Year: 2017
Type: article
Abstract: ABSTRACT Human adenoviruses (Ad) are double-stranded DNA (dsDNA) viruses associated with infectious diseases, but they are better known as tools for gene delivery and oncolytic anticancer therapy. Atomic structures of Ad provide the basis for the development of antivirals and for engineering efforts toward more effective applications. Since 2010, atomic models of human Ad5 have been derived independently from photographic film cryo-electron microscopy (cryo-EM) and X-ray crystallography studies, but discrepancies exist concerning the assignment of cement proteins IIIa, VIII, and IX. To clarify these discrepancies, we employed the technology of direct electron counting to obtain a cryo-EM structure of human Ad5 at 3.2-Å resolution. Our improved structure unambiguously confirms our previous cryo-EM models of proteins IIIa, VIII, and IX and explains the likely cause of conflict in the crystallography models. The improved structure also allows the identification of three new components in the cavity of hexon—the cleaved N terminus of precursor protein VI (pVIn), the cleaved N terminus of precursor protein VII (pVIIn2), and mature protein VI. The binding of pVIIn2—and, by extension, that of genome-condensing pVII—to hexons is consistent with the previously proposed dsDNA genome-capsid coassembly for adenoviruses, which resembles that of single-stranded RNA (ssRNA) viruses but differs from the well-established mechanism of pumping dsDNA into a preformed protein capsid exemplified by tailed bacteriophages and herpesviruses. IMPORTANCE Adenovirus is a double-edged sword to humans: it is a widespread pathogen but can be used as a bioengineering tool for anticancer and gene therapies. The atomic structure of the virus provides the basis for antiviral and application developments, but conflicting atomic models for the important cement proteins IIIa, VIII, and IX from conventional/film cryo-EM and X-ray crystallography studies have caused confusion. Using cutting-edge cryo-EM technology with electron counting, we improved the structure of human adenovirus type 5 and confirmed our previous models of cement proteins IIIa, VIII, and IX, thus clarifying the inconsistent structures. The improved structure also reveals atomic details of membrane-lytic protein VI and genome-condensing protein VII and supports the previously proposed genome-capsid coassembly mechanism for adenoviruses.
Source: Journal of Virology
DOI: 10.1128/jvi.00850-17
Authors: Xinghong Dai, Lily Wu, Ren Sun, Z. Hong Zhou
Language: English
Subfield: Structural Biology
Domain: Life Sciences
Open Access status: bronze
Funders: National Science Foundation, National Institutes of Health, National Institute of General Medical Sciences, National Institute of Allergy and Infectious Diseases, National Institute of Dental and Craniofacial Research, National Center for Research Resources, National Center for Advancing Translational Sciences, Clinical and Translational Science Institute, University of California, Los Angeles
Awards: MRI: Acquisition of a direct electron detector for the UCLA Titan electron microscope, In situ atomic structures of the Kaposi's sarcoma-associated herpesvirus portal-terminase complex and glycoproteins, Direct Detection Device for atomic resolution cryoEM of macromolecular complexes, West/Midwest Consortium for High-Resolution Cryo Electron Microscopy, G562934659, High-End CryoEM Instrument for the UCLA Electron Imaging Center for Nanomachines, High-Resolution CryoEM Reconstruction of Large Complexes, Genome structure, transcription and packaging of dsRNA viruses, UCLA Clinical and Translational Science Institute
OpenAlex ID: W2762983419