Structures of RNA processing and Silencing Enzymes in Prokaryotes

描述(申请人提供)：像真核生物一样，细菌和古生菌已经进化出各种防御系统来保护自己免受自私的遗传因素(噬菌体、转座子和质粒)的伤害。另一方面，成功传播的可移动元件可以使细菌宿主受益，例如，通过引入抗药性基因。因此，了解防御系统不仅有助于深入了解原核生物的分子生物学原理，还可能为防御抗生素耐药性流行提供新的策略。最近，一种新的广泛的防御系统被发现，它的工作原理与以前所知的完全不同。聚集的规则间隔短回文重复序列(CRISPR)存在于40%的细菌和90%的古生菌基因组中，它们提供了一个基于小RNA的原核免疫系统。在这个非凡的过程中，捕捉过去感染记忆的DNA短序列被转录并处理成小RNA分子，然后与蛋白质一起形成模式，使新的入侵者核酸沉默。这项建议将研究目前发现的两种CRISPR机制的分子机制，一种是生产CRISPR RNA的机制，另一种是沉默入侵RNA的机制。实验目的是为了全面了解加工内切酶和RNA沉默复合体的结构和功能特性。相关性：细菌和古菌的CRISPR元素为通过交换和破坏遗传物质维持微生物环境的平衡提供了重要工具。CRISPR元件在医学上重要的细菌中发现，包括但不限于鼠疫耶尔森氏菌、结核杆菌、流感嗜血杆菌、幽门螺杆菌、脑膜炎奈瑟菌、创伤弧菌、金黄色葡萄球菌、伤寒沙门氏菌和破伤风杆菌。对CRISPR免疫的透彻理解对细菌病原体传播、抗菌素耐药性和宿主-病毒相互作用的研究具有重要意义。这一新途径的分子机制可能被用来建立对不良遗传因素的特异性免疫，例如那些传播抗生素耐药基因的基因。

DESCRIPTION (provided by applicant): Like eukarya, bacteria and archaea have evolved a variety of defense systems to protect themselves from selfish genetic elements (phages, transposons, and plasmids). On the other hand, successfully disseminated mobile elements can benefit the bacterial hosts, for instance, by introducing antibiotics resistant genes. Understanding the defense systems, therefore, not only offers insights on prokaryotic molecular biology principles but may also provide new strategies to defend the antibiotics resistance epidemics. Recently, a novel widespread defense system that functions on a completely different principle than those previously known was discovered. The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) are found in 40% of bacterial and 90% of archaeal genomes that confers a small RNA-based prokaryotic immunity system. In this remarkable process, DNA short sequences capturing the memories of past infection are transcribed and processed into small RNA molecules that then pattern with proteins to silence the new invader nucleic acids. This proposal will investigate the molecular mechanisms of two currently identified CRISPR machineries, that for production of the CRISPR RNAs and that for silencing invading RNA. Experimental aims are designed to provide a comprehensive understanding of the structural and functional properties of the processing endonuclease and the RNA silencing complex. Relevance: The CRISPR elements of bacteria and archaea provide an important vehicle for maintaining a balance in microbial environments through exchange and destruction of genetic materials. CRISPR elements are found in medically important bacteria that include but not limited to Yersinia pestis, Mycobacterium tuberculosis, Haemophilus influenzae, Helicobacter pylori, Neisseria meningitides, Vibrio vulnificus, Staphylococcus aureus, Salmonella Typhi and Clostridium tetani. A thorough understanding of the CRISPR immunity has important implications in studies of bacterial pathogen spread, antimicrobial resistance, and host-virus interactions. The proposed molecular mechanisms of this novel pathway may be exploited for building specific immunity against undesirable genetic elements such as those spreading antibiotics resistance genes.