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TOPOISOMERASE II--GENE REGULATI0N AND DRUG RESISTANCE

拓扑异构酶 II——基因调控和耐药性

基本信息

批准号：
2871734
负责人：
DALE P SUTTLE
金额：
$ 16.26万
依托单位：
UNIVERSITY OF TENNESSEE HEALTH SCI CTR
依托单位国家：
美国
项目类别：
财政年份：
1989
资助国家：
美国
起止时间：
1989-04-10 至 2001-09-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/2871734
关键词：
3T3 cells DNA damage DNA replication DNA topoisomerases antineoplastics drug resistance enzyme inhibitors enzyme mechanism gene expression genetic promoter element genetic regulation isozymes neoplasm /cancer genetics nucleic acid sequence oncogenes p53 gene /protein transcription factor tumor suppressor genes

项目摘要

Topoisomerase II is an essential enzyme for such cell functions as DNA replication and chromosome segregation. Acting as a dimer, topoisomerase II passes a double stranded DNA segment through a transient double strand break in a second DNA strand to modify the topology of the DNA molecule. Two isoforms of topo II (alpha and beta) are present in mammalian cells. Topo IIbeta protein levels in the cell are known to directly correlate with cell proliferation rate and topo IIalpha expression is cell cycle dependent. Topo IIbeta levels are much more constant throughout the cell cycle and the protein is more tightly associated with the nuclear scaffold. Because of the interaction of topo II with DNA in critical cellular functions, it is both a unique and natural target for anticancer drugs that can inhibit cell growth or induce cell death. However, all too often, tumor cell develop resistance to topo Il-targeted drugs. Although the drug resistance can result from structural mutations in the topo II protein, decreased levels to topo II in the cell may more often be the primary factor contributing to the cells decreased drug sensitivity. The major objective of this application is to identify and characterize the transcription factors that regulate the expression of topoisomerase IIalpha. These studies will focus on both the normal cell cycle-dependent expression of topo IIalpha and the altered expression of topo IIalpha in drug-resistant cells. These studies will include characterization of the mechanism by which topo Il-targeted drugs and the DNA damage resulting from the drug's action effects the level of topo IIalpha in the cell. Drug induced DNA strand breaks induce the tumor suppressor gene p53, which serves as a G1 checkpoint control for DNA damage. Wild type p53 has an antiproliferative and antitumorgenetic effect resulting from specific activation or suppression of gene transcription. On the other hand, mutant p53 functions as an oncogene, promoting tumorgenesis. Our initial studies provide evidence that wild type p53 may serve as a negative controlling factor for the regulation of topo Ha expression. The topo IIalpha promoter sequence required for p53 downregulation of topo IIalpha and the transcription factors interacting with the topo IIalpha promoter element will be identified and characterized. Analysis of topo II regulation in normal and tumor cells will yield vital information for the effective use of the clinically important topo II-targeted drugs.

拓扑异构酶II是DNA等细胞功能的必需酶复制和染色体分离。作为二聚体，拓扑异构酶 II使双链DNA片段通过瞬时双链在第二条DNA链中断裂以修饰DNA分子的拓扑结构。哺乳动物细胞中存在两种拓扑异构体II（α和β）。已知细胞中的拓扑异构酶II β蛋白水平与细胞增殖率和topo Ⅱ α表达与细胞周期有关依赖。在整个细胞中，蛋白质与细胞核骨架的结合更紧密。由于topo II与DNA在关键细胞中的相互作用，功能，它既是抗癌药物的独特和天然靶点，可以抑制细胞生长或诱导细胞死亡。然而，肿瘤往往细胞对拓扑异构酶II靶向药物产生耐药性。虽然药物抗性可由Topo II蛋白的结构突变引起，细胞中拓扑异构酶II水平降低可能更经常是主要的导致细胞药物敏感性降低的因素。本申请的主要目的是识别和表征调节拓扑异构酶表达的转录因子第二章这些研究将集中在正常细胞周期依赖性 Topo II α的表达和Topo II α表达的改变，耐药细胞这些研究将包括表征拓扑异构酶II靶向药物的作用机制以及药物的作用影响细胞中拓扑异构酶II α的水平。药物诱导的DNA链断裂诱导肿瘤抑制基因p53，作为DNA损伤的G1检查点对照。野生型p53具有抗增殖和抗肿瘤遗传效应，基因转录的激活或抑制。另一方面，变种人 p53作为致癌基因发挥作用，促进肿瘤发生。我们最初的研究提供了野生型p53可以作为阴性对照的证据调节topo Ha表达的因子。Topo II alpha启动子 p53下调topo II α所需的序列，与topo Ⅱ α启动子元件相互作用的转录因子将被识别和表征。拓扑异构酶II的调控分析正常细胞和肿瘤细胞将产生重要的信息，临床上重要的拓扑异构酶II靶向药物