Cellular senescence, cancer and aging: the telomere connection

Telomeres are the repetitive DNA sequences and specialized proteins that fo rm the distinctive structure that caps the ends of linear chromosomes. Telo meres allow cells to distinguish the chromosome ends from double strand DNA breaks. The telomeric structure prevents the degradation or fusion of chro mosome ends, and thus is essential for maintaining the integrity and stabil ity of eukaryotic genomes. In addition, and perhaps less widely appreciated , telomeres may also indirectly influence gene expression. The length, stru cture and organization of telomeres are regulated by a host of telomere-ass ociated proteins, and can be influenced by basic cellular processes such as cell proliferation, differentiation, and DNA damage. In mammalian cells, t elomere length and/or telomere structure have been linked to both cancer an d aging. Here, we briefly review what is known about mammalian telomeres an d the proteins that associate with them, and discuss the cellular and organ ismal consequences of telomere dysfunction and the evidence that cells with dysfunctional telomeres. can contribute to cancer and aging phenotypes. (C ) 2001 Published by Elsevier Science Inc.