Spectroscopic investigation of an intramolecular DNA triplex containing both G.G:C and T.A:T triads and its complex with netropsin
Spectroscopic investigation of an intramolecular DNA triplex containing both G.G:C and T.A:T triads and its complex with netropsin
复制标题
DOI：
10.1080/07391102.1998.10509007
复制
发表时间：
1998-06-01
影响因子：
4.4
通讯作者：
Durand, M
中科院分区：
文献类型：
--
作者：
Gondeau, C;Maurizot, JC;Durand, M
用紫外吸收光谱和圆二色性研究了寡核苷酸（5′）d(G(4)T(4)G(4)- [T-4]-G(4)A(4)G(4)- [T-4]- c4t4c4 （[T-4]代表4个胸腺嘧啶残基的一段）形成的三螺旋结构。在10 mM的乙酸钠，0.2 mM的EDTA二钠（pH 7）缓冲液中，我们得到了以下显著的结果：1)在没有MgCl2的情况下，寡核苷酸呈发夹双链结构，具有悬尾（5’）d(G(4)T（4)G(4)-[T-4]）。这个5'末端，包含四个鸟嘌呤残基的分离运行，不假设当这个序列自由时所观察到的预期的四联构象。ii)在MgCl2存在的情况下，寡核苷酸通过双发夹结构折叠两次，形成三螺旋结构，带有[T-4]单链环；iii)向预形成的三螺旋结构中加入高浓度的KCl不会破坏结构。然而，如果允许寡核苷酸在K+存在下折叠，则三倍体的形成受到抑制。圆二色性研究表明，寡核苷酸通过端粒（5’）d(G（4)T（4)G(4)-[T-4]）末端形成反平行的G-四聚体，形成二聚体构象。iv）在本报告使用的实验条件下，三聚体以单相方式熔化；v) Netropsin，一种DNA小槽配体；在等摩尔化学计量中与双链的中心位点A(4)/T-4和三链的中心位点结合。与以往有关pyr的研究相反。Pur:pyr三聚体，热变性实验表明，netropsin结合稳定了分子内三聚体。
The triple helix formation by the oligonucleotide (5')d(G(4)T(4)G(4)- [T-4]-G(4)A(4)G(4)- [T-4]-C4T4C4) ([T-4] represents a stretch of 4 thymine residues) has been investigated by UV absorption spectroscopy and circular dichroism. In a 10 mM sodium cacodylate, 0.2 mM disodium EDTA (pH 7) buffer, we show: the following significant results: i) in the absence of MgCl2, the oligonucleotide adopts a hairpin duplex structure with the dangling tail (5')d(G(4)T(4)G(4)-[T-4]). This 5' extremity, which contains separated runs of four guanine residues, does not assume the expected tetraplex conformation observed when this sequence is free. ii) In the presence of MgCl2, the oligonucleotide folds back on itself twice to give a triple helix via a double hairpin formation, with [T-4] single-strand loops, iii) The addition of high concentration of KCl to the preformed tripler does not disrupt the structure. Nevertheless, if the oligonucleotide is allowed to fold back in the presence of K+, tripler formation is inhibited. Circular dichroism studies demonstrate that the oligonucleotide adopts a dimeric conformation, resulting from the association of two hairpin duplexes, via the formation of an antiparallel G-quadruplex by the telomeric (5')d(G(4)T(4)G(4)-[T-4]) extremities, iv) Under the experimental conditions used in this report, the tripler melts in a monophasic manner, v) Netropsin, a DNA minor groove ligand, binds to the central site A(4)/T-4 of the duplex and to that of the tripler in an equimolar stoichiometry. In contrast with previous studies concerning pyr.pur:pyr triplexes, thermal denaturation experiments demonstrate that the netropsin binding stabilizes the intramolecular tripler.