Transcription factors DNA-binding activity in rat thymocytes undergoing apoptosis after heat-shock or dexamethasone treatment.

The onset of apoptosis is generally thought to require the induction of a novel genetic program. Accordingly, we studied the kinetic of DNA-binding activity of several transcription factors in rat thymocytes undergoing apoptosis induced by dexamethasone (DEX) or heat shock (HS) treatment. Here we report that: 1) early activation of AP-1 occurred in both models of apoptosis, even if the intensity of activation and AP-1 complex composition were different and much less evident in HS-treated thymocytes; 2) early NFkB DNA-binding activity was also observed in both types of apoptosis; 3) downregulation of other transcription factors, such as OCT-1 and CREB, with high constitutive activity, was recorded in both models of apoptosis. The fact that some TFs are up-regulated while others are down-regulated suggests that apoptosis is the result of a complex combination of positive and negative signals regulating gene expression.