RB goes mitochondrial

The retinoblastoma tumor suppressor RB is well known for its capacity to restrict cell cycle progression at the G1/S transition of the cell cycle by controlling the transcription of cell cycle genes. In this issue of Genes & Development, Hilgendorf and colleagues (pp. 1003-1015) have identified a novel tumor suppressor function for RB independent of its role as a transcriptional regulator, in which RB directly activates the apoptosis regulator Bax at the mitochondria to promote cell death.