Abstract
The HIV-1 nucleocapsid is formed during protease (PR)-directed viral maturation, and is transformed into pre-integration complexes following reverse transcription in the cytoplasm of the infected cell. Here, we report a detailed transmission electron microscopy analysis of the impact of HIV-1 PR and reverse transcriptase (RT) on nucleocapsid plasticity, using in vitro reconstitutions. After binding to nucleic acids, NCp15, a proteolytic intermediate of nucleocapsid protein (NC), was processed at its C-terminus by PR, yielding premature NC (NCp9) followed by mature NC (NCp7), through the consecutive removal of p6 and p1. This allowed NC co-aggregation with its single-stranded nucleic-acid substrate. Examination of these co-aggregates for the ability of RT to catalyse reverse transcription showed an effective synthesis of double-stranded DNA that, remarkably, escaped from the aggregates more efficiently with NCp7 than with NCp9. These data offer a compelling explanation for results from previous virological studies that focused on i) Gag processing leading to nucleocapsid condensation, and ii) the disappearance of NCp7 from the HIV-1 pre-integration complexes. We propose that HIV-1 PR and RT, by controlling the nucleocapsid architecture during the steps of condensation and dismantling, engage in a successive nucleoprotein-remodelling process that spatiotemporally coordinates the pre-integration steps of HIV-1. Finally we suggest that nucleoprotein remodelling mechanisms are common features developed by mobile genetic elements to ensure successful replication.
Highlights
The human immunodeficiency virus type I (HIV-1) encodes three enzymes: protease (PR), reverse transcriptase (RT) and integrase (IN)
NCp15 processing by PR requires single-stranded nucleic acids to generate NCp7, a reaction that results in nucleoprotein aggregation
In vitro processing of NCp15 (1 mM) by PR (Figure 1) was studied by examining the effect of several nucleic acids in order to address the positive effect on proteolysis, already shown for RNA [18,20]
Summary
The human immunodeficiency virus type I (HIV-1) encodes three enzymes: protease (PR), reverse transcriptase (RT) and integrase (IN). These facilitate the transfer of genetic information from the HIV-1 genome to the nuclear chromatin of the infected cell. Within the confines of the cytoplasm of the infected cell, the heterodimeric RT catalyses by a sophisticated process the conversion of the RNA genome into double-stranded DNA (see Animation S1, S2 for an animated and detailed model of reverse transcription). IN (presumably in a tetrameric form [4]) catalyses the concerted insertion of the two viral DNA ends into the cell’s chromosomal DNA, allowing the viral DNA or provirus to behave as a cellular genetic unit
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
