Structures of RNA processing and Silencing Enzymes in Prokaryotes

描述（由申请人提供）：像真核生物一样，细菌和古细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子（噬菌体、转座子和质粒）的侵害。另一方面，成功传播的移动元素可以使细菌宿主受益，例如，通过引入抗生素抗性基因。因此，了解这些防御系统不仅可以提供对原核分子生物学原理的见解，而且可能为防御抗生素耐药性流行病提供新的策略。最近，人们发现了一种新的、广泛存在的防御系统，它的运作原理与以前已知的完全不同。集群规则间隔短回文重复序列（crispr）存在于40%的细菌和90%的古细菌基因组中，这赋予了一个基于小rna的原核免疫系统。在这个非凡的过程中，捕获过去感染记忆的DNA短序列被转录并加工成小RNA分子，然后与蛋白质形成模式，以沉默新的入侵核酸。本提案将研究目前鉴定的两种CRISPR机制的分子机制，一种用于产生CRISPR RNA，另一种用于沉默入侵RNA。实验目的是提供一个全面的结构和功能特性的理解加工内切酶和RNA沉默复合体。相关性：细菌和古细菌的CRISPR元件通过交换和破坏遗传物质，为维持微生物环境的平衡提供了重要的载体。CRISPR元件存在于医学上重要的细菌中，包括但不限于鼠疫耶尔森菌、结核分枝杆菌、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梭菌。深入了解CRISPR免疫对细菌病原体传播、抗微生物药物耐药性和宿主-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于建立针对不良遗传因子（如传播抗生素抗性基因）的特异性免疫。

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.