Table 1. Interactions of host cellular proteins with the ORFs of PCV2

PCV2 ORF	Host cell protein	Function of host cell protein	Biological meaning between specific ORF and host cell protein	Reference
ORF1 (Rep)	Syncoilin	Intermediate filament protein involved in transport processes	Transports viral proteins to subcellular organelles in host cells	[78]
	c-myc	Transcription factor which promotes cell cycle progress and DNA replication	Initiates viral DNA replication	[78]
	TDG	Thymidine DNA glycosylase associated in G/T mismatch repair	Participates in viral DNA replication	[79]
	VG5Q	Angiogenic factor which regulates vascular development	Unknown	[79]
	ZNF265	Subunit of pre-mRNA spliceosome required for alternative splicing	Affects transcription and viral mRNA splicing	[79]
ORF2 (Cap)	P-selectin	Cell adhesion molecule involved in an interaction between endothelial cells and leukocytes	Facilitates viral attachment and entry into host cells	[78]
	C1qBP	Complement factor which binds with the globular heads of C1q	Mediates phagocytosis and production of proinflammatory cytokines	[78,79,103,104]
	Hsp40	Chaperone which delivers unfolded and misfolded proteins to Hsp70	Assists Hsp70 to enhance progeny virus production	[79]
	Hsp70	Chaperone involved in protein folding	Increases progeny virus production by elevating PCV2 genome replication	[107]
	MKRN1	RNA-binding E3 ubiquitin ligase which modulates cell cycle or senescence	Unknown	[79]
	NAP1	Histone chaperone which participates in nucleosome assembly	Unknown	[79]
	NPM1	Nucleolar protein shuttling between nucleus and cytoplasm	Unknown	[79,116]
	Par-4	Caspase-3 substrate	Promotes apoptosis in host cells	[79]
	DDX21	RNA helicase involved in ribosomal RNA processing	Unknown	[116]
	EIF4A2	RNA helicase which is a component of eIF4F complex	Unknown	[116]
	hnRNPC	RNA-binding protein which regulates RNA homeostasis	Unknown	[116]
	IC1	Protease inhibitor which has anti-inflammatory effects	Participates in local inflammation	[116]
	IPO5	Nuclear transport receptor which belongs to importin beta family	Unknown	[116]
	MX2	IFN-induced GTPase interfering with viral capsid transport	Blocks the progeny virus production	[116]
	SNAI2	Transcription factor upregulating cell differentiation and migration	Unknown	[116]
ORF3	Pirh2	E3 ubiquitin ligase involved in proteasomal degradation of p53	Causes apoptosis by increasing half-life of p53	[127,128]
	DDE-like transposase	Transposase catalyzing the movement of DNA segments	Unknown	[78]
	RGS16	G protein signaling inhibitor which suppresses NFκB translocation	Promotes inflammatory responses by degradation of RGS16	[78,132,133]
ORF4	FHC	Ferroxidase which removes reactive oxygen intermediates	Rescues host cells from apoptosis	[137]
	ANT3	Translocase that mediates ADP/ATP exchange in mitochondrial matrix and cytosol	Leads to apoptosis by mitochondrial damage	[139]
	COX8A	Component of COX involved in the hydrogen transfer in mitochondria	Unknown	[137]
	SNRPN	Polypeptide associated with pre-mRNA splicing	Unknown	[137]
	Lamin C	Type V intermediate filament protein which is a major component of the nuclear lamina	Unknown	[137]
ORF5	CYP1A1	Member of the cytochrome P450 which functions as monooxygenases	Unknown	[144]
	GPNMB	Type l transmembrane glycoprotein associated with cell proliferation and anti-inflammatory responses	Inhibits viral replication	[144,150]
	SRSF3	Pre-mRNA splicing factor which promotes exon-inclusion during alternative splicing	Unknown	[144]
	YWHAB	Adaptor protein which facilitates cell proliferation	Prevents PCV2-induced autophagy and apoptosis	[144,151]
	ZNF511	Transcription factor interacting with RNA polymerase ll	Unknown	[144]

ORF, open reading frame; PCV2, porcine circovirus type 2; ADP/ATP, adenosine diphosphate/adenosine triphosphate.