RETINOID REGULATION OF TRANSGLUTAMINASE GENE EXPRESSION

类维生素A是维生素A的代谢产物， 正常和肿瘤细胞的生长、分化和死亡。 维甲酸作为化学预防和化学治疗的功效 用于治疗人类癌症的药物引起了人们对 维甲酸作用的分子机制。 我们一直 类维生素A诱导肿瘤细胞凋亡的能力 细胞，并使用组织转氨酶的诱导 作为分子探针来研究类维生素A 调节基因表达。 组织转氨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。 的 在垂死细胞中诱导转氨酶提供了一种独特的 有机会研究控制基因的分子机制， 在凋亡过程中表达。 我们已经分离了4.0 kB的5 '侧翼DNA 从转氨酶基因启动子，并已显示在转基因 启动子的这个片段包含了所有的信息， 必需的指导转氨酶启动子的激活， 凋亡细胞在正常肢体发育过程中形成。 我们有 证明类维生素A是维生素A的关键调节剂 该启动子的转录活性，并确定了两个顺式- 调节元件，三联类维生素A反应元件（RRE 1）和 一个保守的元件（HR-1），其在调节 该启动子的转录活性。 我们还证明 异二聚体RXR/RAR和同二聚体RXR/RXR复合物都可以 结合并激活转氨酶基因的转录。 的 我们研究的下一步将是评估 转谷氨酰胺酶基因在体内细胞中的表达 正常肢体发育过程中的细胞凋亡。 我们将评估 类维生素A受体信号通路控制这种表达， 基因是凋亡细胞。我们还将研究直接和 对转氨酶表达的激活的间接影响。 这些研究应该为分子机制提供新的见解 参与体内类维生素A诱导的细胞凋亡。

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.