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아래의 내용을 참고 하세요. 즉, SV40-T antigen의 대표적 기능으로, 숙주세포의 RNA polymerase II에 의해 직접 transcription 되고, TAg는 SV40 orgin과 결합하며 또한 숙주 세포내의 DNA polymerase와 결합하여 DNA replication을 향상시키는 역할을 합니다. 따라서 transforming activity가 강력하므로 일반적으로 report vector 및 expression vector 등에 주로 사용되어집니다. SV40 (Simian Vacuolating Virus 40) large T antigen (TAg) is a powerful oncoprotein capable of transforming a variety of cell types. The transforming activity of TAg is due in large part to its perturbation of the retinoblastoma (pRB) and p53 tumor suppressor proteins. In addition, TAg binds to several other cellular factors, including the transcriptional co-activators p300 and CBP, which may contribute to its transformation function. TAg is a product of an early gene transcribed during viral infection by SV40, and is involved in viral genome replication and regulation of host cell cycle. SV40 is a double-stranded DNA virus, belongs to Papovavirus family, Polyomavirus genus. Polyomaviruses infect a wide variety of vertebrates and it caused solid tumours at multiple sites. SV40 was isolated by Sweet and Hilleman in 1960 in primary monkey kidney cells cultures being used to grow Sabin OPV. Mechanism: After entering the cell, the virus genes are transcribed by host cell RNA polymerase II to produce early mRNAs. Because of the relative simplicity of the genome, polyomaviruses are heavily dependent on the cell for transcription and genome replication. The cis-acting regulatory element surrounding the origin of replication directs transcription, and T-antigen directs transcription and replication. SV40 DNA replication is initiated by binding of large T-antigen to the origin region of the genome. The function of T-antigen is controlled by phosphorylation, which attenuates the binding to the SV40 origin. Protein-protein interactions between T-antigen and DNA polymerase-alpha directly stimulate replication of the virus genome. T-antigen also binds and inactivates tumor suppressor proteins (p53, p105). This causes the cells to leave G1 phase and enter into S phase, which promotes DNA replication. The SV40 genome is very small and does not encode all the information necessary for DNA replication. Therefore, it is essential for the host cell to enter S phase, when cell DNA and the virus genome are replicated together. Therefore, in addition to increasing transcription, another function of T-antigen is to alter the cellular environment to permit virus genome replication. http://www.mcb.uct.ac.za/cann/335/Papovaviruses.html 출처: Wikipedia