Novel Role for Protein Inhibitor of Activated STAT 4 (PIAS4) in the Restriction of Herpes Simplex Virus 1 by the Cellular Intrinsic Antiviral Immune Response.
Bottom Line: Despite characterization of the host factors that rely on SUMOylation to exert their antiviral effects, the enzymes that mediate these SUMOylation events remain to be defined.Moreover, in the absence of ICP0, high-molecular-weight SUMO-conjugated proteins do not accumulate if HSV-1 DNA does not replicate.The protein inhibitor of activated STAT (PIAS) family of SUMO ligases is predominantly associated with the suppression of innate immune signaling.
Affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.Show MeSH
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Mentions: The SIM-mediated colocalization of PIAS4 with PML was predominant, although not necessary for PIAS4 localization within replication compartments. The direct or indirect association of PIAS4 with PML could therefore conceal relevant interactions mediated by the other domains of PIAS4 that contribute to replication compartment localization. To address this possibility, the localization of wild-type and mutant eYFP.PIAS4 proteins was evaluated during wild-type HSV-1 infection, when ICP0 efficiently mediates PML degradation (70, 71). As for ICP0- mutant HSV-1 infection, eYFP did not accumulate in wild-type HSV-1 replication compartments, whereas eYFP.PIAS4 did (Fig. 7A and B). The accumulation of eYFP.PIAS4 within wild-type HSV-1 replication compartments confirms that this localization is not disrupted by ICP0 and occurs independently of PML. EYFP-PIAS4 was distributed throughout wild-type HSV-1 replication compartments, similar to the distribution of endogenous PIAS4 (Fig. 7J). This distribution differed from that of eYFP.PIAS4 in ICP0- mutant HSV-1 replication compartments, where it localized to subdomains within individual replication compartments (compare Fig. 6J and 7J). These data suggest that although fusion with eYFP does not adversely affect PIAS4 accumulation in replication compartments, it may stabilize the SIM-mediated association of PIAS4 with PML. SIM-dependent interactions, however, were not essential for PIAS4 localization in ICP0- or wild-type HSV-1 replication compartments (Fig. 6G and 7G). Furthermore, it should be noted that eYFP fusion in itself did not promote association with PML (Fig. 5B).
Affiliation: MRC-University of Glasgow Centre for Virus Research (CVR), Glasgow, Scotland, United Kingdom.