Thomas T J, Ashley C, Thomas T, Shirahata A, Sigal L H, Lee J S
Department of Medicine, University of Medicine and Dentistry of New Jersey Robert Wood Johnson Medical School, New Brunswick 08903, USA.
Biochem Cell Biol. 1997;75(3):207-15.
The formation and stability of triplex DNA were investigated in the presence of a number of tetramine (+4) and pentamine (+5) derivatives of spermine with altered spacing between the positive charges and bis(ethyl) substitution of pendant amino groups. Thermal denaturation profiles were measured for the duplex and triplex forms of poly[d(TC)].poly[d(GA)] and poly(dA).poly(dT); in both cases the pentamines were more effective than the tetramines in increasing the melting temperature (Tm) of the triplexes. Some structural effects were evident, although bisethylation of the polyamines had only a minor effect on the Tm of pyrimidine-purine-pyrimidine triplexes. Relative association constants to poly(dT).poly(dA).poly(dT) and poly[d(AT)] were measured by an ethidium competition assay. These results demonstrated tighter binding of the pentamines by a factor of up to 10-fold, but bisethylation consistently decreased the relative association constants to the triplex. A third assay involving transmolecular triplex formation between separated pyrimidine-purine tracts in plasmid DNA was also employed. Again the pentamines promoted triplex formation at lower concentrations than the tetramines but structural effects were very important in determining the degree of triplex formation. These results may be important for the design of suitable ligands to stabilize triplex DNA in antigene therapeutics and to elucidate the mechanism of action of polyamine analogues as antitumor drugs.
在存在多种精胺的四胺（+4）和五胺（+5）衍生物的情况下，研究了三链DNA的形成和稳定性，这些衍生物的正电荷之间的间距发生了改变，且侧链氨基进行了双（乙基）取代。测量了聚[d(TC)]·聚[d(GA)]和聚(dA)·聚(dT)的双链和三链形式的热变性曲线；在这两种情况下，五胺在提高三链体的解链温度（Tm）方面比四胺更有效。一些结构效应很明显，尽管多胺的双乙基化对嘧啶-嘌呤-嘧啶三链体的Tm只有轻微影响。通过溴化乙锭竞争试验测量了与聚(dT)·聚(dA)·聚(dT)和聚[d(AT)]的相对缔合常数。这些结果表明五胺的结合更紧密，高达10倍，但双乙基化始终降低了与三链体的相对缔合常数。还采用了第三种试验，涉及质粒DNA中分离的嘧啶-嘌呤片段之间的分子间三链体形成。同样，五胺在比四胺更低的浓度下促进三链体形成，但结构效应在决定三链体形成程度方面非常重要。这些结果对于设计合适的配体以在反基因治疗中稳定三链DNA以及阐明多胺类似物作为抗肿瘤药物的作用机制可能很重要。
