Essential role for p53-mediated transcription in E1A-induced apoptosis.

Baby rat kidney (BRK) cell lines transformed by E1A and a temperature-sensitive p53 [tsp53(val135)] undergo rapid apoptosis when p53 assumes the wild-type conformation at the permissive temperature. Wild-type p53 function is therefore required for induction of apoptosis in response to growth deregulation by E1A. BRK cells transformed by E1A and a transcriptionally defective temperature-sensitive p53 [tsp53(22-23val135)] are dramatically impaired for the ability to mediate E1A-induced apoptosis at the permissive temperature. The tsp53(22-23val135), however, still retains some ability to suppress cell growth. Thus, the activity of p53 as a transcription factor is directly correlated with the ability of E1A to induce apoptosis. In addition, there may exist at least two different mechanisms by which p53 can suppress cell-cycle progression, only one of which is dependent on p53-mediated transcription.