Jab1 Mediates Cytoplasmic Localization and Degradation of West Nile Virus Capsid Protein

Abstract

The clinical manifestations of West Nile virus (WNV), a member of the Flavivirus family, include febrile illness, sporadic encephalitis, and paralysis. The capsid (Cp) of WNV is thought to participate in these processes by inducing apoptosis through mitochondrial dysfunction and activation of caspase-9 and caspase-3. To further identify the molecular mechanism of the WNV capsid protein (WNVCp), yeast two-hybrid assays were employed using WNV-Cp as bait. Jab1, the fifth subunit of the COP9 signalosome, was subsequently identified as a molecule that interacts with WNVCp. Immunoprecipitation and glutathione S-transferase pulldown assays confirmed that direct interaction could occur between WNVCp and Jab1. Immunofluorescence microscopy demonstrated that the overexpressed WNVCp, which localized to the nucleolus, was translocated to the cytoplasm upon its co-expression with Jab1. When treated with leptomycin B, Jab1-facilitated nuclear exclusion of WNVCp was prevented, which indicated that the CRM1 complex is required for Jab1-facilitated nuclear export of WNVCp. Moreover, Jab1 promoted the degradation of WNVCp in a proteasome-dependent way. Consistent with this, WNVCpmediated cell cycle arrest at the G 2 phase in H1299 was prevented by exogenous Jab1. Finally, an analysis of WNVCp deletion mutants indicated that the first 15 amino acids were required for interaction with Jab1. Furthermore, the double-point mutant of the WNVCp, P5A/P8A, was incapable of binding to Jab1. These results indicate that Jab1 has a potential protective effect against pathogenic WNVCp and might provide a novel target site for the treatment of disease caused by WNV.

Uncoupling cis -Acting RNA Elements from Coding Sequences Revealed a Requirement of the N-Terminal Region of Dengue Virus Capsid Protein in Virus Particle Formation

“…A growing number of host proteins that interact with flavivirus C proteins have been reported (4,5,18,28). For instance, by use of twohybrid systems, several cellular proteins that interact with WNV C have been identified (29,42). Less is known about possible interactions between DENV C and cellular proteins, but it is likely that C interacts with different host factors in infected mosquito and human cells.…”

Multiple regions in dengue virus capsid protein contribute to nuclear localization during virus infection

“…This feature appears to be conserved among flaviviruses, as other investigators have detected C proteins of Kunjin virus, West Nile virus and Japanese encephalitis virus (JEV) in both the cytoplasm and nuclei of infected mammalian cells (Westaway et al, 1997;Mori et al, 2005;Oh et al, 2006). Three stretches of Arg/Lys-rich sequence in the dengue virus C protein have been proposed to serve as nuclear-localization signals (NLSs): KKAR, located at aa 6-9; KKSK, located at aa 73-76; and the bipartite sequence RKEIGRMLNILNRRRR, located at aa 85-100 (Bulich & Aaskov, 1992).…”

“…Kinetics of C protein localization to nuclei and nucleoli of dengue virus-infected cells Several investigators have reported different patterns of dengue virus and other flavivirus C protein nuclear localization, or lack thereof, in many cell lines, which may reflect cellular differences and methodological variations (Tadano et al, 1989;Bulich & Aaskov, 1992;Westaway et al, 1997;Ng et al, 2001;Wang et al, 2002;Mori et al, 2005;Oh et al, 2006). To affirm the phenomenon in this study, subcellular localization of dengue virus C protein was assessed during infection of two mammalian cell lines (PS and Vero) and a mosquito cell line (C6/36) with a dengue serotype 2 virus, strain 16681, by using indirect IFA.…”

Geminiviruses Subvert Ubiquitination by Altering CSN-Mediated Derubylation of SCF E3 Ligase Complexes and Inhibit Jasmonate Signaling inArabidopsis thaliana

“…Although interactions with components of the CRLs have been described previously for DNA and RNA viruses, only few examples of interactions with the CSN complex have been reported, all limited to animal viruses (Mahalingam et al, 1998;Oh et al, 2006;Tanaka et al, 2006;Hsieh et al, 2007). Even though, as for C2-CSN5, those interactions seem to play a role during virus infection (Oh et al, 2006;Tanaka et al, 2006;Hsieh et al, 2007), the mechanisms proposed point to a redirection of proteosomal degradation rather than to an effect on the derubylating activity of the CSN complex itself.…”

“…Even though, as for C2-CSN5, those interactions seem to play a role during virus infection (Oh et al, 2006;Tanaka et al, 2006;Hsieh et al, 2007), the mechanisms proposed point to a redirection of proteosomal degradation rather than to an effect on the derubylating activity of the CSN complex itself.…”