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J Phys Chem B. 2013 Oct 3;117(39):11584-95. doi: 10.1021/jp4064966. Epub 2013 Sep 18.

Effects of hypoxanthine substitution in peptide nucleic acids targeting KRAS2 oncogenic mRNA molecules: theory and experiment.

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  • 1Departments of Biochemistry & Molecular Biology and ∥Radiology, and ⊥Kimmel Cancer Center, Thomas Jefferson University , Philadelphia, Pennsylvania 19107, United States.

Abstract

Genetic disorders can arise from single base substitutions in a single gene. A single base substitution for wild type guanine in the twelfth codon of KRAS2 mRNA occurs frequently to initiate lung, pancreatic, and colon cancer. We have observed single base mismatch specificity in radioimaging of mutant KRAS2 mRNA in tumors in mice by in vivo hybridization with radiolabeled peptide nucleic acid (PNA) dodecamers. We hypothesized that multimutant specificity could be achieved with a PNA dodecamer incorporating hypoxanthine, which can form Watson-Crick base pairs with adenine, cytosine, thymine, and uracil. Using molecular dynamics simulations and free energy calculations, we show that hypoxanthine substitutions in PNAs are tolerated in KRAS2 RNA:PNA duplexes where wild type guanine is replaced by mutant uracil or adenine in RNA. To validate our predictions, we synthesized PNA dodecamers with hypoxanthine, and then measured the thermal stability of RNA:PNA duplexes. Circular dichroism thermal melting results showed that hypoxanthine-containing PNAs are more stable in duplexes where hypoxanthine-adenine and hypoxanthine-uracil base pairs are formed than single mismatch duplexes or duplexes containing hypoxanthine-guanine opposition.

PMID:
23972113
[PubMed - indexed for MEDLINE]
PMCID:
PMC3946533
Free PMC Article
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