Description_x000D_ Biochem/physiol Actions_x000D_ The large T antigen (TAg) of Simian virus 40 acts as an initiator of DNA replication, participates in cellular transformation, and induces cell growth. A number of functional domains have been characterized including the N-terminal J domain, nuclear localization signal (NLS), internal helicase domain, Rb and topoisomerase I interacting domain, p53 and ATP binding domain. The p53-interacting domain is also essential for binding p300/CBP. Phosphorylation of TAg by several kinases may regulate its function both positively and negatively._x000D_ The viral replication of simian virus 40 (SV40) is carried out by a single protein, T-antigen. This feature makes the virus a useful system for understanding the process of replication and to identify the components of replication machinery. It functions as a DNA helicase along with a cellular single-strand DNA binding protein and topoisomerase I or II, leading to extensive origin unwinding and formation of a pre-initiation complex. The T-antigen associates with two tumor suppressor proteins, p53 and the retinoblastoma protein pRb, and inactivates them._x000D_ Physical form_x000D_ Clear and colorless frozen liquid solution_x000D_ Preparation Note_x000D_ Use a manual defrost freezer and avoid repeated freeze-thaw cycles. While working, please keep sample on ice.