Abstract
Adenovirus (AdV) morphogenesis is a complex process, many aspects of which remain unclear. In particular, it is not settled where in the nucleus assembly and packaging occur, and whether these processes occur in a sequential or a concerted manner. Here we use immunofluorescence and immunoelectron microscopy (immunoEM) to trace packaging factors and structural proteins at late times post infection by either wildtype virus or a delayed packaging mutant. We show that representatives of all assembly factors are present in the previously recognized peripheral replicative zone, which therefore is the AdV assembly factory. Assembly intermediates and abortive products observed in this region favor a concurrent assembly and packaging model comprising two pathways, one for capsid proteins and another one for core components. Only when both pathways are coupled by correct interaction between packaging proteins and the genome is the viral particle produced. Decoupling generates accumulation of empty capsids and unpackaged cores.
Highlights
AdV virions consist of a 95 nm, icosahedral pseudoT = 25 protein shell enclosing a non-icosahedral DNA-protein core
Virus genomes are packaged inside capsids by one of two mechanisms: concerted, where a protein shell is built around the genome, or sequential, where the genome is pumped into a preformed empty shell
Adenoviruses have been studied for more than 60 years, these two basic aspects of their biology had not been elucidated. We address these two questions by determining the location in the cell nucleus where adenovirus assembly and packaging factors meet, describing failed assembly products containing unpackaged genomes, and showing for the first time images of adenovirus capsid fragments in the process of engulfing the viral DNA
Summary
Each capsid facet has 12 trimers of the major coat protein, hexon. The core contains the terminal protein (TP) and the maturation protease (AVP) [1,2,3]. AdV assembly occurs in the nucleus, where hexon and penton, together with the minor coat proteins and the packaging protein L1 52/55 kDa, assemble into empty capsids. Viral genomes and core proteins are inserted into these capsids to yield noninfectious, immature particles [4]. These contain the precursor version of several capsid (pIIIa, pVI, pVIII) and core (pVII, pμ, pTP) proteins, as well as L1 52/55 kDa. Mature virions are produced upon cleavage of these precursors by AVP [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
