The multifunctional SV40 large T antigen is sufficient to transform actively growing cells in culture. Among Tantigen activities is the ability to transactivate RNA polymerase l-dependent ribosomal gene promoters. Transactivation of ribosomal genes may enable cells to manage the increased demand for protein synthesis that accompanies transformation. The overall goal of this research is to define activities of T antigen involved in transactivation of ribosomal gene promoters. We showed previously that the ability of T antigen to overcome the species-specificity barrier for transactivation is independent of Rb-binding but dependent on one or more J-domain activities, the nuclear localization signal and amino acids surrounding it, and a contiguous portion of T antigen spanning amino acids 109-626. During the past funding period we showed, that T antigen mediated transactivation of the rat ribosomal promoter is independent of p53-binding and yet, transactivation in a more closely related species, the mouse, is independent of the J-domain and Rb-binding. In both cell systems the T antigen activities required to transactivate ribosomal promoter paralleled those required to transactivate the cyclin A promoter. The experiments described here extend those investigations by defining fully the region/activities of T antigen localized to amino acids 109-626; including an extensive analysis of the J-domain, the region surrounding the NLS, the DNA-, and p53-binding region. Transactivation of the cyclin A promoter will be assessed in parallel to determine if the T antigen activities responsible for transactivation of the ribosomal and cyclin A promoters are separable. Additionally, we will assess T antigen activities needed to reactivate silent ribosomal genes by using an inducible and/or conditionally expressed T antigen system. Finally, preliminary experiments will be undertaken to investigate the relationship between T antigen, Ku, and its associated kinase. The experiments serve the goal of training of undergraduate students, and furthering our knowledge of the activities needed for T-antigen mediated transformation, and is well within capabilities of the investigator and the facilities of Elizabethtown College. ? ?
| Cavender, J F; Mummert, C; Tevethia, M J (1999) Transactivation of a ribosomal gene by simian virus 40 large-T antigen requires at least three activities of the protein. J Virol 73:214-24 |
