Molecular Mechanisms of Sigma Factor Inhibition in a Gene Expression Switch

我们打算研究细胞如何通过激活“基因表达开关”来彻底改变自己的身份。这样的转变对于自然保持健康很重要，例如在胚胎发育中，胚胎发育始于相同的细胞，然后至关重要地转变为组成发育的人类的不同类型的细胞。相反，当细胞癌变或病原体入侵宿主时，这些转化会造成伤害。基因表达开关涉及一种独特的遗传指令失活程序，并被一种导致细胞性质根本性转变的替代方案所取代。在这项研究中，我的团队将研究细菌孢子形成中的一种特殊的基因表达开关事件，这是“医院超级细菌”持续存在的部分原因，因为孢子是一种长寿的细菌形式，对清洁剂具有抵抗力，在缺乏天然肠道微生物群的患者中茁壮成长。在基因表达开关中，有特定的蛋白质在高度调控的过程中编排遗传指令。我们打算使用间接技术来揭示其中一些蛋白质的详细分子形状，因为它们太小了，即使使用强大的显微镜也看不到。我们专门测量蛋白质的形状和它们结合的方式，通过人工大量生产它们，并在细菌的帮助下作为我们的“蛋白质工厂”。然后，我们通过处理它们的行为来推断蛋白质的分子结构，当我们从它们身上反射X射线或将它们置于强磁场中时。每种技术都有其优缺点，但我们的组合方法可以产生补充信息，填补仅使用其中一种方法留下的空白。与微生物学家合作，我们将向彼此的实验提供信息，以建立细菌孢子形成中这种基因表达开关的机制图。例如，如果我们在我们的一种蛋白质中发现了一种突变，使其与其伴侣更紧密地结合在一起，我们的合作者可以在细菌内进行同样的突变，以测试它在生命系统中是否具有预期的效果。通过解决这个拼图，我们希望能够更好地设计新的抗生素，以应对日益严重的细菌耐药性问题，该项目还对理解健康和疾病各个方面的基因表达开关具有更长期的意义。

We propose to study the way cells can completely transform their identity by activating a 'gene expression switch'. Such transformations are important to naturally maintain health e.g. in embryo development which begins with identical cells which then crucially change into the different types of cells that make up a developed human. Conversely, these transformations can cause harm e.g. when cells become cancerous or pathogens invade hosts. A gene expression switch involves a distinct programme of genetic instruction being deactivated and replaced with an alternative that leads to radical transformation of the cell's nature.In this study my group will examine a particular gene expression switch event in bacterial spore formation which is partially responsible for the persistence of 'hospital superbugs' as spores are a long-lived bacterial form, resistant to cleaning agents and thriving in patients depleted of natural gut microflora.In a gene expression switch there are specific proteins that choreograph genetic instruction in a highly regulated process. We intend to uncover the detailed molecular shapes of some of these proteins using indirect techniques as they are too small to see even using powerful microscopes. We specialise in measuring protein shapes and the way they fit together by producing them artificially in large quantities, with the help of bacteria which act as our 'protein factories'. We then deduce the proteins' molecular structures by processing their behaviour when we bounce X-rays off them or put them in strong magnetic fields. Each of these techniques has its strengths and weaknesses but our combined approach can yield complementary information filling in the gaps left by using just one of the methods. Collaborating with a microbiologist we will feed information into each others' experiments to build up a mechanistic picture of this gene expression switch in bacterial spore formation. For example, if we identify a mutation in one of our proteins that makes it bind more tightly to its partner our collaborator can make the same mutation within bacteria to test whether it has the predicted effect in living systems.By solving this jigsaw puzzle we hope to be in a stronger position to design novel antibiotics to attack the increasing problem of bacterial drug resistance and the project also has longer term implications for understanding gene expression switches in all aspects of health and disease.