HIV-1 replication requires the integration of the viral genome into the cell genome. A viral-encoded enzyme, integrase (IN), performs this critical step of infection and is a promising target for anti-viral therapeutics. If the catalytic properties of INs are well characterized, the mechanisms responsible for their site selectivity are still under investigation. Several cellular proteins, such as the LEDFGF/p75 transcription regulator, the RNA polymerase II machinery, nuclear pore proteins and specific modified histones have been proposed to be involved in IN selectivity at a genomic level. In addition, structural parameters of the target DNA helix (curvature, flexibility and topology) are proposed to regulate IN selectivity at a local level. Our team is studying the role and molecular mechanisms associated with these various parameters (Botbol et al., 2008; Lesbats et al., 2011; Morchikh et al., 2013; Benleulmi et al., 2015; Naughtin et al.,). This project aims to define the role of cellular DNA topology during HIV-1 integration. We will first compare already mapped integration sites and superhelicity profiles and search for possible correlations between these two parameters. We will then modify topoisomerases activity in infected cells and study the consequences on viral replication and integration. Finally, we will study in vitro, the direct effects on integration of two parameters of DNA topology, the twist and writhe of the DNA helix. This project relies on complementary in vivo, in vitro and in silico approaches. Bio-informatics tools are crucial for the correlative and statistical analyses of integration sites and superhelicity maps.

HIV-1 replication requires the integration of the viral genome into the cell genome. A viral-encoded enzyme, integrase (IN), performs this critical step of infection and is a promising target for anti-viral therapeutics. If the catalytic properties of INs are well characterized, the mechanisms responsible for their site selectivity are still under investigation. Several cellular proteins, such as the LEDFGF/p75 transcription co-activator, the RNA polymerase II machinery, nuclear pore proteins and specific modified histones have been proposed to be involved in IN selectivity at a genomic level but the underlying molecular mechanisms remain to be demonstrated. In addition, structural parameters of the target DNA helix (curvature, flexibility, topology) are proposed to regulate IN selectivity at a local level. Our aims are to study the role of these different parameters of IN selectivity, using both in vitro and in vivo approaches. In vitro, we will map integration sites on various target DNA substrates (naked DNA or chromatin, minicircles, plasmids with different topologies, transcribed templates) and will test the effect of purified proteins suspected to regulate IN selectivity. In vivo, integration sites will be mapped in cells depleted of these suspected regulators or in cells incubated with drugs targeting enzymes involved in transcription, DNA topology or histone modifications. Integration sites will be mapped using published or “home-made” protocols and the sites will be compared with DNA structural parameters, nucleosome positions, histone modifications or transcriptional parameters (published maps). Bio-informatics tools are crucial for these correlative and statistical analyses of integration sites. Our project relies on complementary in vivo, in vitro and in silico approaches. It should establish molecular and mechanistic rules of HIV-1 integration selectivity that could serve in the development of new antiviral strategies and of safer gene therapy vectors.

L'extraction des protéines humaines qui interagir avec des protéines virales par le séquençage des barcodes associés avec les protéines humaines et virales. Analyses structurales des protéines virales et humain pour trouver les sites d’accrochage.

Background: PLA2 is known to regulate vesicle secretion in diverse eukaryotic cells. We are interested in determining the putative role of PLA2 in secretion of apical vesicular organelles called micronemes and rhoptries in P. falciparum merozoites. PLA2 inhibitors such as 4-BPB are known to block growth of the related Apicomplexan parasite Toxoplasma gondii. There are 3 annotated PLA2 genes in the P. falciparum genome database (Pf3D70209100, PF3D71358000, PF3D70924000). We would like to analyze these putative PLA2 genes using bioinformatics to support our drug development studies.    

A new version of the iPPI-DB, a manually curated database that contains the structure, some physicochemical characteristics, the pharmacological data and the profile of the PPI targets of several hundred modulators of protein-protein interactions.

This new version will include:

- A maintenance application that facilitates and automates the updates of the database. The computation of the various physico-chemical properties of the modulators and chemical similarity screening on the Galaxy server of the Institut Pasteur.

- A new target-centric mode, based on the mapping of all druggable cavities at the core of PPI interfaces throughout the Protein Data Bank.

The ARIA (Ambiguous Restraints for Iterative Assignment) software, developed at the Structural Bioinformatics Unit, automatizes the treatment of NMR data and protein structure calculation by molecular dynamics simulation. To enhance the visibility of the software, it is necessary to develop a new web interface where users will be able to easily manage their data, perform calculations and analyze the results of the ARIA calculations.

The adenylate cyclase (CyaA) produced by B. pertussis, the causative agent of whooping cough, is one of the major virulence factors of this organism. CyaA plays an important role in the early stages of respiratory tract colonization by B. pertussis. This toxin uses an original intoxication mechanism: secreted by the virulent bacteria, it is able to invade eukaryotic target cells through a unique but poorly understood mechanism that involves a direct translocation of the catalytic domain across the plasma membrane. CyaA is a 1706-residue long protein organized in a modular fashion. The ATP-cyclizing, calmodulin-activated, catalytic domain (ACD) is located in the 400 amino-terminal residues. Once secreted by the bacteria, the toxin binds calcium in the extracellular milieu and refolds into a functional state. Then, CyaA translocates its catalytic domain directly across the plasma membrane from the extracellular medium to the host cell cytoplasm where, upon activation by endogenous calmodulin, it increases the concentration of cAMP to supraphysiological levels that ultimately leads to the cell death. Recently, we succeeded to refold CyaA in a stable and monomeric form that is fully folded and functional (at variance with all prior procedures in which the polypeptides were largely aggregated upon urea removal). Both calcium and molecular confinement are mandatory to produce the monomeric state and CyaA acylation also strongly contributes to the refolding process. We further show that the monomeric preparation displayed hemolytic and cytotoxic activities suggesting that the monomer is the genuine, physiologically active form of the toxin. Hence, despite recent advances in the understanding of CyaA, its mechanisms of cell intoxication process, in particular the membrane translocation step, remains poorly understood from a fundamental perspective. The description of the molecular events occurring prior to and during the translocation of the catalytic domain across the lipi