Dataset Information

Dynamic competition for hexon binding between core protein VII and lytic protein VI promotes adenovirus maturation and entry.

ABSTRACT: Adenovirus minor coat protein VI contains a membrane-disrupting peptide that is inactive when VI is bound to hexon trimers. Protein VI must be released during entry to ensure endosome escape. Hexon:VI stoichiometry has been uncertain, and only fragments of VI have been identified in the virion structure. Recent findings suggest an unexpected relationship between VI and the major core protein, VII. According to the high-resolution structure of the mature virion, VI and VII may compete for the same binding site in hexon; and noninfectious human adenovirus type 5 particles assembled in the absence of VII (Ad5-VII-) are deficient in proteolytic maturation of protein VI and endosome escape. Here we show that Ad5-VII- particles are trapped in the endosome because they fail to increase VI exposure during entry. This failure was not due to increased particle stability, because capsid disruption happened at lower thermal or mechanical stress in Ad5-VII- compared to wild-type (Ad5-wt) particles. Cryoelectron microscopy difference maps indicated that VII can occupy the same binding pocket as VI in all hexon monomers, strongly arguing for binding competition. In the Ad5-VII- map, density corresponding to the immature amino-terminal region of VI indicates that in the absence of VII the lytic peptide is trapped inside the hexon cavity, and clarifies the hexon:VI stoichiometry conundrum. We propose a model where dynamic competition between proteins VI and VII for hexon binding facilitates the complete maturation of VI, and is responsible for releasing the lytic protein from the hexon cavity during entry and stepwise uncoating.

SUBMITTER: Hernando-Perez M

PROVIDER: S-EPMC7306765 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Dynamic competition for hexon binding between core protein VII and lytic protein VI promotes adenovirus maturation and entry.

Hernando-Pérez Mercedes M Martín-González Natalia N Pérez-Illana Marta M Suomalainen Maarit M Condezo Gabriela N GN Ostapchuk Philomena P Gallardo José J Menéndez Margarita M Menéndez Margarita M Greber Urs F UF Hearing Patrick P de Pablo Pedro J PJ San Martín Carmen C

Proceedings of the National Academy of Sciences of the United States of America 20200528 24

Adenovirus minor coat protein VI contains a membrane-disrupting peptide that is inactive when VI is bound to hexon trimers. Protein VI must be released during entry to ensure endosome escape. Hexon:VI stoichiometry has been uncertain, and only fragments of VI have been identified in the virion structure. Recent findings suggest an unexpected relationship between VI and the major core protein, VII. According to the high-resolution structure of the mature virion, VI and VII may compete for the sam ...[more]

PMID: 32467158

Similar Datasets

Project description:Recent evidence has revealed that the reorganization of nuclear domains is largely mediated by liquid-liquid phase separation (LLPS). During viral infection, numerous nuclear domains undergo significant changes through LLPS for and against the replication of the virus. However, the regulatory mechanism of LLPS in response to viral infection and its detailed functions in viral replication remain unclear. In this study, we found that the activity of the nucleolar protein NPM1, a remodeling factor for the chromatin-like structure of adenovirus DNA, to induce LLPS is required for deposition of adenovirus core protein VII in a subnuclear domain, the virus-induced post-replication (ViPR) body, in the late phases of infection. The interaction between NPM1 and protein VII was responsible for initiating LLPS. The inhibition of LLPS by 1,6-hexanediol treatment resulted in the dispersion of protein VII from the ViPR bodies. These findings suggest that protein VII accumulates in the ViPR bodies in concert with the LLPS formation of NPM1 triggered by protein VII. After photobleaching of EGFP-NPM1 in the ViPR bodies, EGFP-NPM1 showed a relatively fast recovery half-time, indicating the fluid-like properties of NPM1 in this compartment. Importantly, NPM1 depletion decreased the genome packaging in the viral capsids, possibly owing to the formation of a defective adenovirus core. This study highlights the dynamic interplay between viral pathogens and the host nucleus for the reorganization of membrane-less compartments that facilitate their replication.ImportanceIn this study, we explored how adenoviruses utilize a process known as liquid-liquid phase separation (LLPS) to enhance their replication. We focused on a cellular chromatin remodeling protein, NPM1, which plays a crucial role in nucleolar formation through LLPS. NPM1 facilitates LLPS by interacting with adenovirus protein VII, effectively accumulating protein VII into membrane-less compartments called virus-induced post-replication bodies. NPM1 functions as a molecular chaperone of protein VII to assemble viral chromatin by transferring protein VII to viral DNA. Remarkably, when NPM1 was depleted, this process was disrupted, decreasing viral genome packaging. These findings shed light on a critical aspect of virus-host interactions, illustrating how adenovirus utilizes NPM1-mediated LLPS activity. Our findings provide valuable insights into the dynamic interplay between viruses and the host nucleus.

Project description: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.

Dataset Information

Dynamic competition for hexon binding between core protein VII and lytic protein VI promotes adenovirus maturation and entry.

Publications

Dynamic competition for hexon binding between core protein VII and lytic protein VI promotes adenovirus maturation and entry.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets