Ovarian Tumor Domain-Containing Viral Proteases Evade Ubiquitin- and ISG15-Dependent Innate Immune Responses

Abstract

Ubiquitin (Ub) and interferon-stimulated gene product 15 (ISG15) reversibly conjugate to proteins and mediate important innate antiviral responses. The ovarian tumor (OTU) domain represents a superfamily of predicted proteases found in eukaryotic, bacterial, and viral proteins, some of which have Ub-deconjugating activity. We show that the OTU domain-containing proteases from nairoviruses and arteriviruses, two unrelated groups of RNA viruses, hydrolyze Ub and ISG15 from cellular target proteins. This broad activity contrasts with the target specificity of known mammalian OTU domain-containing proteins. Expression of a viral OTU domain-containing protein antagonizes the antiviral effects of ISG15 and enhances susceptibility to Sindbis virus infection in vivo. We also show that viral OTU domain-containing proteases inhibit NF-kappaB-dependent signaling. Thus, the deconjugating activity of viral OTU proteases represents a unique viral strategy to inhibit Ub- and ISG15-dependent antiviral pathways.

The cysteine protease domain of porcine reproductive and respiratory syndrome virus non-structural protein 2 antagonizes interferon regulatory factor 3 activation

“…Interestingly, here we found that the PL2 cysteine protease domain of Nsp2 was responsible for IFN antagonism. This result is consistent with a previous report that PRRSV Nsp2 deconjugates ubiquitin and ISG15 from cellular target proteins (Frias-Staheli et al, 2007). Therefore, the PL2 domain of Nsp2 not only acts as a viral protease and deubiquitinating (DUB) enzyme, but can also inhibit the induction of type I IFN.…”

“…Nsp2 aa 47-240 (Tyr47-Cys240) and Nsp2 aa 47-323 (Tyr47-Leu323) are required to maintain the trans-and cis-cleavage activities, respectively (Han et al, 2009). The PL2 protease of PRRSV Nsp2 is thought to be a new member of the ovarian tumour (OTU) protease superfamily, capable of deconjugating ubiquitin and ISG15 (Frias-Staheli et al, 2007). The highly conserved amino acids among OTU members are located at the putative Cys55-His124 catalytic motif of Nsp2.…”

Mapping of the interaction domains of the Crimean–Congo hemorrhagic fever virus nucleocapsid protein

“…The full-length sequence encoding the N protein was cloned into pCAGGS for mammalian expression. The plasmids expressing the full-length L protein or the truncation mutants HA-L (1-1325), HA-L (1325HA-L ( -2590 and HA-L (2590-3945) have been described previously (Frias-Staheli et al, 2007). The mutant HA-L (1-1325) DZF was generated by site direct mutagenesis (Stratagene), according to the manufacturer's instructions, changing cysteine in positions 609 and 613 for alanine.…”

“…Therefore we attempted to characterize this interaction and determine which regions within the L protein mediate the N-L association. For this purpose, we utilized three plasmids expressing haemagglutinin (HA)-tagged L protein truncation mutants (Frias-Staheli et al, 2007) (Fig. 1a).…”

“…The large segment (L) encodes the L protein, a multifunctional 448 kDa protein containing a viral RNA-dependent RNA polymerase (RdRp) domain and an ovarian tumour (OTU) domain in the N-terminal region. The OTU domain has been shown to contain deubiquitinating and deISGylating activities, which were proven to be important for the evasion of the innate immune response and therefore could potentially be targeted for development of antiviral approaches (Frias-Staheli et al, 2007). The medium segment (M) encodes the envelope proteins Gc and Gn and the non-structural proteins GP38 and NSm (Bergeron et al, 2007;Erickson et al, 2007;Sanchez et al, 2002Sanchez et al, , 2006, and the small segment (S) encodes the nucleoprotein or nucleocapsid protein (N protein) as has now been nominated by the Ninth Report of the International Committee on Taxonomy of Viruses (Plyusnin et al, 2012).…”