Asymmetric reconstruction of mammalian reovirus reveals interactions among RNA, transcriptional factor \xb52 and capsid proteins

Muchen Pan,Z Hong Zhou,Chunhai Fan,Joon S Kang,Ana L Alvarez-Cabrera,Lihua Wang

doi:10.1038/s41467-021-24455-4

Abstract

Mammalian reovirus (MRV) is the prototypical member of genus Orthoreovirus of family Reoviridae. However, lacking high-resolution structures of its RNA polymerase cofactor μ2 and infectious particle, limits understanding of molecular interactions among proteins and RNA, and their contributions to virion assembly and RNA transcription. Here, we report the 3.3 Å-resolution asymmetric reconstruction of transcribing MRV and in situ atomic models of its capsid proteins, the asymmetrically attached RNA-dependent RNA polymerase (RdRp) λ3, and RdRp-bound nucleoside triphosphatase μ2 with a unique RNA-binding domain. We reveal molecular interactions among virion proteins and genomic and messenger RNA. Polymerase complexes in three Spinoreovirinae subfamily members are organized with different pseudo-D3d symmetries to engage their highly diversified genomes. The above interactions and those between symmetry-mismatched receptor-binding σ1 trimers and RNA-capping λ2 pentamers balance competing needs of capsid assembly, external protein removal, and allosteric triggering of endogenous RNA transcription, before, during and after infection, respectively.

Highlights

Mammalian reovirus (MRV) is the prototypical member of genus Orthoreovirus of family Reoviridae
MRV is the prototypical member of the Orthoreovirus genus of the Reoviridae[5], a large family of doublestranded RNA viruses, including the life-threatening human pathogen rotavirus[6]
MRV exhibits both similarities and differences in its genome and transcribing enzyme complex (TEC) organizations when compared to ARV and cytoplasmic polyhedrosis virus (CPV), two other members with known structures[22,24] of the Spinoreovirinae subfamily of the Reoviridae family

Summary

Introduction

Mammalian reovirus (MRV) is the prototypical member of genus Orthoreovirus of family Reoviridae. MRV is the prototypical member of the Orthoreovirus genus of the Reoviridae[5], a large family of doublestranded RNA (dsRNA) viruses, including the life-threatening human pathogen rotavirus[6] These viruses differ in two main aspects: the number of protein layers of their capsids and the presence (in the viruses of nine genera that comprise the Spinoreovirinae subfamily) or absence (in the viruses of six genera that comprise the Sedoreovirinae subfamily) of mRNA-capping turrets on the twelve icosahedral vertices of their innermost capsid layer[5]. Our results unveil the atomic structure of μ2 (which we show is an NTPase) and reveal interactions among RdRp λ3, λ1, μ2, and genomic and newly transcribed RNA, as well as among external capsid proteins, including the symmetrymismatched receptor-binding protein σ1 trimer and capping enzyme λ2 pentamer. As the high-resolution structures of MRV and of the Orthoreovirus genus of the Reoviridae, these structures fill in a critical knowledge gap in the ever-growing repertoire of dsRNA virus structures; several structural features provide mechanistic insights into allosteric triggering and catalytic regulation of endogenous RNA transcription inside multilayered members of the Spinoreovirinae subfamily of the Reoviridae

Methods

Results

Conclusion