脱氧核酶（DNAzymes）高效催化降解新冠病毒RNA的研究

我们计划设计和改造脱氧核酶（DNAzyme）来特异性识别并剪切新冠病毒RNA。DNAzyme与其它基因沉默酶切技术相比（如核酶），具有分子相对小、易于设计和修饰、稳定性高、合成成本低等诸多优势。其中，能够剪切RNA的8-17 DNAzyme（Dz8-17）在基因沉默上有巨大的前景。不幸的是, 它对二价金属离子高度依赖。由于细胞内游离态二价金属离子浓度低，因此导致DNAzyme在细胞内活性低，这极大地阻碍了它在基因沉默领域的应用。尽管科学家们努力尝试各种办法来改善DNAzyme细胞内的活性，但收效甚微。摆脱Dz8-17对二价金属离子的依赖性，提高它的细胞内活性已成为一大难题。基于前期我们对Dz8-17的晶体结构解析，本项目将对Dz8-17分子结构和功能进行改造，引入有机阳离子，摆脱它对二价金属离子的依赖，从而提高Dz8-17在细胞内的催化活性，以便达到特异性降解新冠病毒RNA的目的。

We plan to design and reconstruct DNAzyme for specifically cleaving COVID-19 RNA. Compared with other enzymatic gene-silencing technologies (such as ribozymes), DNAzyme has several advantages, including smaller molecular weight, relatively stable in serum, easy to design and modify, and low cost to synthesis, which makes DNAzyme a promising tool in the field of gene silencing. Among them, the RNA-cleaving DNAzyme (Dz8-17) has great potential in gene silencing field. Unfortunately, Dz8-17 is highly dependent on divalent metal ions. Since the concentration of intracellular free-divalent-metal ions is low, Dz8-17 has low intracellular activity, which hinders the application of DNAzyme in the field of gene silencing. Although scientists have tried various ways to improve its intracellular activity, achieving high activity of DNAzyme in cells has become a challenge worldwide. Based on our crystal structure of Dz8-17, we plan to modify the molecular structure of Dz8-17 in order to improve the catalytic activity of DNAzyme inside and outside cells in the absence of divalent metal ions. Eventually, we will achieve RNA-specific degradation and COVID-19 RNA cleavage with the DNAzyme in vivo. The success on this project will transform the field of gene silencing and allow DNAzymes to be widely used in functional genomics and therapeutic discovery in the future.