Non-encapsidation activities of the capsid proteins of positive-strand RNA viruses

Abstract

Viral capsid proteins (CPs) are characterized by their role in forming protective shells around viral genomes. However, CPs have additional and important roles in the virus infection cycles and in the cellular response to infection. These activities involve CP binding to RNAs in both sequence-specific and nonspecific manners as well as association with other proteins. This review focuses on CPs of both plant and animal-infecting viruses with positive-strand RNA genomes. We summarize the structural features of CPs and describe their modulatory roles in viral translation, RNA-dependent RNA synthesis, and host defense responses.

Phosphorylation of the Brome Mosaic Virus Capsid Regulates the Timing of Viral Infection

“…Many other viruses have capsid proteins with positively charged and highly flexible sequences that translocate from within the virion to the external surface of the virion (7,53). It is possible that these sequences are acted on by host proteins to regulate the disassembly of the virions and enable viral gene expression and replication.…”

“…The BMV CP has multiple regulatory activities during infection (6,7). Each BMV capsid contains 180 subunits of the CP arranged in a Tϭ3 symmetry.…”

“…A CP subunit has structural features similar to those of a histone protein. Both have an intrinsically disordered N-terminal arm rich in positively charged residues followed by sequences that fold into a globular domain (7). The N-terminal arm contributes to the differential encapsidation of BMV RNA, has the ability to translocate from the internal cavity to the outside of the virion, and is preferentially cleaved during proteolysis (8,9).…”

<div>Phosphorylation of the viral coat protein regulates RNA virus infection</div>

“…In addition to forming a protective shell around the viral genome, it is increasingly appreciated to be involved in encapsidationindependent activities, including the regulation of viral RNA synthesis, viral translation, and the modulation of the host innate immune response. 23 Viruses typically encode one or two CPs with several common structural features ( Figure 1). 23,24 Many CPs have highly flexible N-or C-terminal tails that contain positively charged residues that can interact with RNA.…”

“…23 Viruses typically encode one or two CPs with several common structural features ( Figure 1). 23,24 Many CPs have highly flexible N-or C-terminal tails that contain positively charged residues that can interact with RNA. All viral CPs contain regions of higher order structure that form the shelllike domain around the encapsidated RNA in virions.…”