Venezuelan Equine Encephalitis Virus Capsid Protein Forms a Tetrameric Complex with CRM1 and Importin α/β That Obstructs Nuclear Pore Complex Function

Abstract

Development of the cellular antiviral response requires nuclear translocation of multiple transcription factors and activation of a wide variety of cellular genes. To counteract the antiviral response, several viruses have developed an efficient means of inhibiting nucleocytoplasmic traffic. In this study, we demonstrate that the pathogenic strain of Venezuelan equine encephalitis virus (VEEV) has developed a unique mechanism of nuclear import inhibition. Its capsid protein forms a tetrameric complex with the nuclear export receptor CRM1 and the nuclear import receptor importin ␣/␤. This unusual complex accumulates in the center channel of the nuclear pores and blocks nuclear import mediated by different karyopherins. The inhibitory function of VEEV capsid protein is determined by a short 39-amino-acid-long peptide that contains both nuclear import and supraphysiological nuclear export signals. Mutations in these signals or in the linker peptide attenuate or completely abolish capsid-specific inhibition of nuclear traffic. The less pathogenic VEEV strains contain a wide variety of mutations in this peptide that affect its inhibitory function in nuclear import. Thus, these mutations appear to be the determinants of this attenuated phenotype. This novel mechanism of inhibiting nuclear transport also shows that the nuclear pore complex is vulnerable to unusual cargo receptor complexes and sheds light on the importance of finely adjusted karyopherin-nucleoporin interactions for efficient cargo translocation.

The Amino-Terminal Domain of Alphavirus Capsid Protein Is Dispensable for Viral Particle Assembly but Regulates RNA Encapsidation through Cooperative Functions of Its Subdomains

“…In the case of SINV, helix I was shown to be responsible for dimerization of capsid molecules, required for virus assembly (17). In the case of VEEV, it was demonstrated to function as a nuclear export signal (NES) playing a critical role in inhibition of nuclear pore trafficking (36,37). In a recent study, we also showed that in VEEV capsid, SD2 was capable of accumulating adaptive mutations (35).…”

“…8B and C), which could result in higher infectious titers. The identified mutation was in an interesting position, in the capsid-specific NLS (36,37). SD2 has a common function in the alphaviruses in assembly of NC, but in VEEV it also functions as an NES (36,37), required for blocking the nuclear pores.…”

“…The identified mutation was in an interesting position, in the capsid-specific NLS (36,37). SD2 has a common function in the alphaviruses in assembly of NC, but in VEEV it also functions as an NES (36,37), required for blocking the nuclear pores. Therefore, as we have demonstrated in our previous extensive studies (43,44), deletion of NES likely led to a higher level of VEEV capsid accumulation in the nuclei and thus made it incapable of forming NC.…”

HIV-1 remodels the nuclear pore complex

“…For instance, NPC destabilization may result from the association of Nups and integrated proviral cDNA or nuclear vRNA during transcription (Capelson et al, 2010;Hou and Corces, 2010;Strambio-De-Castillia et al, 2010). HIV-1 may disrupt NPCs to evade antiviral responses, as seen in other viruses (Gustin and Sarnow, 2002;Fontoura et al, 2005;Bardina et al, 2009;Porter and Palmenberg, 2009;Atasheva et al, 2010;Ren et al, 2010). Another possibility is that encapsidated Nup62 may be required for efficient delivery of the PIC into the nuclei of newly infected cells (Fig.…”

The role of type I interferon in the immunobiology of chikungunya virus

“…Alphaviruses also induce widespread host translational and transcriptional shut down in favour viral protein synthesis (Aguilar, Weaver et al 2007. The capsid protein of the encephalitic VEEV and EEEV has been found to form a complex that inhibits host gene transcription by blocking the trafficking of cellular proteins through the nuclear membrane (Garmashova, Atasheva et al 2007, Atasheva, Fish et al 2010. SFV and SINV have been found to inhibit host transcription via nsp2, which translocates to the nucleus and acts to degrade RNA polymerase II (Akhrymuk, Kulemzin et al 2012).…”