The MDR1 enhancesome--its activation and inhibition

描述：（应用摘要）P-糖蛋白（Pgp）首次被鉴定 由于其在多药耐药细胞中的过度表达， 大量化疗药物的外排。此外，最近 有证据表明，Pgp也可能在细胞凋亡中发挥更广泛的抗凋亡作用。 肿瘤细胞，因为过表达Pgp的细胞也表现出对一些 其他半胱天冬酶介导的凋亡诱导剂，包括血清饥饿，紫外线 照射、Fas配体和TNF。有趣的是，这些代理人中的许多人也 作为Pgp转录的诱导物，这表明Pgp的激活可能是Pgp转录的一部分。 肿瘤细胞的一般“应激反应”，并在细胞内发挥作用， 生长和死亡的决定对有毒刺激的反应。我们的实验室 长期以来，人们一直对调节转录的机制感兴趣， 人Pgp基因，MDR 1。我们最近观察到，MDR 1基因表达可以是 快速（在几分钟内）激活患者肿瘤暴露于 遗传毒性化疗剂阿霉素促使我们研究 多种“应激”诱导MDR 1转录的机制 剂.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，分化剂， 化疗药物和紫外线照射）集中在MDR 1的一个小区域 启动子，并发现该区域与多亚基相互作用， 复合物，我们称之为“MDR 1增强体”， 转录因子NF-Y、Sp1和PCAF。此外，我们还发现了一个 一种新的化疗剂ET-743，其通过以下途径抑制MDR 1的活化： 增强体，而不显著影响组成型MDR 1 转录。我们现在建议继续对“MDR 1”进行调查 1）鉴定和表征另外的组分 2）研究MDR 1增强体对MDR 1基因转录水平的影响。 诱导剂对MDR 1启动子处染色质重塑的影响; 3）继续我们的发现 多个Sp1家族成员可能是MDR 1增强子的组成部分， 对MDR 1转录有不同的影响; 4）继续研究 ET-743抑制MDR 1转录激活的机制， 长期目标是确定这一特定的转录靶点， 新的化疗剂。

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.