The MDR1 enhancesome--its activation and inhibition

描述：(应用摘要)P-糖蛋白(Pgp)首次被鉴定 通过它在多药耐药细胞中的过度表达，在那里它介导 大量化疗药物的外流。此外，最近 有证据表明，Pgp也可能在心脏疾病中发挥更普遍的抗凋亡作用。 肿瘤细胞，因为过度表达Pgp的细胞也表现出对一些 其他caspase介导的凋亡诱导因子，包括血清饥饿，UV 照射、Fas配体和肿瘤坏死因子。有趣的是，这些特工中的许多人也采取行动 作为Pgp转录的诱导者，提示Pgp的激活可能是 肿瘤细胞的一般“应激反应”，并在细胞内发挥作用 对有毒刺激做出的生长和死亡决定。我们实验室已经有了 长期以来，人们对调控转录的机制感兴趣 人Pgp基因，mdr1。我们最近观察到MDR1基因的表达可以是 在患者肿瘤内暴露于 基因毒性化疗药物阿霉素促使我们调查 多种“应激”诱导mdr1转录的机制 探员们。令人惊讶的是，我们发现来自看似不同的信号 试剂(包括染色质修饰剂、分化试剂、 化疗药物和紫外线照射)聚集在mdr1的一小部分区域 启动子，并发现该区域与一个多亚基相互作用 复杂，我们称之为“MDR1增强版”，其中包括 转录因子NF-Y、Sp1和PCAF。此外，我们还确定了一种 新型化疗药物ET-743通过抑制MDR1的激活 增强作用，但不会显著影响构成MDR1 抄写。我们现在提议继续调查“多药耐药” 和ET-743：1)以识别和表征其他组件 2)研究mdr1基因转录增强的作用 Mdr1启动子染色质重塑的诱导物；3)继续我们的发现 多个Sp1家族成员可能是MDR1增强型和 对mdr1转录有不同的影响，4)继续研究 ET-743抑制MDR1转录激活的机制 确定该基因的特定转录靶点的长期目标 新型化疗药物。

DESCRIPTION: (Application Abstract) P-glycoprotein (Pgp) was first identified by virtue of its overexpression in multidrug-resistant cells, where it mediates the efflux of a large number of chemotherapeutic agents. Moreover, recent evidence suggests that Pgp may also play a more general anti-apoptotic role in tumor cells, since cells overexpressing Pgp also exhibit resistance to a number of other caspase-mediated apoptotic inducers, including serum starvation, UV irradiation, Fas ligand and TNF. Interestingly, many of these agents also act as inducers of Pgp transcription, suggesting that activation of Pgp may be part of a general "stress response" of tumor cells, and play a role in cellular growth and death decisions in response to toxic stimuli. Our laboratory has had a long-standing interest in the mechanisms regulating the transcription of the human Pgp gene, MDR1. Our recent observation that MDR1 gene expression can be rapidly (within minutes) activated within patient tumors exposed to the genotoxic chemotherapeutic agent doxorubicin has prompted us to investigate the mechanism underlying transcriptional induction of MDR1 by a variety of "stress" agents. Surprisingly, we have found that signals from seemingly disparate agents (including chromatin modifiers, differentiation agents, chemotherapeutics and UV irradiation) converge on a small region of the MDR1 promoter, and have found that this region interacts with a multisubunit complex, which we refer to as the "MDR1 enhancesome," that includes the transcription factors NF-Y, Sp1 and PCAF. Furthermore, we have identified a novel chemotherapeutic agent, ET-743, which inhibits activation of MDR1 through the enhancesome, without significantly affecting constitutive MDR1 transcription. We now propose to continue our investigations of the "MDR1 enhancesome" and ET-743: 1) To identify and characterize additional components of the "MDR1 enhancesome"; 2) To investigate the effect of transcriptional inducers on chromatin remodeling at the MDR1 promoter; 3) To pursue our finding that multiple Sp1 family members may be components of the MDR1 enhancesome and have divergent effects on MDR1 transcription and 4) To continue to investigate the mechanism by which ET-743 inhibits activation of MDR1 transcription, with the long-term goal of identifying the specific transcriptional target of this novel chemotherapeutic agent.