ISOLATION OF DAP3, A NOVEL MEDIATOR OF INTERFERON-GAMMA-INDUCED CELL-DEATH

Interaction of certain cytokines with their corresponding cell-surface receptors induces programed cell death. Interferon-gamma induces in H eLa cells a type of cell death with features characteristic of program ed cell death. Here, we report the isolation of a novel gene, DAP3 (de ath-associated protein-3), involved in mediating interferon-gamma-indu ced cell death. The rescue of this gene was performed by a functional selection approach of gene cloning that is based on transfection with an antisense cDNA expression library, The antisense RNA-mediated inact ivation of the DAPS gene protected the cells from interferon-gamma-ind uced cell death. This property endowed the cells expressing it with a growth advantage in an environment restrictive due to the continuous p resence of interferon-gamma and thus provided the basis of its selecti on, The gene is transcribed into a single 1.7-kilobase mRNA, which is ubiquitously expressed in different tissues and codes for a 46-kDa pro tein carrying a potential P-loop motif. Ectopic expression of DAP3 in HeLa cells was not compatible with cell growth, resulting in a 16 fold reduction in the number of drug-resistant stable clones. The data pre sented suggest that DAP3 is a positive mediator of cell death induced by interferon-gamma.