Expression profile and subcellular localization of Torque teno sus virus proteins

Abstract

In the present study, the expression, generation and subcellular localization of Torque teno sus virus (TTSuV) proteins were characterized into two genetically distinct TTSuV species (TTSuV1 and TTSuV2). Following transfection of three TTSuV1 and TTSuV2 full-length ORF (ORF1, ORF2 and ORF3) expression constructs into porcine kidney cells, alternative splice variants encoding new TTSuV protein isoforms were identified for the first time. Proteins encoded from ORF1 and ORF3 were localized in the nucleoli of porcine kidney cells and that of ORF2 in the cytoplasm and nucleus excluding the nucleoli. The subcellular localization of the different protein isoforms was not only similar between distinct TTSuV species but also to the ones described in human Torque teno virus (TTV). Results of the present in vitro study were not based on full-length viral clones but suggested that alternative splicing strategy to generate TTSuV protein isoforms probably occurs in vivo. Obtained data provide new information on molecular biology of TTSuV and anelloviruses, which until now has been solely based on results obtained from human TTV.

Rescue of a Porcine Anellovirus (Torque Teno Sus Virus 2) from Cloned Genomic DNA in Pigs

“…5), putative mRNA1, encoding full-length ORF1 of TTSuV2, was not detected (data not shown), which may suggest a smaller quantity and lower integrity of mRNA1 than of mRNA2 and mRNA3. In accordance with the result described by Martinez-Guinó et al, splicing of the 91-nt intron 2 sequence into mRNA3 also occurred posttranscription of the TTSuV2 ORF1-GFP fusion gene based on a non-fulllength viral clone (27).…”

“…The TTSuV2 ORF1 protein was expressed in cell nuclei, especially in nucleoli, which is consistent with the localization of human TTV ORF1 in Huh-7 cells transfected with the circular full-length TTV genomic DNA by immunoblotting with the ORF1-specific antibody (30). Most recently, it was also reported that TTSuV1 or TTSuV2 ORF1-GFP fusion protein expressed from the recombinant construct accumulated in the nucleoli of PK-15 cells (27).…”

Vaccination of pigs reduces Torque teno sus virus viremia during natural infection

“…The predominant transcripts detected in vitro and in vivo of ORF1 are spliced and full-length ORF1 transcripts have not been detected [5,6]. Splicing of TTSuVk2a ORF1 results in three protein isoforms (ORF1-A, -B and -C) and the amino acid composition between them varies, depending on the splicing site used [5,6].…”

“…ORF3 can only be translated after splicing of the mRNA precursor, and splicing of the ORF1 mRNA transcript results in different protein isoforms [5,6], as is also indicated in human TTV [7,8]. The predominant transcripts detected in vitro and in vivo of ORF1 are spliced and full-length ORF1 transcripts have not been detected [5,6]. Splicing of TTSuVk2a ORF1 results in three protein isoforms (ORF1-A, -B and -C) and the amino acid composition between them varies, depending on the splicing site used [5,6].…”

Development of an indirect ELISA assay for the detection of IgG antibodies against the ORF1 of Torque teno sus viruses 1 and 2 in conventional pigs

“…According to the International Committee on Taxonomy of Viruses (ICTV), the viral family comprises 11 genera, including human and animal anelloviruses. Anelloviruses are species specific, characterized by a high degree of genetic divergence, and similar genome organization and gene expression strategy (Martínez-Guinó et al, 2011;Okamoto et al, 2001).…”