BREX phage defence: expanding the role of cyclic nucleotide signalling in the prokaryotic immune system

“基因编辑”已经从科幻领域转移到主流生物技术领域。我们有能力编辑生物体的基因，以便操纵它们的外观、生长、行为和治愈疾病。这是通过“crispr-cas”实现的，这是一种经常在报纸上、甚至在流行的电视和流媒体节目中被查名的工具。人们不常提到的是，CRISPR-CAS是基于一场围绕着我们日常生活的古老而持续的战争的武器。地球上有真正数量惊人的细菌，它们的数量是被称为噬菌体的病毒的10：1。细菌和噬菌体已经共同进化了数百万年。谢天谢地，这些噬菌体不会伤害人类。但是，就像我们的免疫系统对感染做出反应一样，细菌被迫进化出保护系统免受噬菌体攻击的系统。这些防御系统通常有特定的活动，如切割DNA。因此，我们的许多生物技术都是从这些系统的应用中产生的，包括CRISPR-CASE。最近发现了细菌用于防御噬菌体的系统的爆炸性增长。因此，将我们自己的免疫系统与细菌的免疫系统进行比较的类比已经成为现实。现在已经证实，哺乳动物的抗病毒反应和细菌的噬菌体防御之间存在着进化和功能上的联系。此外，我们可以逆转这种关系，利用细菌中新系统的发现来预测和识别哺乳动物免疫系统中的新系统！这一发现表明，也许我们应该将细菌中的噬菌体防御视为一种“免疫系统”。因此，预计不同的防御系统将进行沟通并受到共同监管。鼓风机实验室的工作已经确定了共同调节不同防御系统的蛋白质。其他实验室的工作已经确定了一系列被称为环核苷酸的分子，它们在防御系统的组成部分之间移动，并打开或关闭它们。回到我们的类比，我们知道这些环核苷酸在人类中被用来控制免疫网络。因此，环核苷酸也可能是细菌免疫系统中控制的关键。我们已经确定了一种降解环核苷酸的防御蛋白，作为一种名为噬菌体排斥(Brex)的防御机制的一部分。目前还不清楚为什么会出现这种活动，以及它如何影响英国。英国退欧的整体机制也不清楚。我们的目标是在Brex的背景下研究环核苷酸的使用。我们将描述降解环核苷酸的蛋白质的活性，以及它更喜欢哪种形式的核苷酸。我们将研究组成Brex的各种蛋白质(有六种)是如何相互作用的，以及环核苷酸的存在可能如何改变这些相互作用。然后，我们将通过了解如何对Brex进行工程设计来对DNA进行修改，从而了解如何在生物技术上使用Brex。Brex增加了一种修饰，这对于控制DNA在衰老和疾病等过程中的使用非常重要。有针对性的修饰方法将为生物医学研究提供另一种工具。总体成果将是提供进一步的证据，证明细菌免疫系统具有凝聚力，并促进我们对Brex的理解，走向潜在的生物技术开发。

"Gene-editing" has transferred from the realms of sci-fi to mainstream biotechnology. We have the ability to edit the genes of organisms in order to manipulate how they look, grow, behave, and to cure disease. This has been made possible through "CRISPR-cas", a tool that now regularly gets name-checked in newspapers and even popular TV and streaming shows. What is not often mentioned is that CRISPR-cas is based upon the weaponry of an ancient and ongoing war that surrounds our everyday lives.The Earth is home to truly astronomical numbers of bacteria, and they are outnumbered 10-to-1 by viruses called bacteriophages. Bacteria and bacteriophages have been co-evolving for millions of years. These bacteriophages thankfully don't harm humans. But in the same way that our immune system responds to infections, bacteria have been forced to evolve systems that protect from bacteriophages. These defence systems often have specific activities, such as cutting DNA. As a result, many of our biotechnologies have arisen from the applications of these systems, including CRISPR-cas.There has been a recent explosion in the discovery of systems bacteria use for defence against bacteriophages. As a result, the analogy comparing our own immune system with that of bacteria has become reality. There are now proven evolutionary and functional links between the antiviral response in mammals and bacteriophage defence in bacteria. Furthermore, we can reverse this relationship, using the discovery of new systems in bacteria to predict forward and identify new systems in the mammalian immune system!This finding suggests that perhaps we should consider bacteriophage defence in bacteria as an "immune system". As such, the varied defence systems would be expected to communicate and be co-regulated. Work in the Blower lab has already identified proteins that co-regulate diverse defence systems. Work in other labs has identified a series of molecules called cyclic nucleotides that move between component parts of defence systems and switch them on or off. Going back to our analogy, we know that these cyclic nucleotides are used in humans to control networks of immunity. It follows that cyclic nucleotides might also therefore be key to control within the bacterial immune system.We have identified a defence protein that degrades cyclic nucleotides as part of a defence mechanism called Bacteriophage Exclusion (BREX). It is not currently understood why this activity is present, and how it impacts BREX. The overall mechanism for BREX is also not understood. Our objective is to investigate cyclic nucleotide usage in the context of BREX. We will characterise the activity of the protein that degrades cyclic nucleotides, and which forms of nucleotides it prefers to target. We will look at how the varied proteins that make up BREX (there are six), interact, and how the presence of cyclic nucleotides might alter these interactions. We will then look at how to use BREX biotechnologically by understanding how to engineer it to make modifications in DNA. BREX adds a modification that is important for controlling use of DNA in processes such as aging and disease. Having a targeted method of modification will provide another tool for biomedical research.The overall outputs will be to provide further evidence towards a cohesive bacterial immune system and progress our understanding of BREX towards potential biotechnological exploitation.