Viruses are the best cellular biologists; with little genetic information they take control of the infected cell to self-perpetuate and spread worldwide. Understanding how they hijack the cell is complicated by the multifunctional nature of viral components and the large number of cellular factors they interact with. Alphaviruses such as Chikungunya virus have been studied for decades resulting in a plethora of information on host interactors, enzymatic and structural data on single domains or partial complexes. However, these findings provide fragmented snapshots of biological events, disconnected from the reality of infection, where complexes form dynamically over time and in distinct viral organelles. My team has shown how only four non-structural proteins form distinct viral macromolecular complexes carrying out replication in membrane organelles and trapping host factors in cytoplasmic alphagranules. We have now reconstituted in vitro bona fide full replication complexes, as found in the cell, allowing the realistic characterization of replication and host interaction mechanisms. CHIKO aims to provide a precise understanding of the sequence of events in chikungunya virus replication and cell hijacking, from the atomic to the cellular scale, using a broad range of microscopy, biophysicaland biochemical techniques to address three challenging questions:
Q1: Replication Complex: How do early, medium and late full replication complexes act individually and evolve?
Q2: Networking. How do full and partial complexes network with the host factors to hijack the cell and replicate?
Q3: In the cell. How similar are the in vitro reconstituted complexes to those found in the infected cell? In what cellular and organellecontext do they act and when?
The expected outcome is an unprecedented description of viral infection, fundamental for the conception of next generation antivirals, and revealing viral mechanisms with potential applications to RNA based therapies.
