de Bizemont T, Duval-Valentin G, Sun J S, Bisagni E, Garestier T, Hélène C
Laboratoire de Biophysique, CNRS URA 481, INSERM U 201, Paris, France.
Nucleic Acids Res. 1996 Mar 15;24(6):1136-43. doi: 10.1093/nar/24.6.1136.
Triple helix formation requires a polypurine- polypyrimidine sequence in the target DNA. Recent works have shown that this constraint can be circumvented by using alternate strand triplex-forming oligonucleotides. We have previously demonstrated that (T,G)-containing triplex- forming oligonucleotides may adopt a parallel or an antiparallel orientation with respect to an oligopurine target, depending upon the sequence and, in particular, upon the number of 5'-GpT-3' and 5'-TpG-3' steps [Sun et al. (1991) C.R. Acad. Sci. Paris Ser III, 313, 585-590]. A single (T,G)-containing oligonucleotide can therefore interact with two oligopurine stretches which alternate on the two strands of the target DNA. The (T,G) switch oligonucleotide contains a 5'-part targeted to one of the oligopurine sequences in a parallel orientation followed by a 3'-part that adopts an antiparallel orientation with respect to the second oligopurine sequence. We show that a limitation to the stability of such a triplex may arise from the instability of the antiparallel part, composed of reverse-Hoogsteen C.GxG and T.AxT base triplets. Using DNase I footprinting and ultraviolet absorption experiments, we report that a benzo[e]pyridoindole derivative [(3-methoxy- 7H-8-methyl-11-[(3'-amino-propyl) amino] benzo[e]pyrido [4,3-b]indole (BePI)], a drug interacting more tightly with a triplex than with a duplex DNA, strongly stabilizes triplexes with reverse-Hoogsteen C.GxG and T.AxT triplets thus allowing a stabilization of the triplex-forming switch (T,G) oligonucleotide on alternating oligopurine- oligopyrimidine 5'-(Pu)14(Py)14-3' duplex sequences. These results lead to an extension of the range of oligonucleotide sequences for alternate strand recognition of duplex DNA.
三链螺旋的形成需要靶DNA中存在聚嘌呤-聚嘧啶序列。最近的研究表明，通过使用交替链三链体形成寡核苷酸可以规避这一限制。我们之前已经证明，含（T，G）的三链体形成寡核苷酸相对于寡嘌呤靶标可能采取平行或反平行方向，这取决于序列，特别是取决于5'-GpT-3'和5'-TpG-3'步移的数量[Sun等人（1991年）《法国科学院学报》第三辑，313，585 - 590]。因此，单个含（T，G）的寡核苷酸可以与在靶DNA两条链上交替出现的两个寡嘌呤片段相互作用。（T，G）开关寡核苷酸包含一个5'部分，以平行方向靶向其中一个寡嘌呤序列，随后是一个3'部分，相对于第二个寡嘌呤序列采取反平行方向。我们表明，这种三链体稳定性的一个限制可能源于由反向Hoogsteen C.GxG和T.AxT碱基三联体组成的反平行部分的不稳定性。使用DNase I足迹法和紫外吸收实验，我们报告一种苯并[e]吡啶吲哚衍生物[（3-甲氧基-7H-8-甲基-11-[(3'-氨基丙基)氨基]苯并[e]吡啶[4,3-b]吲哚（BePI）]，一种与三链体比与双链DNA结合更紧密的药物，能强烈稳定具有反向Hoogsteen C.GxG和T.AxT三联体的三链体，从而使三链体形成开关（T，G）寡核苷酸在交替的寡嘌呤-寡嘧啶5'-(Pu)14(Py)14-3'双链序列上得以稳定。这些结果导致用于双链DNA交替链识别的寡核苷酸序列范围得以扩展。
