Telomeres are unique protein–DNA structures that comprise the termini of eukaryotic linear chromosomes (for review see references 1, 2). Telomeric DNA does not contain protein-encoding genes but rather consists of G-rich hexanucleotide repeats that in vertebrate cells are (TTAGGG)n sequences. Based on studies initially carried out in yeast and other single cell organisms, it appears that telomere functions include the stabilization and protection of chromosomal ends from events such as illegitimate recombination, the determination of chromosomal localization within the nucleus, and the regulation of cellular replicative capacity. It is this last function, the role of telomeres in regulation of replicative capacity, that has received particular attention in studies of cellular senescence and organismal aging.
A pivotal finding in the understanding of somatic cell biology was the observation that normal somatic cells have a finite replicative life...
