THE CASPASE-RB CONNECTION IN CELL-DEATH

Execution of the cell-death programme requires the activation of a fam ily of cysteine proteases known as caspases. Specific cellular protein s are cleaved by caspases during apoptosis, including the retinoblasto ma tumour-suppressor protein (RB1). A caspase-resistant RB1 can attenu ate the death response to tumour necrosis factor alpha. The cleavage o f RB1 during cell death, together with the increased cell death during embryonic development of Rb-knockout mice, suggests that RB1 degradat ion contributes to the activation of the cell-death pathway.