The CMR complex for prokaryotic RNA silencing

病毒和细胞之间的战斗是残酷的，经常被比作“军备竞赛”。这是最古老的战争--与生命本身一样古老。病毒感染每年在全球造成数百万人伤亡。病毒对细胞施加的极端进化压力，反之亦然，一直是并仍然是进化的关键驱动力。对于人类来说，有明确的当务之急是探索病毒介导的细胞杀死病原体的可能性，反过来，利用自然界中的细菌病毒免疫系统来造福于食品生产。可以说，在过去的5-10年里，原核生物分子生物学中最令人兴奋的发现是CRISPR系统。CRISPR是在许多细菌和古菌的基因组中发现的DNA序列。它们由位于“间隔区”两侧的短重复序列组成，这些间隔区通常来自病毒序列。基因组的CRISPR区域被转录成RNA拷贝，然后被切碎以产生单独的CRISPR RNA分子，每个分子都有可能与入侵病毒的序列相匹配。CRISPR介导的病毒防御(或干扰)由两个大型、复杂的分子机器CASCADE和CMR介导，分别以病毒DNA和RNA为靶标。这个项目的重点是CMR建筑群，人们对它的了解较少。我们已经证明，CMR在序列特异性反应中使用CRISPR RNA来降解病毒RNA靶标。我们现在希望了解这个反应的分子基础，这可能是原核生物中独一无二的。研究将集中在降解RNA的酶的活性部位以及RNA和蛋白质之间相互作用的细节上。此外，我们的目标是利用CMR复合体在原核生物中发展序列依赖的RNA沉默。这项技术不适用于原核生物，不像真核生物那样，在真核生物中使用RNAi系统来沉默特定的基因。如果我们能够开发这项技术，它将为操纵细菌和古菌中的基因表达打开新的可能性之门，并有许多下游应用。

The battle between viruses and cells is brutal and often compared to an "Arms Race". It is the most ancient of wars - as old as life itself. Viral infections cause millions of human casualties globally every year. The extreme evolutionary pressure exerted on cells by viruses, and vice versa, has been and remains a key driving force in evolution. For humankind, there are clear imperatives to explore the possibilities of virus-mediated cell killing for pathogenic bacteria and, conversely, to harness bacterial virus immunity systems in nature to the benefit of food production. Arguably, most exciting discovery in prokaryotic molecular biology in the past 5-10 years is the CRISPR system. CRISPRs are DNA sequences found in the genomes of many bacteria and archaea. They consist of short repeats flanking "spacers" that are often derived from viral sequences. The CRISPR region of the genome is transcribed to make an RNA copy, which is then chopped up to generate individual CRISPR RNA molecules, each with the potential to match the sequence of an invading virus. CRISPR-mediated viral defence (or Interference) is mediated by two large, complex molecular machines, CASCADE and CMR, targetting viral DNA and RNA, respectively. This project is focused on the CMR complex, which is less well understood. We have shown that CMR uses CRISPR RNA to degrade viral RNA targets in a sequence specific reaction. We now wish to understand the molecular basis for this reaction, which is probably unique in prokaryotes. Studies will focus on the active sites of the enzyme that degrades the RNA and the details of the interactions between RNA and protein. Further, we aim to harness the CMR complex to develop sequence dependent RNA silencing in prokaryotes. This technology is not available in a robust form for prokaryotes, unlike in eukaryotes where the RNAi system is used to silence specific genes. If we can develop this technology it will open the door to new possibilities in the manipulation of gene expression in bacteria and archaea with many downstream applications.