CHROMATIN ACTIVATION IN RETINOID-INDUCED APOPTOSIS

类维生素A是维生素A的代谢产物，对正常细胞和肿瘤细胞的生长、分化和死亡（凋亡）具有深远的影响。 虽然对维甲酸调节细胞增殖和分化的机制已经了解了很多，但对维甲酸诱导的细胞凋亡的分子机制知之甚少。 为了解决这个问题，我们最近获得了RO1资助（CA76088），以研究维甲酸诱导细胞凋亡的信号通路。 这些研究旨在确定类维生素A受体和信号通路（直接与间接效应）参与诱导体内细胞凋亡中的组织转氨酶。 在提交本申请时，不可能研究这些作用的分子机制，因为对将配体结合与转录激活联系起来的受体后机制知之甚少。 然而，在此期间，该领域取得了重要进展，发现（部分基于合作研究者的发现）类维生素A受体的配体活化将具有组蛋白乙酰转移酶活性的蛋白质募集到靶基因的启动子。 据推测，继发于组蛋白乙酰化的染色质结构的改变可能是配体依赖性转录激活的重要贡献者。 支持这一假设的实验证据主要是在模型系统中收集的。 本提案中包含的研究目标是确定类维生素A依赖性染色质乙酰化是否有助于激活经历类维生素A诱导的细胞凋亡的基因表达。 拟议的研究将针对两个具体目标。第一个将是在体外研究维甲酸诱导的髓性白血病细胞凋亡中维甲酸诱导的染色质结构变化。 第二个目的将是检查类维生素A对体内趾间蹼退化过程中发生凋亡的细胞中染色质结构的影响。 这两项研究的结果应提供新的信息历史乙酰化和去乙酰化的作用，在细胞凋亡在体外和体内。

Retinoids are metabolites of vitamin A that have profound effects on the growth, differentiation and death (apoptosis) of normal and neoplastic cells. While a lot has been learned of the mechanisms by which retinoids regulate cellular proliferation and differentiation remarkably little is known about the molecular mechanisms involved in retinoid - induced apoptosis. To address this problem, we were recently awarded an RO1 grant (CA76088) to investigate the signaling pathways involved in retinoid-induced apoptosis. These studies were designed to identify the retinoid receptors and signaling pathways (direct versus indirect effects) involved in the induction of the enzyme tissue transglutaminase in cells undergoing apoptosis in vivo. At the time this application was submitted it was not possible to investigate the molecular mechanism of these effects because little was known of the post-receptor mechanisms that linked ligand binding to transcriptional activation. In the interim however important progress has been made in this field with the discovery (based in part on the collaborating investigators findings) that ligand activation of retinoid receptors recruits proteins with histone acetyl transferase activity to the promoter of target genes. It has been hypothesized that alterations in chromatin structure secondary to histone acetylation may be an important contributor to the ligand - dependent activation of transcription. The experimental evidence in support of this hypothesis have been largely gathered in model systems. The goal of the studies included in this proposal will be to determine whether retinoid - dependent acetylation of chromatin contributes to the activation of gene expression in cells undergoing retinoid-induced apoptosis. The proposed studies will address two specific aims. The first will be to characterize retinoid -induced changes in chromatin structure in myeloid leukemia cells undergoing retinoid-induced apoptosis in vitro. The second aim will be to examine the effects of retinoids on chromatin structure in cells undergoing apoptosis during regression of the interdigital webs in vivo. The results of both of these studies should provide novel information on the role of historic acetylation and de-acetylation in cells undergoing apoptosis in vitro and in vivo.