Nucleolar-cytoplasmic shuttling of PRRSV nucleocapsid protein: a simple case of molecular mimicry or the complex regulation by nuclear import, nucleolar localization and nuclear export signal sequences.
The order Nidovirales, which includes the arteriviruses and coronaviruses, incorporate a cytoplasmic replication scheme; however, the nucleocapsid (N) protein of several members of this group localizes to the nucleolus suggesting that viral proteins influence nuclear processes during replication. The relatively small, 123 amino acid, N protein of porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus, presents an ideal model system for investigating the properties and mechanism of N protein nucleolar localization. The PRRSV N protein is found in both cytoplasmic and nucleolar compartments during infection and after transfection of gene constructs that express N-enhanced green fluorescent protein (EGFP) fusion proteins. Experiments using oligopeptides, truncated polypeptides and amino acid-substituted proteins have identified several domains within PRRSV N protein that participate in nucleo-cytoplasmic shuttling, including a cryptic nuclear localization signal (NLS) called NLS-1, a functional NLS (NLS-2), a nucleolar localization sequence (NoLS), as well as a possible nuclear export signal (NES). The purpose of this paper is to review our current understanding of PRRSV N protein shuttling and propose a shuttling scheme regulated by RNA binding and post-translational modification.
Rowland
Raymond R R
RR
Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, KS 66506, USA. browland@vet.ksu.edu
Yoo
Dongwan
D
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D018716:Molecular Mimicry; D019590:Nucleocapsid Proteins / Q000378:metabolism*; D019316:Porcine respiratory and reproductive syndrome virus / Q000378:metabolism*; D021382:Protein Sorting Signals
D019590:Nucleocapsid Proteins; D021382:Protein Sorting Signals