CryoEM analysis of capsid assembly and structural changes upon interactions with a host restriction factor, TRIM5α

Area of Science:

• Virology
• Structural Biology
• Molecular Biology

Background:

• HIV-1 infection involves viral core uncoating after cell entry.
• TRIM5α is a host restriction factor that inhibits HIV-1 by inducing premature uncoating.
• The precise mechanism of TRIM5α interaction with the HIV-1 capsid is not fully understood.

Purpose of the Study:

• To elucidate the structural mechanism by which TRIM5α interacts with and disrupts the HIV-1 capsid.
• To investigate the effect of TRIM5α binding on HIV-1 capsid assembly and stability.

Main Methods:

• Utilized cryo-electron microscopy (cryoEM) to visualize structural changes in HIV-1 capsid (CA) upon TRIM5α binding.
• Combined cryoEM with pair-wise cysteine mutations for crosslinking to map TRIM5α interaction sites on CA.
• Analyzed in vitro CA assemblies and purified intact HIV-1 cores.

Main Results:

• Demonstrated that TRIM5α directly binds to the HIV-1 capsid via its CC-SPRY domains.
• Showed that TRIM5α binding leads to disruption and fragmentation of the capsid's surface lattice.
• Identified that disruption occurs specifically at the inter-hexamer interfaces of the capsid.

Conclusions:

• Direct TRIM5α binding destabilizes the HIV-1 capsid structure, leading to premature uncoating.
• The findings provide a molecular mechanism for TRIM5α-mediated restriction of HIV-1.
• The described methodology can be applied to study other multi-protein complex interactions.