Regulators of cell death.

A novel oncogene-derived protein, Bcl-2, functions as a repressor of cell death in a genetic pathway of cellular suicide that appears to be common to all multicellular animals. A related protein that promotes cell death, Bax, wrestles with Bcl-2 through conserved motifs, BH1 and BH2, establishing a set point for these deaths. In Bcl-2-deficient mice, the ratio of these molecules is reset, resulting in massive cell death in several cell types.