The three proteins seemed to be part of an apoptosis system that has been highly conserved during evolution. A team at Massachusetts Institute of Technology subsequently cloned and sequenced another nematode cell death gene called CED9. It turned out to have a similar DNA sequence to human BCL-2. When ICE is over-expressed in mammalian cells, it causes apoptosis. BCL-2 inhibits cell death, while ICE kills cells.
Viruses can also carry cell-death genes.
Unfortunately, viruses that pick up apoptosis-inhibiting genes are at a selective advantage because they can keep the host cell alive while they replicate. The downside of apoptosis, says Dr Vaux, is that many cells suicide prematurely if they experience any sort of metabolic stress, such as oxygen deprivation after the blood supply is interrupted. He says knowledge of the genetic mechanisms of apoptosis could yield therapies to ameliorate brain and spinal cord damage after stroke or physical trauma, in which apoptosis can greatly magnify the impact of the primary lesion.