[Telomeres enable cells to distinguish natural chromosome ends from damaged DNA because uncapped telomeres elicit a DNA damage response that halts cell proliferation. The protection of human chromosome ends primarily depends on the telomeric protein TRF2 and telomere capping involves the formation of a higher order structure, the telomeric loop or t-loop. Telomeres consist of a tandem array of telomeric DNA repeats bound to specialized telomeric proteins. Telomerase activity lengthens terminal regions of eukaryotic telomeric DNA by RNA-templated addition of repeated DNA sequences. Active telomerase forms a structure at the telomere that prevents chromosome ends from being sensed as DNA damage. Telomerase is regulated by sequence-specific DNA binding proteins that bind telomeric DNA repeats. Through separate domains, these proteins bind additional proteins to assemble a higher-order complex on the telomeric DNA. (from PMID 11850778 and NCI) ( NCI )]
UMLS (NCI) C1155299