Investigating regulation and function of the cytosine deaminase APOBEC3A during cell cycle re-entry

研究细胞周期再进入过程中胞嘧啶脱氨酶 APOBEC3A 的调节和功能

• 批准号: BB/V010271/2
• 负责人: Tim Fenton
• 金额: $ 64.06万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FV010271%2F2
• 关键词: Investigating; regulation; function; cytosine; deaminase

One way in which our bodies fight viral infections is to attack viral genomes (either DNA or RNA, depending on the virus) when viruses enter our cells and attempt to replicate. One protein involved in this immune response, APOBEC3A (A3A) modifies cytosine, one of the four building blocks of DNA and RNA, causing errors (mutations) and breaks in viral genes. A3A is not normally found at high levels in our cells except in certain specialised immune cells called macrophages. It is switched on in response to infection and plays an important role in protecting us from a range of viruses, however it is also activated in inflammatory conditions including eczema and psoriasis. Although A3A helps to defend us from viral infections, this protection comes at a cost, as we and others have shown that it can turn against our own genes, generating mutations that cause cancer. Numerous studies have confirmed that this process occurs in a large proportion of cancers, particularly those arising in the tissues (epithelia) that line the mouth and throat, lung, breast, bladder and cervix. Not only does A3A mutate our DNA during cancer development but it appears that A3A can continue to act in this rogue fashion while patients are receiving chemotherapy; driving drug-resistance and ultimately, treatment failure. This knowledge has stimulated initiatives in academia and industry to develop A3A inhibitors; drugs that could block this mutagenic activity in patients receiving chemotherapy, thereby preventing tumours from becoming resistant to the therapy. While this approach holds the potential to improve outcomes for millions of cancer patients, there is much we do not yet know about the way in which A3A is controlled and about the functions that it performs in the normal, healthy epithelial cells from which A3A-mutated cancers develop. Without this knowledge, we have little idea of what triggers rogue A3A activity, or what the side-effects of inhibiting A3A activity might be in patients. In this proposal, we set out a series of experiments to address these questions, based on three key findings that we have made from studying A3A in cultured human epithelial cells. 1) We have discovered that by mimicking a wound-healing response in epithelial cells, we can switch the A3A gene on to levels far higher than those previously seen in these cells and that remains at very high levels as these cells replicate their DNA, a time at which the DNA is potentially vulnerable to rogue A3A activity. 2) By deleting the A3A gene in epithelial cells, we have uncovered a previously unknown role for A3A in regulating the rate at which these cells divide, a role that is critical to understand if we are to anticipate the effects of targeting A3A for cancer therapy. 3) Recent studies have demonstrated that A3A can modify many cellular messenger RNAs, the intermediate transcripts that allow our genes to be translated into proteins but the significance of this activity remains unclear. We observe a very strong induction of this RNA-editing activity when we activate A3A in epithelial cells.Based on these novel observations, we will use our unique tools to identify in detail how the A3A gene is switched on in epithelial cells that have been stimulated to divide and will establish the role that A3A plays in regulating this process. We will conduct a comprehensive survey of A3A-mediated RNA editing events and will test our hypothesis that this activity allows A3A to change the rate at which key proteins are made.This project will result in a step-change in our knowledge of A3A regulation and function, its importance in normal epithelial biology and in pathologies ranging from inflammation to viral infections and cancer. This knowledge will be vital if we are to successfully harness A3A as a drug target. It will also address a fundamental question regarding the role of A3A-mediated RNA editing in controlling how our genes are expressed.

当病毒进入我们的细胞并试图复制时，我们的身体对抗病毒感染的一种方法是攻击病毒基因组（DNA或RNA，取决于病毒）。一种与这种免疫反应有关的蛋白质APOBEC3A（A3A）修饰了胞嘧啶，这是DNA和RNA的四个构件之一，导致误差（突变）和病毒基因中断。除了某些称为巨噬细胞的专门免疫细胞外，通常在我们细胞中的高水平中没有发现A3a。它是针对感染的响应而打开的，并在保护我们免受一系列病毒中起着重要作用，但是在包括湿疹和牛皮癣在内的炎症状况中也被激活。尽管A3A有助于捍卫我们免受病毒感染的侵害，但这种保护是有代价的，因为我们和其他人表明它可以违背我们自己的基因，从而产生引起癌症的突变。大量研究证实，这一过程发生在很大一部分的癌症中，尤其是在组织（上皮）中产生的癌症，这些癌症（上皮）将嘴和喉咙，肺，乳房，膀胱和宫颈排列。 A3A不仅在癌症发育过程中突变我们的DNA，而且在患者接受化学疗法时，A3A似乎可以继续以这种流氓方式起作用。驱动抗药性，最终驱动治疗失败。这些知识激发了学术界和行业的倡议，以开发A3A抑制剂。可以阻止这种诱变活性的药物在接受化学疗法的患者中，从而防止肿瘤对治疗具有抗性。尽管这种方法具有改善数百万癌症患者的预后的潜力，但我们尚不了解A3A的控制方式以及它在正常健康的上皮细胞中所发挥的功能，而A3A突变的癌症会从中发展出来。没有这些知识，我们对触发流氓A3A活性的原因几乎没有什么想法，或者抑制A3A活性的副作用可能在患者中产生了什么。在此提案中，我们基于在培养的人类上皮细胞中研究A3A作出的三个关键发现，制定了一系列实验来解决这些问题。 1）我们发现，通过模仿上皮细胞中的伤口愈合反应，我们可以将A3A基因切换到远远高于这些细胞中先前看到的水平，并且由于这些细胞复制其DNA，该水平仍然保持很高，而DNA可能会易受流氓A3A活性的影响。 2）通过删除上皮细胞中的A3A基因，我们发现了A3A在调节这些细胞分裂速率中的先前未知作用，这对于了解我们是否要预期靶向A3A对癌症治疗的影响至关重要。 3）最近的研究表明，A3A可以改变许多细胞信使RNA，这是使我们的基因转化为蛋白质的中间转录物，但该活性的重要性尚不清楚。当我们在上皮细胞中激活A3A时，我们会非常强烈地诱导这种RNA编辑活性。基于这些新型观测值，我们将使用我们的独特工具详细识别A3A基因在已被刺激以分裂的上皮细胞中打开并确定A3A在该过程中发挥作用的作用。我们将对A3A介导的RNA编辑事件进行全面的调查，并将测试我们的假设，即该活动允许A3A改变制作关键蛋白质的速率。该项目将导致我们对A3A调节和功能的了解，其在正常上皮生物学和病毒疗法对病毒性感染和癌症中的重要性，其重要性是我们对A3A调节和功能的重要性。如果我们要成功利用A3A作为药物靶标，那么这些知识将至关重要。它还将解决有关A3A介导的RNA编辑在控制我们基因表达方式中的作用的基本问题。

项目成果

Differentiation signals induce APOBEC3A expression via GRHL3 in squamous epithelia and squamous cell carcinoma

分化信号通过 GRHL3 在鳞状上皮和鳞状细胞癌中诱导 APOBEC3A 表达

• DOI: 10.21203/rs.3.rs-3997426/v1
• 发表时间: 2024
• 作者: Fenton T