To isolate the apoptosis-linked genes involved in the cell death of thymocytes induced by glucocorticoids, we developed a functional cloning assay. Murine CD4+CD8+ thymic cell line 2-257-20 cells were transfected with cDNA expression libraries obtained from a dexamethasone-resistant cell line. The transfected cells were selected in the presence of dexamethasone, and the plasmids which episomally expanded were then extracted from the surviving cells. One of the rescued cDNAs was found to be an antisense cDNA fragment identical to the mouse mitochondrial ATPase 6 gene. In the stable transfectants with the ATPase 6 antisense gene, the induction of apoptosis by dexamethasone was significantly delayed. Furthermore, the ATP synthesis in these transfectants was also reduced to some extent. ATPase 6 is a subunit of FoF1 ATPase and our results support that ATP synthesis from the mitochondria is necessary for the induction of apoptosis induced by glucocorticoids.
