REGULATION OF PGP1 MRNA IN MULTIDRUG-RESISTANT CELLS

多药耐药(MDR)仍然是 化疗成功。尽管对MDR的实验室研究和 在过去的几年里，诊所的发展速度令人印象深刻 多年来，有几个关键问题仍然没有得到回答。人们对此知之甚少 编码P-糖蛋白基因的调控机制(S) 可能是药物外排泵，其过度表达至少部分是， 对抗性表型负责。我们的实验室正试图 在正常细胞的发育和发育过程中定义这些机制 差异化以及在开发和维护 多药耐药表型。我们建议研究这些机制， 首先，仔细剖析 仓鼠pgp1基因的结构性表达。我们最近 转录起始点的差异利用鉴定 药物敏感和耐药细胞之间的关系表明了一种机制 Pgp1在无基因扩增条件下的过表达 放线菌素D(ActD)-选择的细胞；我们研究的长期目标是 为了定义这样的机制并确定转录或后转录- Pgp1表达增加的转录因子 多药耐药细胞中的基因。 具体目标1中概述的实验旨在定义 DNA序列元件和构成所需的蛋白质因子 仓鼠pgp1基因的表达。最终，我们希望确定 DNA和蛋白质因子参与组织特异性表达 Pgp1，以地鼠肝和肝细胞为模型系统。此外， 我们将研究差异利用背后的机制 Pgp1转录起始点。在具体目标2中，我们将进一步 通过检测pgp1基因的转录调控来剖析其转录调控 在无细胞转录系统中表达，长期目标是 在体外重建组织特异性转录。在具体目标3中， 我们建议研究转录后机制的作用 Pgp1在药物敏感与药物敏感中的表达调控 耐药细胞。

Multidrug resistance (MDR) remains one of the major obstacles to successful chemotherapy. Although the study of MDR in the laboratory and in the clinic has progressed at an impressive rate within the past several years, several critical questions remain unanswered. Little is known about the mechanism(s) regulating the genes that encode P-glycoprotein, the putative drug efflux pump whose overexpression is, at least in part, responsible for the resistant phenotype. Our laboratory is attempting to define these mechanisms in normal cells during development and differentiation as well as during the development and maintenance of the multidrug-resistant phenotype. We propose to examine these mechanisms, beginning with a careful dissection of the components required for the constitutive expression of the hamster pgp1 gene. Our recent identification of a differential utilization of transcription start sites between drug-sensitive and drug-resistant cells suggests a mechanism for the overexpression of pgp1 in the absence of gene amplification in actinomycin D (ActD)-selected cells; a long-range goal of our studies is to define such a mechanism and determine the transcriptional or post- transcriptional factors underlying the increased expression of the pgp1 gene in MDR cells. The experiments outlined in Specific Aim 1 are directed at defining the DNA sequence elements and protein factors required for the constitutive expression of the hamster pgp1 gene. Ultimately, we hope to identify the DNA and protein factors involved in the tissue-specific expression of pgp1, using hamster liver and hepatocytes as a model system. Furthermore, we will investigate the mechanism underlying the differential utilization of pgp1 transcription initiation sites. In Specific Aim 2, we will further dissect the transcriptional regulation of the pgp1 gene by examining its expression in a cell-free transcription system, with a long-range goal of reconstituting tissue-specific transcription in vitro. In Specific Aim 3, we propose to investigate the role that post-transcriptional mechanisms play in the regulation of pgp1 expression in drug-sensitive vs. drug- resistant cells.