Telomeres: Maintenance and Replication

Telomeres are specialized protein–DNA complexes at the ends of eukaryotic chromosomes that carry out two essential functions. Telomeres cap chromosome ends, preventing the cell from recognizing them as accidental DNA breaks. Telomeres also prevent erosion of chromosome ends following conventional DNA replication, which initiates with an RNA primer whose removal cannot be repaired DNA ends. In nearly all eukaryotes this problem is solved by the telomerase enzyme, which adds short DNA repeats de novo onto chromosome ends in a regulated fashion. Because of these unique features, telomere biology has important implications in aging and in human disease, most notably in the development of tumors.