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组织内细胞之间都有很大差异，这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不同蛋白质在特定细胞中出现的原因是由严格调控的转录过程决定的，转录过程中，基因的dna模板产生一种称为转录本的中间产物，然后翻译，转录本随后被用来组装由该基因编码的特定蛋白质。转录过程在血液形成过程中得到了很好的研究。血液是一种非常复杂的组织，包括携带氧气的不同细胞、导致血液凝固的细胞和对抗感染的细胞。然而，血液中的每个细胞都是由单一来源产生的：造血干细胞（HSC），不同的细胞通过一个被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特殊蛋白质精心安排的，转录因子结合并调节特定基因的DNA，其蛋白质产物是特化所必需的。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，没有形成专门的成熟血细胞。急性白血病，如急性髓性白血病（AML），是侵袭性癌症，生存率低，因此是一个未满足的医疗需求。我们最近发现，一种称为PU.1的转录因子通常与正常血液分化有关，它也是维持AML（一种缺乏分化的细胞状态）所绝对需要的。该项目将专注于回答一个有趣的问题，即为什么PU.1在正常细胞中驱动分化，但仍维持AML。乍一看，这似乎是违反直觉的，然而我们推测：1)PU.1蛋白水平的差异，2)它与不同靶基因的结合和调节的差异，3)它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。在本提案中，我们将在相关模型系统和多个AML患者样本中利用最先进的技术来研究这些途径。此外，我们将针对PU.1及其与特定药物和遗传扰动的相互作用伙伴，以确定它是否可能是AML患者相关且安全的治疗靶点。因此，该项目可能的结果是，我们将显著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，并可能为这种侵袭性疾病提供有效治疗。

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.