A direct role for cholesterol in the regulation of transcription

在任何给定的细胞中，只有特定的基因会被激活(或表达)，正是表达的基因的特定组合决定了细胞的类型(例如肌肉、皮肤或神经细胞)。因此，基因表达的控制是细胞特性的核心。我们发现了一种多蛋白质复合体，它使用脂类来调节基因。这是非常不寻常的，因为脂质通常与细胞膜有关。我们的假设是，这种复合体使用脂类与细胞核内的其他因子形成联系，这一过程是基因在开启和关闭状态之间切换的中心。了解脂类如何调节基因将为控制不同细胞类型形成的事件提供重要的见解，并可能为使用脂类作用药物治疗由基因调节异常引起的疾病提供机会。在这项建议中，我们提出了必要的脂类胆固醇在关闭基因方面发挥积极作用的证据。我们发现，胆固醇指导DNA上蛋白质之间相互作用的形成，然后阻止附近基因的表达。在这项提案中，我们将确定被胆固醇关闭的基因。这将通过阻止胆固醇的产生，然后测量基因表达，以及通过使用不再与胆固醇结合的突变蛋白来实现。然后，我们将确定胆固醇如何改变DNA上蛋白质复合体的形成，并确定指导胆固醇开关活动的关键蛋白质。最后，将测试胆固醇对改变基因表达的酶活性的影响。该提案的结果将增强我们对胆固醇在基因调控中的作用的理解，并为与细胞膜无关的脂质的功能提供新的见解。

In any given cell, only certain genes will be switched on (or expressed) and it is the specific combination of expressed genes that determines the type of cell (for example a muscle, skin or nerve cell). Thus, the control of gene expression lies at the heart of cellular identity. We have discovered a multi-protein complex that uses lipids to regulate genes. This is highly unusual because lipids are normally associated with cell membranes. Our hypothesis is that this complex uses lipids to form contacts with other factors within the cell nucleus and that this process is central to switching genes between an on and off state. Understanding how lipids regulate genes will provide important insights into the events that control the formation of different cell types and may also provide opportunities to use lipid-acting drugs to treat diseases that result from aberrant gene regulation.In this proposal we present evidence that the essential lipid cholesterol can play an active role in turning genes off. We find that cholesterol directs the formation of interactions between proteins on the DNA that then blocks expression of nearby genes. In this proposal we will determine the genes that are switched off by cholesterol. This will be achieved by blocking cholesterol production and then measuring gene expression and also by using mutant proteins that no longer bind to cholesterol. We will then determine how cholesterol changes the formation of protein complexes on the DNA and identify the critical proteins that are directing the action of the cholesterol switch. Finally, the effect of cholesterol on the activities of enzymes that alter gene expression will be tested. The outcomes of the proposal will enhance our understanding of the role of cholesterol in gene regulation and provide new insights into the function of lipids that are not associated with cellular membranes.