Maruyama A, Katoh M, Ishihara T, Akaike T
Department of Biomolecular Engineering, Tokyo Institute of Technology, Yokohama, Japan.
Bioconjug Chem. 1997 Jan-Feb;8(1):3-6. doi: 10.1021/bc960071g.
DNA triplex formation has been studied as a potential strategy for regulation of gene expression. The triplex is, however, unstable under physiological conditions, so that an effective stabilizer for the triplex formation is needed. Here is shown a novel strategy to stabilize the triplex based on the molecular design of a comb-type polycation. Linear polycations, such as poly(L-lysine) and poly(L-arginine), thermally stabilize DNA duplexes (and triplexes). The complexes between DNA and the polycation are irreversible and are liable to precipitate out of aqueous media. The irreversibility and phase separating properties of the complex impede association of single-stranded (ss) DNAs in the complex to form duplexes and triplexes. A comb-type polycation consisting of a poly(L-lysine) backbone and grafted chains of hydrophilic polymers was prepared. The comb-type copolymers increased solubility of their complex with DNA and suppressed conformational changes of DNA. Thermal melting curve analyses revealed that the comb-type copolymer markedly stabilized DNA triplexes and did not disturb ssDNAs in forming duplexes and triplexes. Reversible and one-step melting/reassociation transitions of poly(dA).2poly(dT) triplex were shown in the pressure of the copolymers. The stabilizing effect of the copolymer was larger than that of spermine, a polyamine considered effective in stabilizing triplexes. These results indicated that molecular design of polycations with a comb-type structure is a novel strategy to create efficient triplex stabilizers. Such comb-type copolymer consisting of various types of polycation backbones and hydrophilic graft chains may have many applications in which specific and precise interactions of polynucleotides are involved.
DNA三链体的形成已作为一种潜在的基因表达调控策略进行了研究。然而，三链体在生理条件下不稳定，因此需要一种有效的三链体形成稳定剂。本文展示了一种基于梳型聚阳离子分子设计来稳定三链体的新策略。线性聚阳离子，如聚（L-赖氨酸）和聚（L-精氨酸），可热稳定DNA双链体（和三链体）。DNA与聚阳离子之间的复合物是不可逆的，并且容易从水性介质中沉淀出来。复合物的不可逆性和相分离特性阻碍了复合物中单链（ss）DNA形成双链体和三链体。制备了一种由聚（L-赖氨酸）主链和亲水聚合物接枝链组成的梳型聚阳离子。梳型共聚物增加了其与DNA复合物的溶解度，并抑制了DNA的构象变化。热熔曲线分析表明，梳型共聚物显著稳定了DNA三链体，并且在形成双链体和三链体时不会干扰ssDNA。在共聚物存在下，聚（dA）·2聚（dT）三链体显示出可逆的一步解链/重新缔合转变。该共聚物的稳定作用大于精胺，精胺是一种被认为对稳定三链体有效的多胺。这些结果表明，具有梳型结构的聚阳离子的分子设计是创造高效三链体稳定剂的一种新策略。这种由各种类型的聚阳离子主链和亲水接枝链组成的梳型共聚物可能在涉及多核苷酸特异性和精确相互作用的许多应用中具有应用价值。
