SV40 T Ag [Pab101]

Simian virus 40 is a small DNA virus encoded by 5.2 kb of double-stranded DNA. SV40 large T antigen (T-ag) is a multifunctional ~85 kD phosphoprotein, which is the sole viral protein required for SV40 replication. All other factors are provided by the infected host cell. In addition to its role in SV40 DNA replication, T-ag also causes transformation of susceptible cell lines. Studies of various mutant T-ag proteins have shown that the replication and transformation fractions of T-ag can be separated. The multifunctional nature of this protein has resulted in its use as a model system in a wide variety of disciplines. However, all functions of T-ag are influenced by a wide range of post-translational modifications including phosphorylation, glycosylation, acetylation, acylation and adenylation. T-ag exists in monomeric as well as polymeric forms and associates with the tumor suppressor proteins p53 and Rb (retinoblastoma protein). Most of T-ag is transported to the nucleus, while a small fraction is localized at the cell surface.