Donlan M E, Lu P
University of Pennsylvania, Department of Chemistry, Philadelphia 19104.
Nucleic Acids Res. 1992 Feb 11;20(3):525-32. doi: 10.1093/nar/20.3.525.
A dynamic heterogeneity which correlates with the function of the operator DNA in the lactose operon of E. coli. was previously observed (1) as a local minimum in the thymine imino proton T1 centered at a GTG/C-CAC sequence. Since this triplet occurs frequently in DNA regulatory regions, it was proposed that these sequences may be part of a structural element for specific protein interaction. We examine here three additional biologically significant 17 base pair duplexes containing GTG/CAC triplets: (1) a sequence from the mouse heavy chain immunoglobulin enhancer, (2) a sequence from the critical core of the Simian Virus 40 (SV40) enhancer, and (3) a sequence from pBR322 plasmid used as control for experiments with the SV40 DNA sequences. The 1H NMR resonance assignment for nearly all the nonexchangeable protons for both eukaryotic enhancer duplexes with the exception of the H5'/H5" protons was accomplished to use for structural analysis of these duplexes. The data presented show several NOE's associated with the GTG/CAC triplets which suggest structural variation from uniform B-DNA. In addition, anomalous broad crosspeaks for the fixed thymine methyl to its own H6 proton in combination with the imino proton kinetics associated with these triplets reinforces the original observation of a sequence dependent dynamic variation.
先前观察到一种与大肠杆菌乳糖操纵子中操纵基因DNA功能相关的动态异质性(1)，其表现为以GTG/C-CAC序列为中心的胸腺嘧啶亚氨基质子T1处的局部最小值。由于这种三联体在DNA调控区域中频繁出现，因此有人提出这些序列可能是特定蛋白质相互作用的结构元件的一部分。我们在此研究另外三个含有GTG/CAC三联体的具有生物学意义的17碱基对双链体：(1)来自小鼠重链免疫球蛋白增强子的序列，(2)来自猿猴病毒40(SV40)增强子关键核心的序列，以及(3)来自pBR322质粒的序列，用作SV40 DNA序列实验的对照。除H5'/H5"质子外，完成了几乎所有真核增强子双链体不可交换质子的1H NMR共振归属，以用于这些双链体的结构分析。所呈现的数据显示了几个与GTG/CAC三联体相关的核Overhauser效应(NOE)，这表明其结构不同于均匀的B-DNA。此外，固定胸腺嘧啶甲基与其自身H6质子之间异常宽的交叉峰，结合与这些三联体相关的亚氨基质子动力学，强化了最初观察到的序列依赖性动态变化。
