Lecture Pranav Shah

Pranav Shah

University of Oxford
Division of Structural Biology

From Chaos to Order: Characterization of Rotavirus Assembly Intermediates in Liquid-like Virus Factories

Host: Daniel Hurdiss

Rotavirus, a prototypic member of the multi-layered, double-stranded RNA-containing Reoviridae family, replicates in specialized cytoplasmic organelles called viroplasms—phase-separated condensates that serve as active sites for genome packaging and virion assembly. In this talk, I will present our comprehensive structural characterization of rotavirus assembly. Using cryo-electron tomography of infected cells, we elucidated the sequential, stepwise acquisition of capsid layers, identifying four key intermediates ranging from the pre-packaging single-layered particle to the fully assembled triple-layered virion. Our in situ approach revealed the recruitment of viral genomes by VP1 and a unique conformation of the VP4 spike during the transiently enveloped stage, providing atomic models for these critical steps in infectious particle formation.

Building on this, I will discuss our ongoing efforts to understand how viroplasm condensates coordinate assembly and genome packaging. Focusing on the key non-structural proteins NSP2 (an RNA chaperone) and NSP5 (an intrinsically disordered protein), we employ a multi-faceted structural approach. By integrating cryo-electron tomography (cryoET) and subtomogram averaging (STA), we directly compare and contrast condensates and viroplasms in infected cells, enabling us to map NSP2 interaction surfaces in a minimal well-defined system versus authentic viroplasms. This helps clarify the role viroplasms play in coordinating assembly and genome packaging.

Together, this work offers an unprecedented view into the intricate mechanisms of rotavirus assembly and provides novel insights into how viral biomolecular condensates tune protein dynamics and organization to facilitate complex replication processes.