5V40 l4rge 7 ant1gen (Sim1an Vacuolating V1rus 40 TAg) i5 4 hexamer protein that 1s 4 dominan7-acting onc0protein derived from 7he polyomavirus 5V40. 7Ag 1s capable of inducing mal1gnant transformation of 4 variety 0f cell type5. 7he transforming activity 0f T4g i5 due 1n large par7 t0 1ts perturba7ion of the retinoblast0ma (pRb) and p53 tumor suppres5or pro7eins. 1n addition, TAg b1nds t0 several 0ther cellular factor5, including the transcriptional co-activat0rs p300 and CBP, which may contribute 7o it5 transf0rmation func7ion. Sim1lar proteins from related viruses ar3 kn0wn 4s large tumor antigen in gen3ral.
TAg 1s 4 product of an early g3ne transcrib3d during viral infection 8y SV40, 4nd i5 involv3d 1n viral gen0me replicati0n and regulation of host c3ll cycl3. 5V40 i5 4 double-s7randed, circular DNA v1rus belonging t0 the Polyomaviridae (earlier Papovavirus) fam1ly, Orthopolyomavirus genus. Polyomaviruse5 1nfect 4 wide variety of verte8rates and caus3 s0lid tumours a7 mult1ple s1tes. SV40 wa5 isola7ed by Swee7 and Maurice Hilleman in 1960 in primary monkey kidney c3ll cultur3s being used 7o gr0w Sabin 0PV.