Cleavage of the serum response factor during death receptor-induced apoptosis results in an inhibition of the c-FOS promoter transcriptional activity

The c-FOS protooncogene is rapidly induced by a wide variety of extracellul ar stimuli including mitogenic signals. Regulation of c-FOS expression is t ightly dependent on the serum response element localized within its promote r. Two transcription factors, the serum response factor (SRF) and the terna ry complex factor, bind to the serum response element and play a key role i n the regulation of the c-FOS promoter activity. In the present study, we s how that two death effecters (CH11 and TRAIL) severely impaired the transcr iptional activity of the c-FOS promoter in Jurkat T cells. This inhibition can be accounted for by the specific cleavage by caspase 3 of the SRF both in vitro and in vivo, since acetyl-DEVD-aldehyde prevented SRF cleavage and abolished the inhibitory effect of CH11 and TRAIL on the c-FOS promoter ac tivity. Moreover, phorbol myristate acetate, a potent anti-apoptotic effect or, was found to protect SRF completely from cleavage by caspase 3 and also to prevent the inhibition of the c-FOS promoter activity by death effector s. Survival factors play an essential function in the regulation of cell gr owth mainly by regulating the expression of immediate early gene such as c- FOS. In this line, cleavage of SRF at the onset of apoptosis could abrogate the ability of the cell to induce inappropriate survival pathways. All tog ether, our results are consistent with a role of SRF at the interface betwe en cell survival and death pathways.