The Second Open Reading Frame of the Avian Reovirus S1 Gene Encodes a Transcription-Dependent and CRM1-Independent Nucleocytoplasmic Shuttling Protein

Abstract

It was previously shown that the second open reading frame of the avian reovirus S1 gene encodes a 146-amino-acid nonstructural protein, designated p17, which has no known function and no sequence similarity to other known proteins. The results presented in this report demonstrate that p17 accumulates in the nucleoplasm of infected and transfected cells. An examination of the deduced amino acid sequence of p17 revealed the presence of a putative monopartite nuclear localization signal (NLS) between residues 119 and 128. Mutagenesis analysis revealed both that this sequence is indeed a functional NLS and that two of its basic residues are critical for the normal nuclear distribution of p17. An interspecies heterokaryon assay further showed that p17 shuttles continuously between the nucleus and the cytoplasm and that this activity is restricted to its NLS-containing C-terminal tail. Finally, an analysis of the intracellular distribution of p17 in the presence of inhibitors of both RNA polymerase II and CRM1 further revealed that the nucleocytoplasmic distribution of p17 is coupled to transcriptional activity and that the viral protein exits the nucleus via a CRM1-independent pathway.

Avian Reovirus Nonstructural Protein p17-Induced G 2 /M Cell Cycle Arrest and Host Cellular Protein Translation Shutoff Involve Activation of p53-Dependent Pathways

“…2B). This may suggest that the cell cycle perturbation effects may be unique to the p17 protein among the S-class proteins tested, which thus far has no structural similarity to another ARV protein (9).…”

“…The ARV genome encodes at least 10 structural proteins and four nonstructural proteins, but very little is known about the functions of most of these proteins. ARV p17 protein is a 146-aminoacid protein encoded by the S1 genome segment that contains three open reading frames which translate into p10, p17, and C (4,9,38,49,53,57). The p17 protein is a shuttle protein that continuously shuttles between the nucleus and the cytoplasm, making it available to participate in cellular nuclear processes such as gene transcription, DNA binding, and cell growth regulation (9,34).…”

The p17 Nonstructural Protein of Avian Reovirus Triggers Autophagy Enhancing Virus Replication via Activation of Phosphatase and Tensin Deleted on Chromosome 10 (PTEN) and AMP-activated Protein Kinase (AMPK), as well as dsRNA-dependent Protein Kinase (PKR)/eIF2α Signaling Pathways

“…Genome segment S1 possesses three open reading frames (ORF) that are translated into p10, p17, and C proteins, respectively. The p17 protein is a CRM1-independent nucleocytoplasmic shuttling protein that continuously shuttles between the nucleus and cytoplasm (1). It was proved that p17 plays an important role in regulating cell cycle and host cellular translation but does not induce cellular apoptosis (2)(3)(4).…”

Leaky Scanning and Scanning-independent Ribosome Migration on the Tricistronic S1 mRNA of Avian Reovirus

“…1B), encode the p10 fusion-associated small transmembrane proteins responsible for the syncytium-inducing phenotype of these fusogenic reoviruses (15). The p17 protein encoded by the second ORF is a nonstructural nucleocytoplasmic protein of no known function (16). With an A residue at position Ϫ3, the most conserved and functionally most important flanking residue, the ARV p17 start codon is in a strong context for translation initiation.…”