Telomeres: more than chromosomal non-sticking ends.

Telomeres are specialized natural ends of eukaryotic chromosomes that, contrary 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, and contribute to chromosome positioning within nuclei. Telomeric DNA consists of repetitive sequences and specific associated proteins, including the telomere repeat-binding factors TRF1 and TRF2. A lack of TRF2 enables end-to-end chromosome fusion. A structural disruption of telomeres not only causes chromosomal mechanical instability but also activates a programmed cell death cascade.