Telomeres: More than chromosomal non-sticking ends

Telomeres are specialized natural ends of eukaryotic chromosomes that, cont rary to the ends of broken chromosomes, are stable and do not fuse with the ends of other chromosomes. In addition, telomeres protect chromosomal ends from degradation, facilitate completion of chromosomal DNA replication, an d contribute to chromosome positioning within nuclei. Telomeric DNA consist s of repetitive sequences and specific associated proteins, including the t elomere repeat-binding factors TRF1 and TRF2. A lack of TRF2 enables end-to -end chromosome fusion. A structural disruption of telomeres not only cause s chromosomal mechanical instability but also activates a programmed cell d eath cascade. (C) 2000 Wiley-Liss, Inc.