Overcoming potassium-mediated triplex inhibition

Wendy M. Olivas, L. James Maher

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


Sequence-specific duplex DNA recognition by oligonucleotlde-dlrected triple helix formation Is a possible approach to In vivo gene inhibition. However, triple helix formation involving guanlne-rich oligo-nucleotides is Inhibited by physiological Ions, particularly K+, most likely due to oligonucleotide aggregation via guanine quartets. Three ollgodeoxynucleotlde (ODN) derivatives were tested for their ability to resist guanine quartet-mediated aggregation, yet form stable triplexes. Electrophoretic mobility shift and dimethyl sulfate footprinting assays were used to analyze the formation of triplexes Involving these oligonucleotide derivatives. In the absence of K+, all ODNs had similar binding affinities for the duplex target Triplexes involving a 14mer ODN derivative containing 7-deazaxanthine substituted for three thymine bases or an 18mer ODN containing two additional thymlnes on both the 5′ and 3′ termini were abolished by 50 mM K+. Remarkably, triplexes Involving an ODN derivative containing four 6-thloguanine bases substituted for guanine resisted K+ inhibition up to 200 mM. We hypothesize that the Increased radius and decreased electronegativity of sulfur in the 6-posltlon of guanine destabilize potential guanine quartets. These results improve the prospects for creating ODNs that might serve as specific and efficient gene repressors In vivo.

Original languageEnglish (US)
Pages (from-to)1936-1941
Number of pages6
JournalNucleic acids research
Issue number11
StatePublished - Jun 11 1995

ASJC Scopus subject areas

  • Genetics


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