Retroviral prototype foamy virus intasome binding to a nucleosome target does not determine integration efficiency

Area of Science:

• Molecular Biology
• Virology
• Structural Biology

Background:

• Retroviral integrase (IN) enzymes must integrate viral DNA into host chromatin.
• Prototype foamy virus (PFV) integrase forms a tetrameric intasome complex with viral DNA.
• The roles of outer subunit domains in PFV intasomes during nucleosome integration are unclear.

Purpose of the Study:

• To investigate the function of amino and carboxyl terminal domains (CTDs) of outer PFV intasome subunits during integration into nucleosomes.
• To determine how nucleosome binding correlates with integration efficiency and site selection.

Main Methods:

• Utilized the 601 nucleosome as a target substrate to assay PFV intasome integration activity and binding.
• Investigated the effects of outer protomer NED, NTD, and CTD domains on integration and binding.
• Assessed the impact of histone tails on intasome binding and integration.

Main Results:

• Outer protomer NED and NTD domains had no significant effect on integration efficiency, site selection, or binding.
• PFV intasome CTDs significantly altered nucleosome binding but had minimal impact on overall integration efficiency.
• Histone tails affected intasome binding but not integration efficiency or site selection.

Conclusions:

• Nucleosome binding does not directly correlate with PFV integration efficiency.
• Most intasome-nucleosome binding events appear to be unproductive for viral DNA integration.
• Outer subunit domains play differential roles in PFV intasome-nucleosome interactions.