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首页> 外文期刊>Chemistry: A European journal >Structural Studies of LNA:RNA Duplexes by NMR: Conformations and Implications for RNase H Activity
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Structural Studies of LNA:RNA Duplexes by NMR: Conformations and Implications for RNase H Activity

机译：LNA：RNA双链体的核磁共振结构研究：RNase H活性的构象和含义。

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We have used NMR and CD spectroscopy to study the conforations of modified oligonucleotides (locked nucleic acid, LNA) containing a conformationally restricted nucleotide (T~L) with a 2'-O,4'-C-methylene bridge. We have investigated two LNA:RNA duplexes, d(CTGAT~(L)ATGC):r(GCAUAUCAG) and d(CT~(L)GAT~(L)AT~(L)GC):r(GCAUAUCAG), along with the ummodified DNA:RNA reference duplex. Increases in the melting temperatures of +9.6 deg C and + 8.1 deg C per modification relative to the numodified duplex were observed for these two LNA:RNA sequences. The three duplexes all adopt right-handed helix conformations and form normal Watson-Crick base pairs with all the bases in the anti conformation. Sugar conformations were determined from measurements of scalar coupling constants in the sugar rings and distance information derived from ~1H-~1H NOE measruements; all the sugars in the RNA strands of the three duplexes adopt an N-type conformatio n(A-type structure), whereas the sugars in the DNA strands change from an equilibrium between S-and N-type conformations in the ummodified duplex towards more of the N-type conformation when modified nucleotides are introduced. The presence of three modified T~L nucleotides induces drastic conformational shifts of the remaining ummodified nucleotides of the DNA strand, changing all the sugar conformations except those of the terminal sugars to the N type. The CD spectra of the three duplexes confirm the structural changes described above. On the basis of the results reported herein, we suggest that the observed conformational changes can be used to tune LNA:RNA duplexes into substrates for RNase H:Partly modified LNA:RNA duplexes may adopt a duplex structure between the standard A and B types, thereby making the RNA strand amenable to RNase H-mediated degradation.
机译：我们已使用NMR和CD光谱研究了修饰的寡核苷酸（锁核酸，LNA）的构象，所述寡核苷酸包含具有2'-O，4'-C-亚甲基桥的构象受限的核苷酸（T〜L）。我们研究了两个LNA：RNA双链体，d（CTGAT〜（L）ATGC）：r（GCAUAUCAG）和d（CT〜（L）GAT〜（L）AT〜（L）GC）：r（GCAUAUCAG）经修饰的DNA：RNA参考双链体。对于这两个LNA：RNA序列，相对于未修饰的双链体，每个修饰的解链温度升高了+ 9.6℃和+ 8.1℃。三个双链体均采用右旋螺旋构象，并与所有反构象的碱基形成正常的Watson-Crick碱基对。糖的构象是根据糖环中标量偶合常数的测量值以及从〜1H-〜1H NOE测量得出的距离信息确定的;三个双链体的RNA链中的所有糖均采用N型构象n（A型结构），而DNA链中的糖从未修饰双链体的S和N型构象之间的平衡变为更多当引入修饰的核苷酸时，N型构象的变化。三个修饰的T〜L核苷酸的存在引起DNA链剩余的未修饰的核苷酸的剧烈构象转变，将除末端糖之外的所有糖构象改变为N型。三个双链体的CD光谱证实了上述结构变化。根据此处报告的结果，我们建议观察到的构象变化可用于将LNA：RNA双链体调节为RNase H的底物：部分修饰的LNA：RNA双链体可在标准A和B类型之间采用双链体结构，从而使RNA链适合RNase H介导的降解。

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