Telomeric and Subtelomeric Repeat Sequences


Telomeric repeats are the tandem arrays of a short G‐rich sequence that are present at the ends of most eukaryotic chromosomes. Subtelomeric sequences lie immediately proximal to the telomeric repeats and are composed of complex patchwork of low‐copy repeated sequences, segmental duplications and degenerate telomeric repeats.

Keywords: chromosome ends; telomere; subtelomere; repeated sequence DNA; genome stability; interchromosomal recombination

Figure 1.

Organization of mammalian telomeric DNA. (a) Arrangement of the telomeric repeats at a chromosome end. (b) Structure of a t‐loop. 3′ and 5′ refer to the ends of the G‐ and C‐rich strands, respectively.

Figure 2.

Telomeric G‐strand overhang can form high‐order structures stabilized by nonWatson–Crick interactions between guanines. (a) The G‐quartet, a planar, cyclic arrangement of four guanine bases each donating and accepting two hydrogen bonds (red). The stacking of G‐quartets results in the formation of G‐quadruplexes, (b) and (c), which are stabilized by monovalent metal ions located in the central cavity (grey spheres). (b) Intramolecular G‐quadruplex formed by folding of a single oligonucleotide 5′‐A(GGGTTA)3GGGT‐3′. (c) Intermolecular G‐quadruplex with antiparallel strands formed by dimerization of two oligonucleotides each folded in a hairpin – a model for telomere–telomere association.

Figure 3.

Organization of the subtelomeric domains. Four regions are shown with the telomeric repeats at the top of the figure. The distal subtelomeric sequence contains short sequences common to many chromosomes. The arrow marks a DNA loop from one chromosome interacting with another. The proximal subtelomeric sequence consists of long sequences common to a few chromosomes (marked by dotted lines). The degenerate T2AG3 repeats mark the boundary between the distal and proximal subtelomeric sequence (ARS, autonomous replicating sequence). Reproduced from Flint et al. with permission from Oxford University Press.



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Further Reading

Ambrosini A, Paul S, Hu S and Riethman H (2007) Human subtelomeric duplicon structure and organization. Genome Biology 8: R151.

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Mewborn SK, Lese Martin C and Ledbetter DH (2005) The dynamic nature and evolutionary history of subtelomeric and pericetromeric regions. Cytogenetic and Genome Research 108: 22–25.

Riethman H, Ambrosini A and Paul S (2005) Human subtelomere structure and variation. Chromosome Research 13: 505–515.

Riethman HC, Xiang Z, Paul S et al. (2001) Integration of telomere sequences with the draft human genome sequence. Nature 409: 948–951.

Smogorzewska A and de Lange T (2004) Regulation of telomerase by telomeric proteins. Annual Review of Biochemistry 73: 177–208.

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Churikov, Dmitri, and Price, Carolyn M(Jul 2008) Telomeric and Subtelomeric Repeat Sequences. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0005065.pub3]