Photochemical probe of DNA local structures

DNA是多态的，存在于各种不同的构象中。双链DNA可以采用多种序列依赖的二级结构，其范围从规范的右手B形式到左手Z形式。然而，由于每种结构的出现寿命都很短，并且很难建立一个系统来证明DNA的局部结构，因此与DNA不同结构构象相关的生物学作用还没有得到很好的理解。我们发现，将8-甲基-2'-脱氧鸟苷（m8G）和8-甲基鸟苷（m8rG）结合到DNA中，可以显著稳定Z形式，并促进B-Z过渡，即使对于含有at的序列也是如此。开发一种Z稳定单体单元，即Z稳定剂，使我们能够了解Z- dna的溶液结构，并揭示了在紫外线照射下，含有5-卤脲嘧啶的Z-形式产生Z-形式特异性2'α-羟基化的特异性2'β-氢抽象。我们还研究了5-卤脲嘧啶在a型、b型、g -四重奏和蛋白质诱导的DNA扭结中的光反应。由5-卤脲嘧啶在辐照下生成的2'-脱氧尿苷-5-基抽氢具有原子特异性，高度依赖于DNA结构。

DNA is polymorphic and exists in a variety of distinct conformations. Duplex DNA can adopt a variety of sequence-dependent secondary structures, which range from the canonical right-handed B form through to the left-handed Z form. However, the biological roles associated with the different structural conformations of DNA are not well understood because of the short lifetime of appearance of each structure and the difficulty in creating a system to demonstrate the DNA local structure. We found that incorporation of 8-methyl-2'-deoxyguanosine (m8G) and 8-methylguanosine (m8rG) into DNA dramatically stabilized the Z form, and facilitated the B-Z transition, even for AT-containing sequences. Developing a Z-stabilizing monomeric unit, the Z stabilizer, allowed us to understand the solution structure of Z-DNA and to reveal the specific 2'β-hydrogen abstraction that gives rise to the Z-form-specific 2'α-hydroxylation of the 5-halouracil-containing Z-form under UV irradiation. We also investigated the photoreaction of 5-halouracil in the A-form, B-form, G-quartet, and protein-induced DNA kinks. Hydrogen abstraction by 2'-deoxyuridin-5-yl generated from 5-halouracil under irradiation was atom specific and highly dependent on the DNA structure.