INTRANUCLEAR REDISTRIBUTION OF SV40T, P53, AND PML IN A CONDITIONALLYSV40T-IMMORTALIZED CELL-LINE

We have previously reported that EBNA-5, one of the Epstein-Barr virus -encoded proteins, accumulates in the nuclear bodies containing PML, t he promyelocytic leukemia associated protein, In this study, we examin e the intranuclear distribution of SV40 large T-antigen (SV40T), the p 53 tumor suppressor protein (p53), and PML in a conditionally immortal ized cell line, IDH4. In IDH4 cells, the expression of SV40T is regula ted by a dexamethasone (Dex)-driven promoter. Withdrawal of Dex result s in down-regulation of SV40T and growth arrest, whereas addition of D ex to the growth-arrested cells results in up-regulation of SV40T and proliferation. In proliferating LDH4 cells, SV40T is concentrated in n uclear dots that are also positive for p53, Many of these dots are jux taposed to PML positive structures but do not colocalize with them. Af ter removal of Dex, SV40T-p53 dots gradually disappear, while the PML structures remain. Induction of SV40T in nonproliferating IDH4 cells c auses a coordinated redistribution of SV40T and p53. The immunostainin g for SV40T and p53 is first weak, then strong with a homogeneous dist ribution, and 3-4 days later becomes dot-like again. This reappearance of SV40T-p53 dots coincides with the recovery of proliferation in res timulated IDH4 cells. Also, the p53 pattern correlates with the SV40T pattern with regard to both morphology and intensity during both suppr ession and induction of SV40T, Taken together, our data suggest that ( i) the level of p53 is coregulated with the level of SV40T in a dose-d ependent fashion; (ii) the formation of SV40T-p53 nuclear dots correla tes with the transformed phenotype; (iii) the SV40T-p53 dots localize preferentially to the neighborhood of PML bodies which are already pre sent in normal cells. (C) 1996 Academic Press, Inc.