Nuclear export of cutaneous HPV8 E7 oncoprotein is mediated by a leucine-rich nuclear export signal via a CRM1 pathway

Viral Subversion of the Chromosome Region Maintenance 1 Export Pathway and Its Consequences for the Cell Host

In eukaryotic cells, the spatial distribution between cytoplasm and nucleus is essential for cell homeostasis. This dynamic distribution is selectively regulated by the nuclear pore complex (NPC), which allows the passive or energy-dependent transport of proteins between these two compartments. Viruses possess many strategies to hijack nucleocytoplasmic shuttling for the benefit of their viral replication. Here, we review how viruses interfere with the karyopherin CRM1 that controls the nuclear export of protein cargoes. We analyze the fact that the viral hijacking of CRM1 provokes are-localization of numerous cellular factors in a suitable place for specific steps of viral replication. While CRM1 emerges as a critical partner for viruses, it also takes part in antiviral and inflammatory response regulation. This review also addresses how CRM1 hijacking affects it and the benefits of CRM1 inhibitors as antiviral treatments.

Identification of nuclear localization signal and nuclear export signal of VP1 from the chicken anemia virus and effects on VP2 shuttling in cells

BACKGROUND

VP1 of the chicken anemia virus (CAV) is a structural protein that is required for virus encapsulation. VP1 proteins are present both in the nucleus and cytoplasm; however, the functional nuclear localization signal (NLS) and nuclear export signal (NES) of VP1 are still unknown. This study aimed to characterize the NLS and NES motifs of VP1 using bioinformatics methods and multiple-site fragment deletions, and investigate shuttling of VP2 from nucleus to cytoplasm by co-transfection with VP1.

METHODS

Two putative NLS motifs were predicted by the WoLF PSORT and NLStradamus programs from the amino acid sequence of VP1. Three NES motifs of VP1 were predicted by the NetNES 1.1 Server and ELM server programs. All mutants were created by multiple-site fragment deletion mutagenesis. VP1 and VP2 were co-expressed in cells using plasmid transfection.

RESULTS

A functional NLS motif was identified at amino acid residues 3 to 10 (RRARRPRG) of VP1. Critical amino acids 3 to 10 were significantly involved in nuclear import in cells and were evaluated using systematic deletion mutagenesis. Three NES motifs of VP1 were predicted by the NetNES 1.1 Server and ELM server programs. A functional NES was identified at amino acid residues 375 to 388 (ELDTNFFTLYVAQ). Leptomycin B (LMB) treatment demonstrated that VP1 export from nucleus to cytoplasm occurred through a chromosome region maintenance 1 (CRM1)-dependent pathway. With co-expression of VP1 and VP2 in cells, we observed that VP1 may transport VP2 from nucleus to cytoplasm.

CONCLUSION

Our data showed that VP1 of CAV contained functional NLS and NES motifs that modulated nuclear import and export through a CRM1-dependent pathway. Further, VP1 may play a role in the transport of VP2 from nucleus to cytoplasm.