Simian virus 40 T antigen induces p53-independent apoptosis but does not suppress erbB2/neu gene expression in immortalized human epithelial cells

Previously, we have shown that simian virus 40 (SV40) T antigen can directly cause apoptosis in immortalized human epithelial cells under normal growth conditions. In this study, we further characterized the mechanism of T-antigen-mediated apoptosis involving p53 and whether T antigen can suppress erbB2/neu gene expression. Our results show the differential regulation of erbB2/neu gene expression in different cell clones in response to T antigen transgene, indicating that the regression of erbB2/neu gene by SV40 T is cell-type dependent. Our previous study reported T-antigen-induced apoptosis in p53 mutant cells; however, in this study we find increased levels of p53 protein in T-antigen-containing cells. Therefore, we examined the transactivation function of p53 in these cells. Our data show the failure to transactivate p53, suggesting that increased p53 protein in T antigen expressing cells is functionless at least for transcriptional activation.