Telomeric repeat mutagenicity in human somatic cells is modulated by repeat orientation and G-quadruplex stability

Rama Rao Damerla, Kelly E. Knickelbein, Devin Kepchia, Abbe Jackson, Bruce A. Armitage, Kristin A. Eckert, Patricia L. Opresko

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Telomeres consisting of tandem guanine-rich repeats can form secondary DNA structures called G-quadruplexes that represent potential targets for DNA repair enzymes. While G-quadruplexes interfere with DNA synthesis in vitro, the impact of G-quadruplex formation on telomeric repeat replication in human cells is not clear. We investigated the mutagenicity of telomeric repeats as a function of G-quadruplex folding opportunity and thermal stability using a shuttle vector mutagenesis assay. Since single-stranded DNA during lagging strand replication increases the opportunity for G-quadruplex folding, we tested vectors with G-rich sequences on the lagging versus the leading strand. Contrary to our prediction, vectors containing human [TTAGGG]10 repeats with a G-rich lagging strand were significantly less mutagenic than vectors with a G-rich leading strand, after replication in normal human cells. We show by UV melting experiments that G-quadruplexes from ciliates [TTGGGG]4 and [TTTTGGGG]4 are thermally more stable compared to human [TTAGGG]4. Consistent with this, replication of vectors with ciliate [TTGGGG]10 repeats yielded a 3-fold higher mutant rate compared to the human [TTAGGG]10 vectors. Furthermore, we observed significantly more mutagenic events in the ciliate repeats compared to the human repeats. Our data demonstrate that increased G-quadruplex opportunity (repeat orientation) in human telomeric repeats decreased mutagenicity, while increased thermal stability of telomeric G-quadruplexes was associated with increased mutagenicity.

Original languageEnglish (US)
Pages (from-to)1119-1129
Number of pages11
JournalDNA Repair
Issue number11
StatePublished - Nov 10 2010

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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