PROGRAMMED CELL-DEATH - A MISSING LINK IS FOUND

Two families of proteins have advanced our understanding of the molecu lar basis of programmed cell death (PCD) in animal cells - the caspase s and Bcl-2-related proteins. While caspases lie at the heart of the d eath programme, Bcl-2-related proteins act as key intracellular regula tors. Although there has been considerable progress in elucidating the biochemical functions of caspases, how Bcl-2-related proteins regulat e caspase activation and thereby PCD, has remained a mystery. One key to resolving this mystery seems to lie with a new third family of prot eins related to the Caenorhabditis elegans cell-death protein CED-4, w hich connects Bcl-2-related proteins to caspases. An important step in defining this new family has been made by the identification of a hum an CED-4 homologue.