DNA repair at telomeres: Keeping the ends intact

Themoleculareraoftelomere biology began withthe discovery that telomeres usually consist of G-rich simple repeats and end with 3⁰ single-stranded tails. Enormous progress has been made in identifying the mechanisms that maintain and replenish telomeric DNA and the proteins that protect them from degradation, fusions, and checkpoint activation. Although telomeresindifferent organisms (oreveninthe same organismunder different conditions) are maintained by different mechanisms, the disparate processes have the common goals of repairing defects caused by semiconservative replication through G-rich DNA, countering the shortening caused by incomplete replication, and postreplication regeneration of G tails. In addition,standardDNA repair mechanismsmustbesuppressedormodifiedattelomeresto preventtheirbeingrecognizedandprocessedasDNA double-strandbreaks.Here,wediscuss the players and processes that maintain and regenerate telomere structure.