No abstract

To better understand how positive-strand (+) RNA viruses assemble membrane-associated replication complexes (RCs) to synthesize, process, and transport viral RNA in virus-infected cells, we determined both the high-resolution structure of the core RNA replicase of chikungunya virus and the native RC architecture in its cellular context at subnanometer resolution, using in vitro reconstitution and in situ electron cryotomography, respectively. Within the core RNA replicase, the viral polymerase nsP4, which is in complex with nsP2 helicase-protease, sits in the central pore of the membrane-anchored nsP1 RNA-capping ring. The addition of a large cytoplasmic ring next to the C terminus of nsP1 forms the holo-RNA-RC as observed at the neck of spherules formed in virus-infected cells. These results represent a major conceptual advance in elucidating the molecular mechanisms of RNA virus replication and the principles underlying the molecular architecture of RCs, likely to be shared with many pathogenic (+) RNA viruses.

No abstract

All positive-strand (+) RNA viruses assemble membrane-associated replication complexes (RCs) for viral RNA synthesis in virus-infected cells. However, how these multi-component RCs assemble and function in synthesizing, processing, and transporting viral RNAs to the cytosol remains poorly defined. Here, we determined both the structure of the core RNA replicase of chikungunya virus (family Togaviridae) at a near-atomic level and the native RC architecture in its cellular context at the subnanometer resolution, using in vitro reconstitution and in situ electron cryotomography, respectively. Within the core RNA replicase (nsP1+2+4), the viral RNA-dependent RNA polymerase nsP4, in complex with nsP2 helicase-protease, was found to co-fold with the membrane-anchored nsP1 RNA-capping dodecameric ring and is located asymmetrically within nsP1 central pore. This complex forms the minimal core RNA replicase, while the addition of a large cytoplasmic ring next to the C-terminus of nsP1 forms the holo-RNA-RC as observed at the neck of spherules formed in virus-infected cells. These results represent a major conceptual advance in elucidating the molecular mechanisms of RNA virus replication and the principles underlying the molecular architecture of RCs, likely to be shared with many pathogenic (+) RNA viruses. At last, our study will direct the needed development of antiviral therapies targeting RCs of pathogenic viruses.

No abstract