replication of Cauliflower mosaic virus (CaMV), a plant double-stranded DNA virus, requires the viral translational transactivator protein P6. Although P6 is known to form cytoplasmic inclusion bodies (viroplasms) so far considered essential for virus biology, a fraction of the protein is also present in the nucleus. Here, we report that monomeric P6 is imported into the nucleus through two importin-alpha-dependent nuclear localization signals, and show that this process is mandatory for CaMV infectivity and is independent of translational transactivation and viroplasm formation. One nuclear function of P6 is to suppress RNA silencing, a gene regulation mechanism with antiviral roles, commonly counteracted by dedicated viral suppressor proteins (viral silencing suppressors; VSRs). Transgen2008-01-01T00:00:00Z2008 Aug2025-04-19T07:38:11.129Z2019-03-27T00:16:12ZS-EPMC25168791861509810.1038/emboj.2008.129