Sklenár V, Feigon J
Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.
Nature. 1990 Jun 28;345(6278):836-8. doi: 10.1038/345836a0.
Homopurine.homopyrimidine DNA sequences have been shown to form triple-stranded structures readily under appropriate conditions. Interest in DNA triplexes arises from potential applications of intermolecular triplexes as antisense inhibitors of gene expression and from the possibility that intramolecular triplexes may have a role in gene expression and recombination. We recently presented NMR evidence for triplex formation from the DNA oligonucleotides d(GA)4 and d(TC)4, which showed unambiguously that the second pyrimidine strand is Hoogsteen base paired and the cytosines are protonated at N3 as required. To obtain a more well defined triplex, and to provide a model for in vivo triplex structures, we have designed and synthesized a 28-base DNA oligomer with a sequence that could potentially fold to form a triplex containing both T.A.T and C+.G.C triplets. Our NMR results indicate that the conformation at pH 5.5 is an intramolecular triplex and that a significant amount of triplex remains even at pH 8.0.
同嘌呤-同嘧啶DNA序列已被证明在适当条件下很容易形成三链结构。对DNA三链体的兴趣源于分子间三链体作为基因表达反义抑制剂的潜在应用，以及分子内三链体可能在基因表达和重组中发挥作用的可能性。我们最近提供了来自DNA寡核苷酸d(GA)4和d(TC)4形成三链体的核磁共振证据，明确表明第二条嘧啶链是Hoogsteen碱基配对，并且胞嘧啶按要求在N3处质子化。为了获得更明确的三链体，并为体内三链体结构提供一个模型，我们设计并合成了一个28个碱基的DNA寡聚物，其序列可能折叠形成一个包含T.A.T和C⁺.G.C三联体的三链体。我们的核磁共振结果表明，pH 5.5时的构象是分子内三链体，甚至在pH 8.0时仍有大量三链体存在。
