Shelterin

Shelterin (also called telosome) is a protein complex known to protect mammalian telomeres from DNA repair mechanisms, as well as regulate telomerase activity. In mammals and other eukaryotes, telomeric DNA consists of double- and single-stranded TTAGGG repeats and a single-stranded, G-rich overhang. Subunits of shelterin bind to these regions and induce the formation of a t-loop, a cap structure that deters DNA-damage-sensing machinery from mistakenly repairing telomeres. The absence of shelterin causes telomere uncapping and thereby activates damage-signaling pathways that may lead to non-homologous end joining (NHEJ), homology directed repair (HDR), senescence, or apoptosis.