Rao K E, Gosselin G, Mrani D, Périgaud C, Imbach J L, Bailly C, Hénichart J P, Colson P, Houssier C, Lown J W
Université de Montpellier II, Sciences et Techniques du Languedoc, Laboratoire de Chimie Bio-Organique, URA CNRS, France.
Anticancer Drug Des. 1994 Jun;9(3):221-37.
The properties of certain hybrids 3 and 5 bearing a photoactivatable psoralen group attached to DNA sequence recognizing lexitropsin carriers have been examined. The hybrids bind to poly(dA-dT) with Kapp of 2.8 and 0.9 x 10(7) M-1, i.e. greater than or equal to that of netropsin (Kapp = 1.0 x 10(7) M-1), indicating that the psoralen moiety may contribute to binding in the case of 5. Photoinduced cross-linking of DNA by 3 and 5, while efficient, is less so than that of individual psoralens and reaches a maximum at a ligand to DNA base pair ratio (r) of 0.2. Complementary strand methidium-propyl-EDTA (MPE).Fe(II) footprinting demonstrated that, in the dark, the sequence preferential recognition of hybrids 3 and 5 is dominated by the lexitropsin moiety. Examination of 360 nm photoinduced DNA cross-linking by the hybrids 3 and 5 was carried out using an exonuclease III stop assay. This revealed that > 95% of the DNA remained double stranded, indicating that 3 and 5 generate primarily biadducts at AT-rich sequences. This assay also located individual monoadduct sites, some of which are remote from the dominant cross-linked sites. When the samples were exposed to 254 nm UV light before loading onto the gel to reverse the photoproducts, the pattern of the exonuclease III stop bands was not altered significantly compared with the experiment without 254 nm irradiation. It is concluded that these termination sites include both mono- and biadducts. Electric linear dichroism examination of the DNA complexes of hybrids 3 and 5 (without light activation) provides evidence that the lexitropsin portion binds in the minor groove, while the psoralen portion intercalates in a suitably located site for subsequent photoinduced cross-linking.
已对某些带有与识别DNA序列的lexitropsin载体相连的光活化补骨脂素基团的杂合物3和5的性质进行了研究。这些杂合物与聚（dA-dT）结合，其表观解离常数（Kapp）分别为2.8和0.9×10⁷ M⁻¹，即大于或等于纺锤菌素（Kapp = 1.0×10⁷ M⁻¹），这表明在杂合物5的情况下补骨脂素部分可能有助于结合。杂合物3和5对DNA的光诱导交联虽然有效，但比单个补骨脂素的交联效率低，并且在配体与DNA碱基对的比例（r）为0.2时达到最大值。互补链甲基丙基乙二胺四乙酸（MPE）.Fe（II）足迹法表明，在黑暗中，杂合物3和5对序列的优先识别主要由lexitropsin部分主导。使用核酸外切酶III终止分析法对杂合物3和5在360 nm光诱导下的DNA交联进行了研究。结果显示，> 95%的DNA保持双链状态，这表明杂合物3和5主要在富含AT的序列处产生双加合物。该分析还确定了单个单加合物位点，其中一些位点远离主要的交联位点。当样品在加载到凝胶之前暴露于254 nm紫外光以逆转光产物时，与未进行254 nm照射的实验相比，核酸外切酶III终止带的模式没有明显改变。由此得出结论，这些终止位点包括单加合物和双加合物。对杂合物3和5的DNA复合物（无光激活）进行的电线性二色性检查提供了证据，表明lexitropsin部分结合在小沟中，而补骨脂素部分插入到一个合适的位置以便随后进行光诱导交联。
