RESUMO
The viral nuclear egress complex (NEC) allows herpesvirus capsids to escape from the nucleus without compromising the nuclear envelope integrity. The NEC lattice assembles on the inner nuclear membrane and mediates the budding of nascent nucleocapsids into the perinuclear space and their subsequent release into the cytosol. Its essential role makes it a potent antiviral target, necessitating structural information in the context of a cellular infection. Here we determined structures of NEC-capsid interfaces in situ using electron cryo-tomography, showing a substantial structural heterogeneity. In addition, while the capsid is associated with budding initiation, it is not required for curvature formation. By determining the NEC structure in several conformations, we show that curvature arises from an asymmetric assembly of disordered and hexagonally ordered lattice domains independent of pUL25 or other viral capsid vertex components. Our results advance our understanding of the mechanism of nuclear egress in the context of a living cell.
Assuntos
Capsídeo , Núcleo Celular , Microscopia Crioeletrônica , Membrana Nuclear , Liberação de Vírus , Núcleo Celular/metabolismo , Núcleo Celular/virologia , Humanos , Membrana Nuclear/metabolismo , Capsídeo/metabolismo , Proteínas do Capsídeo/metabolismo , Proteínas do Capsídeo/genética , Nucleocapsídeo/metabolismo , Tomografia com Microscopia Eletrônica , Proteínas Virais/metabolismo , Proteínas Virais/genética , Herpesviridae/fisiologia , Herpesviridae/genéticaRESUMO
Individual functional viral morphogenesis events are often dynamic, short, and infrequent and might be obscured by other pathways and dead-end products. Volumetric live cell imaging has become an essential tool for studying viral morphogenesis events. It allows following entire dynamic processes while providing functional evidence that the imaged process is involved in viral production. Moreover, it allows to capture many individual events and allows quantitative analysis. Finally, the correlation of volumetric live-cell data with volumetric electron microscopy (EM) can provide crucial insights into the ultrastructure and mechanisms of viral morphogenesis events. Here, we provide an overview and discussion of suitable imaging methods for volumetric correlative imaging of viral morphogenesis and frame them in a historical summary of their development.