p16 and ARF: activation of teenage proteins in old age

Cellular senescence induced by different stresses and telomere shortening appears to play an important role in the aging process. The products of the INK4a/ARF locus — p16INK4a and ARF — arrest cell proliferation at the senescence stage by exerting their effects on retinoblastoma protein– and p53-mediated responsive pathways. A study in this issue of the JCI provides experimental evidence of a specific upregulation of these cell cycle inhibitors in a variety of organs during mammalian aging.