Hybridization of G-Quadruplex-Forming Peptide Nucleic Acids to Guanine-Rich DNA Templates Inhibits DNA Polymerase 畏 Extension

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• 作者：Connor T. Murphy ; Anisha Gupta ; Bruce A. Armitage ; Patricia L. Opresko
• 刊名：Biochemistry
• 出版年：2014
• 出版时间：August 19, 2014
• 年：2014
• 卷：53
• 期：32
• 页码：5315-5322
• 全文大小：352K
• ISSN：1520-4995

文摘

The guanine quadruplex (G-quadruplex) is a highly stable secondary structure that forms in G-rich repeats of DNA, which can interfere with DNA processes, including DNA replication and transcription. We showed previously that short guanine-rich peptide nucleic acids (PNAs) can form highly stable hybrid quadruplexes with DNA. We hypothesized that such structures would provide a stronger block to polymerase extension on G-rich templates than a native DNA homoquadruplex because of the greater thermodynamic stability of the PNA鈥揇NA hybrid structures. To test this, we analyzed the DNA primer extension activity of polymerase 畏, a translesion polymerase implicated in synthesis past G-quadruplex blocks, on DNA templates containing guanine repeats. We observed a PNA concentration-dependent decrease in the level of polymerase 畏 extension to the end of the template and an increase in the level of polymerase 畏 inhibition at the sequence prior to the G-rich repeats. In contrast, the addition of a complementary C-rich PNA that hybridizes to the G-rich repeats by Watson鈥揅rick base pairing led to a decrease in the level of polymerase inhibition and an increase in the level of full-length extension products. The G-quadruplex-forming PNA exhibited inhibition (IC₅₀ = 16.2 卤 3.3 nM) of polymerase 畏 DNA synthesis on the G-rich templates stronger than that of the established G-quadruplex-stabilizing ligand BRACO-19 (IC₅₀ = 42.5 卤 4.8 nM). Our results indicate that homologous PNA targeting of G-rich sequences creates stable PNA鈥揇NA heteroquadruplexes that inhibit polymerase 畏 extension more effectively than a DNA homoquadruplex. The implications of these results for the potential development of homologous PNAs as therapeutics for halting proliferating cancer cells are discussed.