TOPOISOMERASE III AND GENOMIC INSTABILITY

描述：（改编自研究者摘要）失调 同源重组可导致基因组不稳定性，其表现为 通过基因倒位、缺失、扩增、易位和缺失， 杂合性基因组的不稳定性可以提供一个驱动力， 获得多种遗传改变并可能导致肿瘤发生。 真核拓扑异构酶III首先在酵母中被鉴定， 缺失突变体的表型，包括 重复序列、生长缓慢和孢子形成缺陷。变种人也 显示细胞周期中的晚期S/G2延迟，端粒缩短， 增加染色体丢失。拓扑异构酶III的物理和功能 与属于蛋白质家族的酵母DNA解旋酶SGS 1相互作用 包括人类布鲁姆综合征和沃纳综合征基因产物。的 拓扑异构酶III和解旋酶之间相互作用在进化上是 保守的SGS 1突变抑制拓扑异构酶III突变表型。 sgs 1突变体也表现出过早的细胞老化，SIR 3的重新分布， 沉默蛋白复合物从端粒到核仁， 碎片化酵母拓扑异构酶III的人类同源物hTOP 3a具有 以前被分离出来，并建议参与遗传不稳定性， 共济失调毛细血管扩张细胞。他最近克隆了 第二种人拓扑异构酶III hTOP 3b的选择性剪接形式。他 也证明了hTOP 3b的最大基因产物可以与 酵母SGS 1蛋白和hTOP 3B的表达可以部分地弥补慢 酵母拓扑异构酶III突变体的生长表型。在这份提案中，他 目的：1）比较不同植物的生化特性和生物学功能， 人拓扑异构酶III蛋白; 2）确定是否存在生长， 表达增强或破坏的细胞系中的遗传变化 hTOP 3a和hTOP 3b同种型;和3）鉴定和表征 与hTOP 3a和hTOP 3b特异性相互作用。这些研究的结果将 提供了有关各种人类生理作用的重要信息， 拓扑异构酶III基因产物及其对维持基因组 完整相互作用蛋白的鉴定和相互作用蛋白的阐明 相互作用机制可以提供这些蛋白质如何调节 基因组稳定性、细胞生长、细胞老化以及最终癌症发展。

DESCRIPTION: (Adapted from the investigator's abstract) Dystregulated homologous recombination can lead to genomic instability, which is manifested by gene inversion, deletion, amplification, translocation, and loss of heterozygosity. Genomic instability can provide a driving force for the acquisition of multiple genetic alteractions and may lead to tumorigenesis. Eukaryotic topoisomerase III was first identified in yeast based on the phenotypes of the deletion mutant, which include hyper-recombination of repetitive sequences, slow growth, and defects in sporulation. The mutant also demonstrates late S/G2 delay in the cell cycle, shortened telomeres, and increased chromosomal losses. Topoisomerase III physically and functionally interacts with a yeast DNA helicase SGS1, which belongs to a family of proteins including the human Bloom's syndrome and Werner's syndrome gene products. The interaction between topoisomerase III and helicase is evoluationarily conserved. Mutation of SGS1 suppresses the topoisomerase III mutant phenotypes. The sgs1 mutant also exhibits premature cell aging, redistribution of SIR3 silencing protein complex from telomeres to nucleolus, and nucleolar fragmentation. A human homologue of yeast topoisomerase III, hTOP3a, has previously been isolated and suggested to be involved in genetic instability of ataxia telangiectasia cells. He has recently cloned the cDNAs for the alternative splice forms of a second human topoisomerase III, hTOP3b. He has also demonstrated that the largest gene product of hTOP3b can interact with the yeast SGS1 protein, and expression of hTOP3B can partially complement the slow growth phenotype of the yeast topoisomerase III mutant. In this proposal, he propose: 1) to compare the biochemical properties and biological functions of the human topoisomerase III proteins; 2) to determine if there are growth and genetic changes in the cell lines with enhanced or disrupted expression of hTOP3a and hTOP3b isoforms; and 3) to identify and characterize proteins which interact specifically with hTOP3a and hTOP3b. The results of these studies will provide significant information about the physiological roles of various human topoisomerase III gene products and their effects on maintaining genomic integrity. Identification of the interacting proteins and elucidation of the interaction mechanism may provide insights into how these proteins regulate genomic stability, cell growth, cell aging, and ultimately, cancer development.