Ruthenium complex binding to DNA G-quadruplexes

2013年，科学家首次发现，被称为g -四重体的DNA“结”存在于人类细胞中。例如，一条单链DNA含有四组鸟嘌呤碱基，每组碱基的序列为ggg，它可以在钾离子的存在下折叠，从而形成相当稳定的结构。多年来，这一直是实验室的好奇，核酸爱好者对此感兴趣，但没有什么实际意义。一旦这些结构被证明是活细胞内在机制的一部分，这种情况就发生了惊人的变化。最著名的结构是在染色体末端发现的，它主要由大量的双螺旋DNA组成。在一端，有一个看起来像磨损的一端，一条由数百个重复的DNA序列组成的单链- gggtta -。在正常的衰老过程中，随着细胞不断分裂，这些磨损的末端变得越来越短，最终导致细胞死亡。然而，最近，据估计，人类基因组可能包含30万个可以形成g -四重体的区域。重要的是，其中一些现在被认为与基因的开启和关闭有关。癌症和其他基因疾病与基因的不适当转换有关，通常是基因损伤的结果。因此，人们对能够与这些结相互作用的小分子非常感兴趣，例如，识别它们，捕获它们，并将它们可视化。已知有数百种这样的分子，具有不同程度的特异性和结合强度。在雷丁，我们对一组钌化合物与DNA的结合进行了3D结构研究，这些化合物与所谓的“光开关”化合物有关，这种化合物的绰号来自于它与DNA结合时的发光（在黑暗中发光）特性，而不是在水中。有一大家族的化合物具有相关的性质，其中一些在照射下引起DNA损伤，因此可能用于肿瘤治疗。我们的工作显示了发光和DNA损伤的结构起源。在这项工作中，我们将开发具有g -四联体特异性识别特性的化合物。这些化合物根本不会与正常的双螺旋DNA结合，而只会识别“结”，理想情况下，是特定的“结”。我们有一些未发表的结果给了我们一些强有力的指示，包括一个晶体结构，显示了我们的一个新的钌配合物与g -四重体结合。我们的日本合作者使用我们的另一种新复合物，也有其他初步结果强烈地暗示了特异性。首先，生命系统中正常DNA的复制过程需要解开这些“结”。我们的一种化合物极大地阻碍了这种结解开过程，表明一种强而特异性的结合。其次，现在有可能买到一种抗体，它可以与整个细胞中的“结”特异性结合，但同样，抗体的结合模式尚不清楚。这是一种研究“结”如何参与细胞调节的不同方法，可用于研究健康细胞与癌细胞。这种化合物取代了抗体，再次表明了强而特异性的结合。

In 2013 it was shown for the first time that the DNA 'knot' known as the G-quadruplex was present in human cells. A single strand of DNA containing four runs of guanine bases with the sequence -GGG- in each, for example, can fold up in the presence of potassium ions to give a rather stable structure. For many years, this was a lab curiosity, of interest to nucleic acid enthusiasts but of little practical benefit. This situation changed strikingly once the structures were shown to be part of the intrinsic mechanism of the living cell. The best known structure is that found at the ends of chromosomes, which mainly consist of large amounts of double helical DNA. At one end, there is what looks like a frayed end, a single strand consisting of hundreds of repeats of the DNA sequence -GGGTTA-. In normal ageing these frayed ends become shorter and shorter as the cell repeatedly divides, leading to eventual cell death. More recently, though, it has been estimated that the human genome contains maybe 300,000 regions where a G-quadruplex could form. Importantly, some of these are now thought to be associated with the switching on and off of genes. Cancer and other diseases of the genes are associated with the inappropriate switching of genes, often as a result of genetic damage. Therefore there is great interest in small molecules which can interact specifically with these knots, to recognise them, to trap them, and to visualise them for example. Hundreds of such molecules are known, with varying degrees of specificity and binding strength.In Reading we have carried out 3D structural work on the binding to DNA of a group of ruthenium compounds related to the so-called 'light-switch' compound, which takes its nickname from is luminescence (glow-in-the-dark) property when bound to DNA but not in water. There is a large family of compounds with related properties, some causing DNA damage on irradiation and therefore of interest for possible tumour therapy. Our work has shown the structural origin of the luminescence and the DNA damage.In this work we will develop compounds showing specific recognition properties for G-quadruplexes. These compounds will not bind at all to normal double helical DNA but would just recognise the 'knot', and ideally, specific 'knots'. We have unpublished results which give us some strong pointers, including a crystal structure showing one of our new ruthenium complexes bound to a G-quadruplex. Our Japanese collaborators have other preliminary results strongly suggestive of specificity as well, using another of our new complexes. First, the copying process of normal DNA in living systems requires, among other things, the disentangling of these 'knots'. One of our compounds greatly hinders this knot-untying process, suggesting a strong and specific binding. Second, it is now possible to buy an antibody which binds specifically to the 'knots' in whole cells, but again, the binding mode of the antibody is not yet clear. This is a different way to study how the 'knots' are involved in cell regulation, and can be used to study healthy vs cancerous cells. This compound displaces the antibody, again suggesting strong and specific binding.