The NUCleoproteic ARCHitecture of HIV (NUCARCHIV)
There is still a lot to understand about the molecular mechanisms that drive the HIV life cycle, especially from the production of viral particle in an infected cell to the targeting of its genome towards the nucleus of a new target cell. Knowledge-driven research is here an important task to achieve with inestimable basic and applied perspectives about HIV-1 as a paradigm for system biology and molecular medicine and for the design of new therapeutical, prophylactic and diagnostical strategies in the fight against AIDS and related disease.
The "NUCleoproteic ARChitecture of HIV" (NUCARCHIV) group is developing a research project at the frontier between Virology, Cellular & Molecular Biology, Biochemistry, Structural Biology and Nanosciences in order to decipher the internal architecture of HIV. With the development of Nanosciences using atomic force microscopy (AFM) and photonic devices for single particule analysis, studying the HIV self-assembly process and its architectural remodeling is becoming a fruitful approach to understand, to detail and to control the internal mechanisms driven by the viral machine to shape the viral infectious state.
Our main objectives are to address experimental tasks in order to better understand how this machine works to achieve its spatiotemporal program from assembly in the producing cell to nuclear entry in the target cell, with actually a special attention to the budding/maturation steps. Additionnaly, our studies are leading to design new pharmacological approaches to affect the infectious process by reducing the viral production or by producing inactive particles. To develop these tasks, we have also engaged an intense and pluridisciplinary networking activity in order to share our projects with complementary and enthusiastic partners both locally and worldwide.
Our original experimental approaches are based on in vitro reconstitutions. Until now, we were only using purified components focusing on a convenient combination of Biochemistry, Molecular biology and Biophysics with a special care dedicated to nucleic acids. Since recently, we are also using cellular strategies to produce virus-like particles. One important goal in our experimental devices is to analyse our samples by hi-resolution microscopies and to lead to illustrated models that can focus on macromolecular architectures, their internal interactomes and the way these architectures are formed, transformed and deformed.
This project has been started in IDIBAPS, AIDS Research Group in March 2008 thanks to Jose Maria Gatell in an unexpected, but fruitful clinical environment, thanks to Robert Gorelick and Jeffrey Lifson, our supporters during the obscure time, thanks to the University UPMC Paris 6 to allow the long-term delocalisation of one of its molecular biologist as a researcher at IDIBAPS and thanks to the external financial support from the european FP7-framework Marie Curie and Health programs as well as from the french ANRS. Our team is presently member of the THINPAD consortium granted after the call FP7-HEALTH-2013-INNOVATION-2 for “targeting the HIV-1 Nucleocapsid Protein to fight Antiretroviral Drug Resistance “ up to August 2016.
State of the art / general view:
In the HIV internal architecture, a protein coat, the capsid (CA), internalizes the viral genomic RNA within a ribonucleoproteic complex named nucleocapsid (NC), whereas the matrix protein (MA) outside of the capsid connects the viral particle with a cholesterol-rich lipid envelope containing a limited subset of anchored envelope protein (Env). This molecular architecture is formed during the viral self-assembly process by the MA, CA, NC precursor, the Gag polyprotein, that selectively recruits both the viral dimer RNA and the GagPol polyprecursor of the three viral enzymes: protease (PR), reverse transcriptase (RT) and integrase (IN). Then, its maturation is catalyzed by the viral protease (PR), subsequently to its self-processing from GagPol and leading to its transformation between the viral release from the producing cell and the conversion of its genome from RNA to DNA within the target cell, according to a spatiotemporal program that is still poorly understood.
Anti-PR drugs (PIs) are acting in such a context generating non-infectious particles. Recently, the last generation of anti-IN drugs (ALLINIs) has also been shown to generate such particles, thus highlighting the critical importance for HIV-1 to respect its spatiotemporal program generating from within its core infectious properties. Some anti-RT drugs issued from a subclass of NNRTIs are also shown to strongly affect this program by directly reducing the viral production. Limiting the availability of critical lipids like cholesterol seems also to limit the viral production. Other targets located in this internal architecture, especially the most predominently Gag polyprotein, are therefore available for antiviral development, especially the NC domain of Gag with its two highly conserved zinc fingers and its critical position between PR and RT actions.
The NC domain of Gag is required for selective RNA capture and cooperativity factor leading to accurate assembly as well as for recruting the cellular ESCRT machinery in charge of viral budding in partnership with the viral RNA and the C-terminal Gag flanking domain (p6). It appeared also as a target of cellular factors that restrict viral infection. Gag NC is processed by PR in the nascent particle by a three-steps mechanism into the mature NCp7 which acts as a RNA-condensing and RNA-chaperone absolutely required for RT and for proper DNA routing to the nuclear chromatin. Both processing and plan of action of NC, in between PR-directed assembly and RT-directed disassembly, are also implicated in controlling sequestration or release of other proteins within the HIV core, for example the viral protein R (Vpr) and p6 respectively.
The impressive plasticity of the Gag/GagPol assembly/budding/maturation, as well as the remodeling and trafficking of mature capsid within the target cell, both requiring highly complex virus–host confrontations under characterization, are now focusing the attention of many labs as original, but paradigmatic features of HIV and relatives, with strong implications in Biology, Medicine, Pharmacology and Technosciences.