TOPOLOGY AND FORMATION OF TRIPLE-STRANDED H-DNA
TOPOLOGY AND FORMATION OF TRIPLE-STRANDED H-DNA
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DOI：
10.1126/science.2648571
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发表时间：
1989-03-24
期刊：
影响因子：
56.9
通讯作者：
DAHLBERG, JE
中科院分区：
文献类型：
--
作者：
HTUN, H;DAHLBERG, JE
(dt-dc)n.碳纳米点的重复共聚物。(da-dg)n个序列(TC.cntdo.AgN)可以呈现由三链和单链区域组成的铰链DNA结构(H-DNA)。通过对具有不同长度(Tc.cntpoint)的S DNA进行双向凝胶电泳分析，提出了H-DNA形成的模型。Ag)n共聚物。在这个模型中，H-DNA的形成是在共聚物内部的一个小变性气泡开始的，这使得两边的双链略有旋转并折叠回来，以形成第一个碱基三联体。这种成核作用确定了几种不同的H-DNA构象中的哪一种将被任何DNA分子采用，从而将每个分子捕获到几种不可自由相互转化的亚稳构象中的一种。随后，受体区域通过供体区域的渐进性变性释放单链多嘧啶，缠绕和变性都会导致DNA分子其余部分的负超螺旋松弛。从模型中可以预测，DNA的超卷曲程度决定了(dt-dc)n重复序列的哪一半将成为捐赠的第三链。
Repeating copolymers of (dT-dC)n .cntdot. (dA-dG)n sequences (TC .cntdot. AGn) can assume a hinged DNA structure (H-DNA) which is composed of triple-stranded and single-stranded regions. A model for the formation of H-DNA is proposed, based on two-dimensional gel electrophoretic analysis of DNA''s with different lengths of (TC .cntdot. AG)n copolymers. In this model, H-DNA formation is initiated at a small denaturation bubble in the interior of the copolymer, which allows the duplexes on either side to rotate slightly and to fold back, in order to make the first base triplet. This nucleation established which of several nonequivalent H-DNA conformations is to be assumed by any DNA molecule, thereby trapping each molecule in one of several metastable conformers that are not freely interconvertible. Subsequently, the acceptor region spools up single-stranded polypyrimidines as they are released by progressive denaturation of the donor region; both the spooling and the denaturation result in relaxation of negative supercoils in the rest of the DNA molecule. From the model, it can be predicted that the levels of supercoiling of the DNA determine which half of the (dT-dC)n repeat is to become the donated third strand.