HIV-1 Integrase Assembles Multiple Species of Stable Synaptic Complex Intasomes That Are Active for Concerted DNA...

Area of Science:

• Molecular Biology
• Structural Biology
• Virology

Background:

• Retroviral DNA integration is orchestrated by intasomes, nucleoprotein complexes where viral DNA ends are bridged by integrase (IN) multimers.
• High-resolution studies of HIV-1 intasomes often utilize IN fused with an Sso7d domain, which reduces aggregation and facilitates structural analysis.
• Previous structural data revealed diverse intasome architectures (tetrameric, dodecameric) for HIV-1, contrasting with the unique multimeric assemblies of related retroviruses.

Purpose of the Study:

• To investigate whether the Sso7d fusion domain contributes to the observed heterogeneity in HIV-1 intasome assembly.
• To determine if wild-type HIV-1 integrase exhibits similar multimeric assembly properties as the Sso7d-fused variant.

Main Methods:

• Biochemical and structural analyses were performed on intasomes assembled with wild-type HIV-1 integrase.
• Negative stain and cryo-electron microscopy (cryo-EM) were employed to characterize the intasome structures and multimeric states.

Main Results:

• Wild-type HIV-1 IN assembled a similar range of multimeric intasome species as observed with Sso7d-IN.
• Both wild-type and Sso7d-IN intasomes displayed the same common core architecture.
• Intasome stacks, arising from domain swapping, were observed in both wild-type and Sso7d-IN complexes.
• The propensity for multimeric assembly is an intrinsic characteristic of HIV-1 IN, not dependent on the Sso7d domain.

Conclusions:

• The Sso7d domain does not confer the heterogeneity observed in HIV-1 intasome assembly.
• The assembly of diverse multimeric intasome species is an intrinsic property of wild-type HIV-1 integrase.
• A common intasome core architecture can be assembled in various ways across different retroviral species, enabling catalysis.