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The HCPro from the Potyviridae family: an enviable multitasking Helper Component that every virus would like to have.

ABSTRACT: RNA viruses have very compact genomes and so provide a unique opportunity to study how evolution works to optimize the use of very limited genomic information. A widespread viral strategy to solve this issue concerning the coding space relies on the expression of proteins with multiple functions. Members of the family Potyviridae, the most abundant group of RNA viruses in plants, offer several attractive examples of viral factors which play roles in diverse infection-related pathways. The Helper Component Proteinase (HCPro) is an essential and well-characterized multitasking protein for which at least three independent functions have been described: (i) viral plant-to-plant transmission; (ii) polyprotein maturation; and (iii) RNA silencing suppression. Moreover, multitudes of host factors have been found to interact with HCPro. Intriguingly, most of these partners have not been ascribed to any of the HCPro roles during the infectious cycle, supporting the idea that this protein might play even more roles than those already established. In this comprehensive review, we attempt to summarize our current knowledge about HCPro and its already attributed and putative novel roles, and to discuss the similarities and differences regarding this factor in members of this important viral family.

SUBMITTER: Valli AA

PROVIDER: S-EPMC6638112 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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The HCPro from the Potyviridae family: an enviable multitasking Helper Component that every virus would like to have.

Valli Adrián A AA Gallo Araiz A Rodamilans Bernardo B López-Moya Juan José JJ García Juan Antonio JA

Molecular plant pathology 20170526 3

RNA viruses have very compact genomes and so provide a unique opportunity to study how evolution works to optimize the use of very limited genomic information. A widespread viral strategy to solve this issue concerning the coding space relies on the expression of proteins with multiple functions. Members of the family Potyviridae, the most abundant group of RNA viruses in plants, offer several attractive examples of viral factors which play roles in diverse infection-related pathways. The Helper ...[more]

PMID: 28371183

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Project description:Potyviridae is the largest family of plant-infecting RNA viruses and includes many agriculturally and economically important viral pathogens. The viruses in the family, known as potyvirids, possess single-stranded, positive-sense RNA genomes with polyprotein processing as a gene expression strategy. The N-terminal regions of potyvirid polyproteins vary greatly in sequence. Previously, we identified a novel virus species within the family, Areca palm necrotic spindle-spot virus (ANSSV), which was predicted to encode two cysteine proteases, HCPro1 and HCPro2, in tandem at the N-terminal region. Here, we present evidence showing self-cleavage activity of these two proteins and define their cis-cleavage sites. We demonstrate that HCPro2 is a viral suppressor of RNA silencing (VSR), and both the variable N-terminal and conserved C-terminal (protease domain) moieties have antisilencing activity. Intriguingly, the N-terminal region of HCPro1 also has RNA silencing suppression activity, which is, however, suppressed by its C-terminal protease domain, leading to the functional divergence of HCPro1 and HCPro2 in RNA silencing suppression. Moreover, the deletion of HCPro1 or HCPro2 in a newly created infectious clone abolishes viral infection, and the deletion mutants cannot be rescued by addition of corresponding counterparts of a potyvirus. Altogether, these data suggest that the two closely related leader proteases of ANSSV have evolved differential and essential functions to concertedly maintain viral viability.IMPORTANCE The Potyviridae represent the largest group of known plant RNA viruses and account for more than half of the viral crop damage worldwide. The leader proteases of viruses within the family vary greatly in size and arrangement and play key roles during the infection. Here, we experimentally demonstrate the presence of a distinct pattern of leader proteases, HCPro1 and HCPro2 in tandem, in a newly identified member within the family. Moreover, HCPro1 and HCPro2, which are closely related and typically characterized with a short size, have evolved contrasting RNA silencing suppression activity and seem to function in a coordinated manner to maintain viral infectivity. Altogether, the new knowledge fills a missing piece in the evolutionary relationship history of potyvirids and improves our understanding of the diversification of potyvirid genomes.

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The HCPro from the Potyviridae family: an enviable multitasking Helper Component that every virus would like to have.

Publications

The HCPro from the Potyviridae family: an enviable multitasking Helper Component that every virus would like to have.

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