[A large T-antigen of SV40 virus: involvement in replication of cellular DNA and interactions with nuclear proteins].

The SV40 large T-antigen is involved in transcription and replication of viral DNA and malignant cell transformation. In order to gain insight into its interaction with other proteins, we analyzed its distribution during the cell cycle using a cell-free system derived from Xenopus eggs that reproduces most nuclear events linked to the cell cycle in vitro. T-antigen associates with chromatin independently of the nuclear membrane formation. A transient association of T-antigen with the nuclear matrix is observed during ongoing DNA synthesis. However, T-antigen colocalizes neither with RPA pre-replication centers nor replication foci as detected by biotin dUTP labeling. Both intranuclear colocalization and biochemical interaction with the endogenous p53 were detected, which occurs at the nuclear matrix. These data are discussed in view of the T-antigen transforming activity.