Abstract
Picornaviruses are comprised of a positive-sense RNA genome surrounded by a protein shell (or capsid). They are ubiquitous in vertebrates and cause a wide range of important human and animal diseases. The genome encodes a single large polyprotein that is processed to structural (capsid) and non-structural proteins. The non-structural proteins have key functions within the viral replication complex. Some, such as 3Dpol (the RNA dependent RNA polymerase) have conserved functions and participate directly in replicating the viral genome, whereas others, such as 3A, have accessory roles. The 3A proteins are highly divergent across the Picornaviridae and have specific roles both within and outside of the replication complex, which differ between the different genera. These roles include subverting host proteins to generate replication organelles and inhibition of cellular functions (such as protein secretion) to influence virus replication efficiency and the host response to infection. In addition, 3A proteins are associated with the determination of host range. However, recent observations have challenged some of the roles assigned to 3A and suggest that other viral proteins may carry them out. In this review, we revisit the roles of 3A in the picornavirus life cycle. The 3AB precursor and mature 3A have distinct functions during viral replication and, therefore, we have also included discussion of some of the roles assigned to 3AB.
Highlights
Picornaviruses are comprised of a positive-sense RNA genome surrounded by a protein shell
This study reported that enterovirus A71 (EV-A71) 3A could bind to ATP1B3 in a Y-2-H assay and in coimmunoprecipitation experiments using epitope tagged proteins expressed in transfected cells
Could be readily co-purified along with strep-tagged AiV 3A in pull down experiments, whereas only ACBD3 was co-purified when the assay was carried out using strep-tagged 3A of several enteroviruses. These results suggested that the interaction between ACBD3 and PI4KB may be stabilized by AiV 3A, but not by enterovirus 3A
Summary
Picornaviruses are ubiquitous in nature and have been identified in all vertebrate classes [1] They are responsible for many diseases of medical importance, such as poliomyelitis (caused by poliovirus; PV), hand-foot-and mouth disease (caused by coxsackievirus (CV) A16; CVA9, and enterovirus A71; EV-A71) and the common cold (caused by human rhinoviruses; RV) [2]. The 3A proteins of picornaviruses are some of the most divergent across the different genera They have important roles in forming both the viral replication complex (RC). The different types of 2A proteins are indicated; 2Anpgp = 2A has an NPG/P motif; 2ANTPase = 2A with an NTP-binding motif; 2AH-box/NC = 2A with a H-box/NC motif; 2Apro = 2A has proteinase activity; 2A = 2A lacking a signature motif. Dicipiviruses are unusual and have two ORFs that are separated by an intergenic region (IGR) and have two IRES elements
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