Table 1.

Antisense transcription activity in endogenous and exogenous retroviruses

Retrovirus	Genus	Species	Bidirectional LTR	Antisense transcript	Distribution and function of transcript	Antisense protein	Distribution and function of protein
Exogenous	Gamma-	MLV	P	?	?	?	?
	Delta-	HTLV-1	P	Hbz	Primarily nucleus Promotes cell survival and proliferation Encodes HBZ	HBZ	Nucleus Promotes viral latency and persistence
		HTLV-2	P	Aph-2	Unknown distribution Encodes APH-2	APH-2	Nucleus Inhibits viral replication
		HTLV-3	P	Aph-3	?	APH-3	Nucleus, cytoplasm Inhibits LTR activity
		HTLV-4	P	Aph-4	?	APH-4	Nucleus Inhibits LTR activity
		STLV	P	Sbz	?	SBZ	Nucleus Promotes viral latency and persistence
		BLV	P	AS1, AS2	Nucleus Promote cell proliferation	O	O
	Lentiviruses	HIV-1 (M)	P	Ast, ASP RNA	Primarily nucleus Promotes latency Encodes ASP	ASP	Nucleus, cytoplasm, cell surface, viral envelope Unknown role
		FIV	P	P	?	O	O
		BIV	P	P	?	O	O
Endogenous	Class I	HERV1	P	?	?	O	O
		HERV9	P	?	?	O	O
	Class II	HERV-K	P	P	?	O	O
		muIAP	P	P	?	O	O
	Class III	muERV-L	P	P	?	O	O

Gamma- = Gammaretroviruses; Delta- = Deltraretroviruses; ? = unknown, not reported; P = reported, confirmed; O = absent, not found