The HIV-1 Pre-Integration Complexes: Structures, Functions and Dynamics

After retroviral infection of a target cell, during the early phase of replication, the HIV-1 genomic viral RNA is reverse transcribed by the viral reverse transcriptase to generate the double-stranded viral DNA that interact with viral and cellular proteins to form the pre-integration complex (PIC). Viral integrase (IN) is a key component of the PIC and is involved in several steps of replication notably in reverse transcription, nuclear import, chromatin targeting and integration. Viral components such as IN cannot perform these functions on their own and need to recruit host cell proteins to efficiently carry out the different processes. IN is a flexible protein, property allowing its interaction with multiple partners and enabling its multiple functions in viral replication. The molecular mechanisms and dynamics of these processes remain largely unknown. Purification of proteins that participate in these large transient complexes is impeded by low amounts, heterogeneity, instability and poor solubility. To circumvent these difficulties we develop methodologies that enable the production of stable complexes for structural and functional studies [1] as well as system for the production of multi-protein complexes from mammalian cells enabling assembly of entire complexes within cells. Using these strategies we reconstruct in vitro stable and soluble complexes around IN. We use cryo-EM combined with X-ray crystallography to solve structures of the IN/LEDGF/DNA [2] and IN/LEDGF/INI1/DNA [3] complexes. Other IN complexes involved in the PIC nuclear translocation and integration as well as IN post-translational modifications (phosphorylation and acetylation) have been characterized and are under study.[1] Levy et al. (2016) Nature comm. 7: 10932[2] Michel et al. (2009) EMBO J., 28, 980-991[3] Maillot et al. (2013) PLoS ONE 8(4): e60734