KERATINOCYTES--MODULATION BY RETINOIC ACID

类维生素A是一类化合物，其是治疗糖尿病的有效治疗剂。 一些皮肤病。 为了改善治疗， 这些疾病，有必要阐明机制， 类维生素A，如全反式维甲酸（RA），发挥其抗- 增殖效应 因此，这些研究的长期目标是， 以确定RA如何抑制角质形成细胞生长。 的重要举措 RA是抑制角质形成细胞的鸟氨酸脱羧酶（OD），一种酶 其产物多胺是细胞生长所必需的。 是 因此，建议确定ODC基因表达的抑制是否是一种 类维生素A作用的直接后果以及这种抑制是如何发挥作用的。 这些实验旨在验证RA抑制ODC的假设 通过RA受体（RAR）介导的机制进行基因转录。 这 将通过（1）确定RA和/或放线菌酮的作用来检查 使用Run-on对人类ODC基因的相对转录率进行了研究， （2）确定哪种RAR在角质形成细胞中表达， 区分细胞RA结合蛋白的作用， 通过使用嵌合RAR/雌激素， 将转染到角质形成细胞中的受体;（3）鉴定顺式- 与反式作用因子相互作用导致RA的作用DNA元件- 介导的ODC基因转录的变化，使用体外足迹法， 凝胶阻滞试验，以及连接到 胸苷激酶-β-珠蛋白基因;和（4）分离编码非- RAR反式作用因子参与RA作用。 阐明 RA抑制ODC基因表达的机制将产生 关于维甲酸如何发挥其抗增殖作用重要信息 方面的影响.

Retinoids are a class of compounds which are potent therapeutic agents for a number of dermatological diseases. In order to improve treatment of these diseases, it is necessary to elucidate the mechanism whereby retinoids, such as all-trans-retinoic acid (RA), exert their anti- proliferative effects. The long term goal of these studies is, therefore, to determine how RA inhibits keratinocyte growth. An important action of RA is keratinocytes is to inhibit ornithine decarboxylase (OD), an enzyme whose products, the polyamines, are necessary for cell growth. It is therefore proposed to determine if inhibition of ODC gene expression is a direct consequence of retinoid action and how this repression is exerted. These experiments re designed to test the hypothesis that RA suppresses ODC gene transcription through a RA receptor (RAR)-mediated mechanism. This will be examined by (1) determining the effects of RA and/or cycloheximide on the relative transcription rates of the human ODC gene using run-on transcription; (2) determining which RAR is expressed in keratinocytes and discriminating between the actions of the cellular RA binding protein and the alpha-, beta-, and gamma-RARs through the use of chimeric RAR/estrogen receptors that will be transfected into keratinocytes; (3) identifying cis- acting DNA elements that interact with trans-acting factors to cause RA- mediated changes in ODC gene transcription, using in vitro footprinting, gel retardation assays, and transfectin of isolated elements ligated to the thymidine kinase-beta-globin gene; and (4) isolation of cDNAs encoding non- RAR trans-acting factors which are implicated in RA action. Elucidation of the mechanisms whereby RA suppresses ODC gene expression will yield important information on how retinoids exert their anti-proliferative effects.