Role of NFY in Irradiation Induced Gene activation

所有器官的一个主要组成部分是一个血管系统，它为营养交换提供一个毛细血管网络。在许多类型的癌症治疗中使用放射治疗会导致血管的直接损伤和延迟性损伤，这是内皮细胞损伤的结果。因此，血管内皮细胞的损伤是导致并发症的主要原因，包括血栓形成、过早的冠状动脉硬化和心肌梗死或纤维化，这些都是放射治疗的结果。照射后内皮细胞抗凝血剂表达减少，促凝血因子表达增加，如血管性血友病因子。血液中循环中的VWF分子被认为主要负责血小板黏附的初始步骤。照射后VWF表达增加会导致血小板沉积水平升高，这可能是放射治疗后血栓形成的主要原因。血小板血栓的形成通过保护损伤后血管的完整性提供了一种防御机制，但它也可以诱发动脉粥样硬化等疾病。目前已发现多种辐射反应转录因子激活血管内皮细胞辐射诱导下游基因，但包括VWF在内的许多基因的辐射诱导机制尚不清楚。除了在辐射诱导的血管疾病的发生发展中起主要作用外，VWF还是一种具有高度限制性的内皮特异性表达模式的分子，这为研究辐射引起的内皮特异性基因调控机制提供了机会。在我们的研究中，我们发现电离辐射导致VWF转录上调。我们现在已经确定VWF启动子中的CCAAT序列是辐射反应顺式作用元件。我们还证明了NFY转录因子与CCAAT元件相互作用，并介导了辐射诱导的VWF启动子激活。我们假设辐射导致NFY的翻译后修饰，从而增加其反式激活功能。我们现在建议有针对性地)确定NFY对辐射的翻译后修饰的性质；以及特定目的2)确定导致NFY对内皮细胞辐射反应修饰的分子机制。

A major component of all organs is a vascular system that provides a network of capillary vessels for nutrient exchange. The use of irradiation therapy in treatment of many types of cancer results in both immediate and delayed vascular damage that is a consequence of injury to endothelial cells. Damage to the vascular endothelial cells is thus a major cause of complications including, thrombus formation, premature coronary arteriosclerosis, and myocardial infarction, or fibrosis, that occur as a consequence of irradiation therapy. Irradiation results in a decreased expression of anti-coagulant and an increased expression of pro-coagulant factors, such as von Willebrand factor (VWF) in endothelial cells. The circulating VWF molecules in the blood are proposed to be mainly responsible for initial steps of platelet adhesion. Increased VWF expression in response to irradiation results in elevated levels of platelet deposition, which may be a major cause of thrombus formation after irradiation therapy. The formation of platelet thrombi provides a defense mechanism by preserving the vascular integrity after injury, however it can precipitate diseases such as atherosclerosis. A number of irradiation responsive transcription factors have been identified that activate some of the downstream irradiation inducible genes in endothelial cells, however the mechanism of irradiation induction of many other genes including that of VWF is not known. In addition to its major role in development of irradiation induced vascular disease, VWF is a molecule with a highly restricted endothelial specific expression pattern that provides an opportunity to investigate the mechanism of endothelial specific gene regulation in response to irradiation. In our studies, we have found that ionizing radiation results in transcriptional upregulation of VWF.. We have now identified the sequence CCAAT in the VWF promoter as the irradiation responsive cis- acting element. We have also demonstrated that NFY transcription factor interacts with the CCAAT element and mediates the irradiation induced VWF promoter activation. We hypothesize that irradiation results in posttranslational modification of NFY thus increasing its transactivation function. We now propose in specific aim l) to determine the nature of posttranslational modification of NFY in response to irradiation; and in specific aim 2) to determine the molecular mechanism that leads to NFY modification in response to irradiation of endothelial cells.