Role of NFY in Irradiation Induced Gene activation

所有器官的一个主要组成部分是血管系统，它为营养交换提供了毛细血管网络。在许多类型的癌症的治疗中使用放射疗法导致作为内皮细胞损伤的结果的立即和延迟的血管损伤。因此，对血管内皮细胞的损伤是放射治疗引起的并发症的主要原因，包括血栓形成、过早的冠状动脉硬化和心肌梗死或纤维化。辐射导致内皮细胞中抗凝血因子的表达降低和促凝血因子（如血管性血友病因子（VWF））的表达增加。血液中的循环VWF分子被认为主要负责血小板粘附的初始步骤。VWF表达的增加对辐射的反应导致血小板沉积水平升高，这可能是辐射治疗后血栓形成的主要原因。血小板血栓的形成通过在损伤后保持血管完整性提供了一种防御机制，然而它可以加速诸如动脉粥样硬化的疾病。已经鉴定了许多辐射响应性转录因子，其激活内皮细胞中的一些下游辐射诱导基因，然而包括VWF在内的许多其他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展中的主要作用之外，VWF是具有高度限制的内皮特异性表达模式的分子，其提供了研究响应于辐射的内皮特异性基因调控的机制的机会。在我们的研究中，我们发现电离辐射导致VWF转录上调。我们现在已经鉴定了VWF启动子中的序列CCAAT作为辐射响应性顺式作用元件。我们还证明了NFY转录因子与CCAAT元件相互作用并介导辐射诱导的VWF启动子激活。我们推测辐射导致NFY的翻译后修饰，从而增加其反式激活功能。我们现在提出的具体目标1），以确定响应于辐射的NFY的翻译后修饰的性质;和具体目标2），以确定导致响应于辐射的内皮细胞的NFY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.