TOPOISOMERASE II--GENE REGULATI0N AND DRUG RESISTANCE

拓扑异构酶II是DNA等细胞功能所必需的酶 复制和染色体分离。作为一种二聚体，拓扑异构酶 Ii使双链DNA片段通过瞬时双链 打断第二条DNA链，以改变DNA分子的拓扑结构。 哺乳动物细胞中存在两种TOPO II亚型(α和β)。 已知细胞中的Topo IIbeta蛋白水平与 细胞增殖率和Topo IIpha的表达是细胞周期 依附的。Topo IIbeta水平在整个细胞内更加恒定 循环，蛋白质与核支架联系更紧密。 因为在关键细胞中Topo II与DNA相互作用 功能，它既是抗癌药物独特的天然靶点 可抑制细胞生长或诱导细胞死亡。然而，肿瘤往往是 细胞对Topo Il靶向药物产生抗药性。虽然这种药 抗药性可以由Topo II蛋白的结构突变引起， 细胞内Topo II水平的降低可能更多地是主要的 导致细胞对药物敏感性降低的因素。 这个应用程序的主要目标是识别和表征 调控拓扑异构酶表达的转录因子 我是阿尔法。这些研究将集中在两个正常的细胞周期依赖 TOPOⅡα的表达及TOPOⅡα表达的改变 耐药细胞。这些研究将包括对 TOPO-IL靶向药物的作用机制及其对DNA的损伤 药物的作用会影响细胞内Topo IIpha的水平。 药物诱导的DNA链断裂诱导肿瘤抑制基因P53，该基因 作为DNA损伤的G1检查点控制。野生型p53有一个 特异性抗增殖和抗肿瘤作用 基因转录的激活或抑制。另一方面，变种人 P53作为癌基因发挥作用，促进肿瘤的发生。我们的初步研究 提供证据表明野生型p53可能起到负性控制作用 Topo Ha表达调控因子。Topo IIpha启动子 P53下调Topo IIpha所需的序列和 与Topo IIpha启动子元件相互作用的转录因子 将被识别和刻画。TOPO II在中国的调控分析 正常细胞和肿瘤细胞将为有效使用提供重要信息 临床上重要的TOPO II靶向药物。

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.