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Putative reaction intermediates in Crm1-mediated nuclear protein export.
1Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10021, USA.
The Journal of Biological Chemistry
|May 29, 1999
Summary
We uncovered new protein interactions in the nuclear export of HIV-1 Rev protein. This research details how Rev, Crm1, and RanGTP interact with nucleoporins and RanBP1 to regulate nuclear export.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- The human immunodeficiency virus type 1 (HIV-1) protein Rev is crucial for viral replication, mediating the nuclear export of unspliced viral RNAs.
- Crm1 (chromosome region maintenance 1) is a key nuclear export receptor involved in the transport of Rev and other proteins containing a nuclear export signal (NES).
- Understanding the intricate protein interactions governing Rev-mediated nuclear export is vital for developing antiviral strategies.
Purpose of the Study:
- To elucidate novel interactions and mechanisms involved in Crm1-mediated nuclear export of the HIV-1 Rev protein.
- To characterize the role of nucleoporins, RanGTP, RanBP1, RanGAP, and RanGEF in the Rev export pathway.
- To propose a comprehensive model for Crm1-mediated nuclear export based on newly discovered molecular events.
Main Methods:
- In vitro biochemical assays were employed to study protein-protein interactions.
- Complex formation and disassembly were analyzed using purified proteins including Rev, Crm1, RanGTP, nucleoporins, RanBP1, RanGAP, and RanGEF.
- The role of GTP hydrolysis and nucleotide exchange factors in regulating these interactions was investigated.
Main Results:
- A Rev/Crm1/RanGTP complex interacts with specific nucleoporins (Nup42, Nup159) but not others, leading to Rev release.
- RanBP1 displaces nucleoporins to form a RanBP1/RanGTP/Crm1 complex, which is disassembled by RanGAP-mediated GTP hydrolysis.
- Surprisingly, the RanBP1/RanGTP/Crm1 complex can also be disassembled by RanGEF independently of GTP hydrolysis.
- Crm1 and Rev stimulate the recycling of a Ran/RanGEF complex, facilitating the reformation of the Rev/Crm1/RanGTP export complex.
Conclusions:
- A detailed model for Crm1-mediated nuclear export of HIV-1 Rev is proposed, highlighting novel interactions and regulatory steps.
- The findings reveal a complex interplay between the export receptor (Crm1), the cargo (Rev), the GTPase (Ran), and accessory factors (nucleoporins, RanBP1, RanGAP, RanGEF).
- This study provides new insights into the molecular mechanisms of nuclear export, with potential implications for understanding viral pathogenesis and developing therapeutic interventions.