RETINOID REGULATION OF TRANSGLUTAMINASE GENE EXPRESSION

维甲酸是维生素A的代谢物，对 正常细胞和肿瘤细胞的生长、分化和死亡。 维甲酸作为化学预防和化疗的疗效 在治疗人类癌症方面有用的药物引起了人们对 维甲酸作用的分子机制。我们一直在 对维甲酸诱导肿瘤细胞凋亡能力的兴趣 细胞，并使用了组织转谷氨酰胺酶的诱导 作为分子探针研究维甲酸类化合物的作用机制 调控基因表达。组织转谷氨酰胺酶是一种蛋白质交叉- 在凋亡细胞中积累到高水平的连接酶。这个 在垂死的细胞中诱导谷氨酰胺转氨酶提供了一种独特的 研究控制基因的分子机制的机会 在细胞凋亡过程中的表达。我们已经分离出4.0kB的5‘侧翼DNA 来自转谷氨酰胺酶基因启动子，并在转基因中显示 老鼠认为这段启动子包含了所有的信息 转谷氨酰胺酶启动子在体内的激活所必需的 凋亡细胞形成于正常肢体发育过程中。我们有 证明类维A酸类化合物是 该启动子的转录活性，并鉴定了两个顺式- 调控元件、三方维甲酸反应元件(RRE1)和 一种保守元件(HR-1)，它在调节 该启动子的转录活性。我们还展示了 异二聚体RXR/RAR和同二聚体RXR/RXR络合物都可以 结合并激活转谷氨酰胺酶基因的转录。这个 我们研究的下一步将是评估控制 转谷氨酰胺酶基因在体内的表达 正常肢体发育中的细胞凋亡性死亡。我们将评估 控制其表达的维甲酸受体信号通路 基因是一种凋亡细胞。我们还将调查直接和 转谷氨酰胺酶表达激活的间接影响。 这些研究应该为分子机制提供新的见解。 参与维甲酸诱导的体内细胞凋亡。

Retinoids are vitamin A metabolites that have profound effects on the growth, differentiation and death of both normal and neoplastic cells. The efficacy of retinoids as both chemopreventative and chemotherapeutic agents useful in the treatment of human cancers has lead to interest in the molecular mechanisms that underlie retinoid action. We have been interest in the ability of retinoids to induce apoptosis in neoplastic cells and have used the induction of the enzyme tissue transglutaminase as a molecular probe to investigate the mechanisms by which retinoids regulate gene expression. Tissue transglutaminase is a protein cross- linking enzyme that accumulates to high levels in apoptotic cells. The induction of transglutaminase in dying cells provides a unique opportunity to investigate the molecular mechanisms that control gene expression during apoptosis. We have isolated 4.0 kB of 5'-flanking DNA from the transglutaminase gene promoter and have shown in transgenic mice that this segment of the promoter includes all of the information necessary to direct the activation of the transglutaminase promoter in the apoptotic cells formed during normal limb development. We have demonstrated that retinoids are critical regulators of the transcriptional activity of this promoter and have identified two cis- regulatory elements, a tripartite retinoid response element (RRE1) and a conserved element (HR-1) that co-operate in regulating the transcriptional activity of this promoter. We have also demonstrated that both hetrodimeric RXR/RAR and homodimeric RXR/RXR complexes can bind to and activate transcription of the transglutaminase gene. The next step in our studies will be to evaluate the factors that control the expression of the transglutaminase gene in vivo, in cells undergoing apoptotic cell death during normal limb development. We will evaluate the retinoid receptor signaling pathways that control expression of this gene is apoptotic cells. We will also investigate the role of direct and indirect effects on the activation of transglutaminase expression. These studies should provide new insights into the molecular mechanisms involved in retinoid - induced apoptosis in vivo.