The Porcine Circovirus Type 2 Nonstructural Protein ORF3 Induces Apoptosis in Porcine Peripheral Blood Mononuclear Cells



Wei-Li Lin 1, Maw-Sheng Chien 2, Pei-Ching Wu 1, Chen-Li Lai 1, Chienjin Huang*, 1
1 Graduate Institute of Microbiology and Public Health, College of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan
2 Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan


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© Lin et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http: //creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Graduate Institute of Microbiology and Public Health, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 40227, Taiwan, Republic of China; Tel: + 886 4 22853906; Fax: + 886 4 22851741; E-mail: cjhuang@dragon.nchu.edu.tw


Abstract

Porcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus-associated diseases in pigs. To analyze whether the PCV2 nonstructural protein ORF3 is able to induce apoptosis in nature target cells, transient expression of ORF3 in porcine peripheral blood mononuclear cells (PBMC) was performed, and apoptosis was confirmed by terminal dexoynucleotidyl transferase (TdT)-mediated BrdUTP-nick end labeling (TUNEL) assay. The apoptotic responses induced by the full length or the C-terminal half of ORF3 were significantly higher (p < 0.001) than that of cells transfected with the control plasmid. In contrast, the N-terminal half of ORF3 restrictively localized in the cytoplasm and remarkably reduced its ability to induce apoptosis, the apoptotic activity might be correlated with the nuclear localization of ORF3. Furthermore, two clusters of basic residues on the C-terminal half region at the amino acid residues 53-68 and 85-104 could mediate the nuclear localization of fusion protein, confirming their potential role as a nuclear localization signal.

Keywords: Apoptosis, Nuclear localization signal, ORF3 protein, Porcine circovirus type 2, Transient expression..