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Measurement of In Vitro Integration Activity of HIV-1 Preintegration Complexes
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A Tripartite Complex HIV-1 Tat-Cyclophilin A-Capsid Protein Enables Tat Encapsidation That Is Required for HIV-1
Malvina Schatz1, Laetitia Marty1, Camille Ounadjela1
1Institut de Recherche en Infectiologie de Montpellier, UMR 9004 CNRS, Université de Montpellier, Montpellier, France.
Journal of Virology
|May 2, 2023
Summary
We discovered a complex allowing HIV-1 Tat protein to enter virus particles. This encapsidated Tat is crucial for initiating viral gene transcription and boosting HIV infection early on.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- HIV-1 Tat protein is essential for viral gene expression, particularly transcription.
- The mechanism of Tat incorporation into HIV-1 virions has been unclear.
- Cyclophilin A (CypA) binds HIV-1 capsid protein (CA) and is packaged into virions.
Purpose of the Study:
- To investigate the mechanism of Tat encapsidation into HIV-1 virions.
- To characterize the role of encapsidated Tat in early viral infection stages.
Main Methods:
- Assembly and purification of a Tat-CypA-CA tripartite complex.
- Biochemical and biophysical interaction studies.
- Analysis of HIV infectivity and viral gene expression in Tat-depleted and Tat-reconstituted viruses.
Main Results:
- A Tat-CypA-CA complex facilitates Tat encapsidation into HIV virions.
- Viruses lacking encapsidated Tat showed significantly reduced infectivity (5-10 fold decrease).
- Absence of encapsidated Tat impaired reverse transcription (~50%) and transcription (>90%).
Conclusions:
- A Tat-CypA-CA complex enables Tat incorporation into HIV virions.
- Encapsidated Tat is essential for efficient initiation of viral transcription and production during early infection.
- This pre-packaged Tat boosts initial viral replication before newly synthesized Tat is available.
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