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佛罗里达州立大学李红教授、南京大学于涵洋教授7月10日学术报告
作者: 佚名 -- 发布时间:2017/7/7

时间:2017-7-10(周一),10:00-12:00am

地点:生命科学学院B215

主持人:黄震教授

1、  主讲人:李红教授(佛罗里达州立大学)

报告题目:Characterization of a new CRISPR-Cas9 specific for cytosine-adjascent DNA

主要科学成就:

Endoribonucleases

Endoribonucleases recognize and cleave functional RNA. The structural diversity in RNA, which results in a range of folds, presents a challenge for endoribonucleases to seek out and excise specific phosphodiester bonds. We have characterized in depth the biochemical and structural properties of two families of metal-independent endoribonucleases: 1) the intron splicing endoribonuclease (Science, 2006, 312:906; Nature, 2006, 441:375; PNAS, 2005, 102:17934l; NAR, 35(12):4001-4006); and 2) the CRISPR-Cas RNA processing endoribonuclease (Genes & Dev., 2008, 22:3489; Structure, 2011, 19:257; Structure, 2013, 21(3):385-93 Structure, 2016, 24(4):547-54.). We discover from studying a wide range of endoribonuclease-RNA complexes that, regardless of the foldability of RNA, endoribonucleases are capable of driving RNA to the required inline conformation at the site of cleavage for catalysis (Curr. Opin. Stru. Bio, 2007, 17:293; Cellular and Mol. Life Sciences, 2008, 65:1176; Structure, 2014, 23(1):13-20.).

RNA-guided enzymes

RNA-guided enzymes are uniquely suited to target nucleic acid substrates due to the combined programmability of the RNA and the catalytic power of proteins. We have and continue to work on molecular mechanisms of two families of RNA-guided enzymes: 1) the RNA-guided modification enzymes required for ribosome biogenesis (Nature Struc. and Mol. Bio., 2003, 10:256; Mol. Cell, 2006, 21:249; Nature Struc. and Mol. Biol., 2007, 14:1189; Nature Struc. and Mol. Bio. 2009, 16:740; Mol. Cell, 2010, 39:939) and their maturation processes driven by ATP-dependent chaperones; 2) the RNA-guided DNA/RNA degradation enzymes involved in bacterial CRISPR-Cas immunity (Cell Reports, 2014, 9(5):1610-7; Genes & Develop., 2014, 28(21):2432-43; Mol. Cell, 2013, 52(1):146-52; NAR, 2014, 42(2):1129-38) and their application in genome-editing (ACS Synthetic Biology, 2017, Mar. 20; Patent pending).

2、  主讲人:于涵洋教授2015 年第十一批千人计划青年人才),

报告题目:In vitro Selection of Functional Xeno-Nucleic Acids (XNAs)

研究方向:核酸化学生物学,以体外筛选技术鉴定功能性核酸分子

报告摘要:Aptamers are single-stranded nucleic acid molecules that could fold into distinct tertiary structures with specific binding capacities to various targets ranging from metal ions to proteins. Due to the ease in production and modification, aptamers hold great promise in applications such as biosensing and theranostics. However, natural nucleic acid aptamer-based affinity molecules suffer from nuclease-mediated degradation in biological environment. While this instability issue could be partially alleviated by introducing chemical modifications to the nucleic acid backbone after aptamer identification, such alterations often cause undesired consequences including reduced affinity or even complete loss of function.

To solve this problem, we applied the technique of in vitro selection directly to a type of XNA, namely TNA (threose nucleic acid), which contains an unnatural backbone and is inherently nuclease-resistant. We first chemically synthesized four monomer building blocks (TNA triphosphates, tNTPs) for polymer synthesis, and screened a number of enzymes for polymerase activity which recognizes TNA as substrate. Having found such “TNA polymerase” and “TNA reverse transcriptase”, we successfully isolated TNA aptamers that bind specifically to human thrombin with nanomolar affinity. Additionally, we demonstrated that TNA molecules exhibited superior resistance to nucleases and remained intact in human serum even after days. 


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