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Nucleocytoplasmic shuttling by human immunodeficiency virus type 1 Vpr
M P Sherman1, C M de Noronha, M I Heusch
1Gladstone Institute of Virology and Immunology, University of California, San Francisco, California 94141-9100, USA.
Journal of Virology
|January 11, 2001
Summary
Human immunodeficiency virus type 1 (HIV-1) Vpr protein facilitates nuclear import in non-dividing cells. This study identifies Vpr as a nucleocytoplasmic shuttling protein, crucial for HIV-1 infection.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Human immunodeficiency virus type 1 (HIV-1) infects non-dividing cells like macrophages.
- Nuclear import of the viral preintegration complex is essential for HIV-1 replication.
- Vpr, matrix, and integrase proteins contain nuclear import signals.
Purpose of the Study:
- To investigate the nuclear import and export mechanisms of HIV-1 Vpr.
- To characterize the novel nuclear import signals within Vpr.
- To determine if Vpr functions as a nucleocytoplasmic shuttling protein.
Main Methods:
- Fusion protein constructs (GFP-PK-Vpr) were created and analyzed for cellular localization.
- Leptomycin B (LMB), a CRM1 inhibitor, was used to assess nuclear export.
- Modified heterokaryon analysis was employed to map Vpr's nuclear export signal.
Main Results:
- Vpr contains a bipartite nuclear localization signal (NLS) in its carboxy-terminal region.
- Vpr fusion proteins shuttle between the cytoplasm and nucleus, indicated by LMB treatment.
- Both leucine-rich alpha-helices of Vpr are necessary for nuclear import.
- The Vpr nuclear export signal (NES) overlaps with an NLS in the second leucine-rich helix.
Conclusions:
- HIV-1 Vpr is a nucleocytoplasmic shuttling protein.
- Vpr utilizes unique NLSs that bypass classical import pathways.
- Vpr's ability to shuttle is critical for HIV-1's nuclear import and infection of non-dividing cells.