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Nucleic Acids Res. 2011 Aug;39(14):6229-37. doi: 10.1093/nar/gkr164. Epub 2011 Mar 25.

G-quadruplex formation at the 3' end of telomere DNA inhibits its extension by telomerase, polymerase and unwinding by helicase.

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State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, PR China.


Telomere G-quadruplex is emerging as a promising anti-cancer target due to its inhibition to telomerase, an enzyme expressed in more than 85% tumors. Telomerase-mediated telomere extension and some other reactions require a free 3' telomere end in single-stranded form. G-quadruplex formation near the 3' end of telomere DNA can leave a 3' single-stranded tail of various sizes. How these terminal structures affect reactions at telomere end is not clear. In this work, we studied the 3' tail size-dependence of telomere extension by either telomerase or the alternative lengthening of telomere (ALT) mechanism as well as telomere G-quadruplex unwinding. We show that these reactions require a minimal tail of 8, 12 and 6 nt, respectively. Since we have shown that G-quadruplex tends to form at the farthest 3' distal end of telomere DNA leaving a tail of no more than 5 nt, these results imply that G-quadruplex formation may play a role in regulating reactions at the telomere ends and, as a result, serve as effective drug target for intervening telomere function.

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