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Cyclophilin A facilitates HIV-1 integration.

Adrian Padron1,2,3, Richa Dwivedi1,2, Rajasree Chakraborty1,2

  • 1Center for AIDS Health Disparities Research, Meharry Medical College, Nashville, Tennessee, USA.

Journal of Virology
|October 31, 2024
PubMed
Summary

Cyclophilin A (CypA) directly promotes HIV-1 integration, a crucial step in viral replication. This host factor binds the HIV-1 capsid, enhancing viral DNA integration within the host cell nucleus.

Keywords:
Cyclophilin A (CypA)capsidhuman immunodeficiency virus (HIV)integrationreverse transcription nuclear entry

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Area of Science:

  • Virology
  • Molecular Biology
  • Immunology

Background:

  • Cyclophilin A (CypA) is a host protein known to bind the HIV-1 capsid, aiding in reverse transcription and nuclear entry.
  • CypA also antagonizes TRIM5α, an antiviral factor restricting HIV-1 infection.
  • Recent findings suggest the HIV-1 capsid enters the nucleus intact before integration, highlighting potential nuclear roles for capsid-binding proteins.

Purpose of the Study:

  • To investigate whether the CypA-capsid interaction influences HIV-1 integration, a post-nuclear entry step.
  • To elucidate the mechanism by which CypA might regulate HIV-1 integration.
  • To determine if CypA's role in integration is independent of its known functions in reverse transcription, nuclear entry, and TRIM5α interaction.

Main Methods:

  • Compared HIV-1 integration levels in CypA-expressing (CypA+/+) versus CypA-depleted (CypA-/-) cells.
  • Utilized cyclosporin A (CsA) to inhibit CypA-capsid binding.
  • Tested HIV-1 capsid mutants (G89V, P90A) with impaired CypA binding.
  • Assessed the in vitro integration activity of HIV-1 preintegration complexes (PICs) from infected cells.
  • Examined the effect of CypA and TRIM5α depletion on PIC integration activity.

Main Results:

  • CypA depletion significantly reduced HIV-1 proviral DNA integration, independent of reverse transcription, nuclear entry, or TRIM5α presence.
  • Inhibition of CypA-capsid binding by CsA blocked integration in CypA+/+ cells but not CypA-/- cells.
  • HIV-1 capsid mutants deficient in CypA binding were impaired in integration in CypA+/+ cells.
  • PICs from CypA-/- cells exhibited lower in vitro integration activity compared to those from CypA+/+ cells.
  • CypA specifically stimulated PIC integration activity, an effect blocked by CsA.

Conclusions:

  • Cyclophilin A directly and positively regulates HIV-1 integration, a novel nuclear function.
  • The CypA-capsid interaction is critical for efficient viral DNA integration.
  • CypA's role in promoting HIV-1 integration is distinct from its effects on reverse transcription and TRIM5α antagonism.