The differential role of PU.1 in normal and malignant haematopoiesis: from master regulator of differentiation to coordinator of leukaemia networks

细胞的行为是由它们所含的蛋白质决定的。这种蛋白质组成在细胞类型之间，甚至在组织内的细胞之间存在很大差异，并解释了我们观察到的不同细胞行为和功能。这些蛋白质的水平以及为什么不同的蛋白质存在于特定的细胞中是由严格调控的过程决定的，称为转录，其中称为转录物的中间产物是从基因的DNA模板产生的，以及翻译，其中转录物然后用于组装由该基因编码的特定蛋白质。转录过程在血液形成中已经得到了很好的研究。血液是一种非常复杂的组织，包含不同的携带氧气的专门细胞，导致血液凝结的细胞和抵抗感染的细胞。然而，血液中的每一个细胞都是由一个来源产生的：造血干细胞（HSC），不同的细胞通过一个称为分化的有序过程成熟并变得更加专业化。一般来说，分化是由称为转录因子的专门蛋白质精心策划的，这些转录因子结合并调节特定基因的DNA，其蛋白质产物是专门化所必需的。然后，转录因子的结合指导从该基因产生转录本，导致蛋白质表达。这些转录因子的表达也受到严格控制，并通过分化和特化而发生变化。白血病和大多数癌症的主要特征之一是这种有序的分化过程被阻断，实际上，没有特化的成熟血细胞形成。急性白血病，如急性髓性白血病（AML），是具有令人沮丧的存活率的侵袭性癌症，因此是未满足的医疗需求。我们最近发现，通常与正常血液分化相关的称为PU.1的转录因子也是维持AML（一种缺乏分化的细胞状态）所必需的。该项目将专注于回答为什么PU.1驱动正常细胞分化但维持AML的有趣问题。乍一看，这似乎是违反直觉的，但我们推测：1）PU.1蛋白水平的差异，2）其与不同靶基因的结合和调节的差异，以及3）与正常和白血病状态之间相互作用的蛋白质的差异及其结构的改变（称为翻译后修饰）解释了这种改变的行为。我们将在本提案中询问这些途径，在相关模型系统和多个AML患者样本中利用最先进的技术。此外，我们将用特定的药物和遗传扰动靶向PU.1及其相互作用伙伴，以确定它是否可能是AML患者的相关和安全的治疗靶点。因此，该项目的可能结果是，我们将显着提高我们对白血病生物学和血细胞正常分化的理解，我们将确定PU.1及其相互作用蛋白作为AML的潜在治疗靶点，并且我们可能建议这种侵袭性疾病的有效治疗。

The behaviour of cells is determined by the proteins that they contain. This protein composition greatly differs between cell types and even between cells within tissues and explains the different cell behaviours and functions that we observe. The levels of these proteins and why different proteins are present in specific cells are determined by tightly-regulated processes called transcription, where an intermediate product called a transcript is generated from a gene's DNA-template, and translation, where the transcript is then used to assemble the specific protein coded for by that gene. The process of transcription has been well studied in blood formation. Blood is a very complex tissue, containing different specialised cells that carry oxygen, cells that cause the blood to clot and cells that fight infection. However, every cell within the blood is generated from a single source: the haematopoietic stem cell (HSC), with the differing cells maturing and becoming more specialised through an ordered process called differentiation. In general, differentiation is orchestrated by specialised proteins called transcription factors that bind to and regulate the DNA of specific genes whose protein products are necessary for specialisation. The binding of the transcription factors then instruct the generation of transcripts from that gene, resulting in protein expression. The expression of these transcription factors is also tightly controlled and changes through differentiation and specialisation.One of the cardinal features of leukaemias, and most cancers, is that this ordered process of differentiation is blocked and in effect, no specialised mature blood cells are formed. Acute leukaemias, such as Acute Myeloid Leukaemia (AML), are aggressive cancers with a dismal survival rate and are thus an unmet medical need. We have recently discovered that a transcription factor called PU.1 that is usually associated with normal blood differentiation is also absolutely required to maintain AML, a cellular state that lacks differentiation. This project will focus on answering the interesting question of why PU.1 drives differentiation in normal cells yet maintains AML. This seems at first-glance counterintuitive, however we speculate that: 1) differences in levels of the PU.1 protein, 2) differences in its binding to and regulation of different target genes and 3) differences in the proteins that it interacts with and alterations in its structure (called post-translational modifications) between the normal and leukaemia state explain this altered behaviour. We will interrogate these avenues in this proposal, utilising state-of-the-art techniques in relevant model systems and multiple AML patient samples. Moreover, we will target PU.1 and its interaction partners with specific drugs and genetic perturbations to determine if it may be a relevant and safe therapeutic target in patients with AML. Therefore, the likely outcomes of this project are that we will significantly improve our understanding both of leukaemia biology and of the normal differentiation of blood cells, that we will identify PU.1 and its interacting proteins as potential therapeutic targets in AML and potentially that we may suggest an effective therapy in this aggressive disease.