CHROMATIN REPLICATION AND HEAT-INDUCED CELL DEATH

本提案的总体目标是确定 高温（40至48度）和 辐射（0至100戈伊）暴露对DNA复制的影响， 哺乳动物细胞，以及病变在DNA复制中的作用， 热或热辐射联合诱导S期细胞 细胞毒 加热和/或辐照的S相的容量 细胞：重新分配在细胞核聚合的DNA 将这些新生的DNA加工成更高级的 顺序（螺线管）染色质结构，并最终连接这个 将确定DNA完全进入染色体大小的DNA。 的 我们将在加热的细胞中测试的模型是， 核基质或其相关结构或大分子， 导致DNA中的残留损伤在 高温暴露 类似的模型将被测试， 确定S期细胞是否对辐射敏感 敏感性共济失调毛细血管扩张人类细胞，xrs CHO双 链断裂修复突变体或“野生型”细胞暴露于咖啡因 在X射线照射过程中，这些细胞不能 将复制的DNA完全连接到染色体中。 核 在加热的细胞中检查的变化是热的 核基质蛋白变性， 核蛋白和RNA的核基质和 拓扑异构酶的潜在不可逆缔合 核基质附近的DNA上。 我们将确定 DNA复制过程中的这些损伤是否 细胞导致DNA链断裂的长期存在， DNA在细胞加热过程中复制， 染色体畸变形成和细胞毒性。

The overall objective of this proposal is to determine the combined effect(s) of hyperthermia (40 to 48 degree) and radiation (0 to 100 Gy) exposure on DNA replication in mammalian cells, and the role of lesions in DNA replication in heat-, or combined heat and radiation-induced S phase cell cytotoxicity. The capacity of heated and/or irradiated S phase cells: to redistribute DNA being polymerized at the nuclear matrix into bulk DNA, to process this nascent DNA into higher- order (solenoid) chromatin structure, and ultimately to ligate this DNA fully into chromosome-sized DNA will be determined. The model we will test in heated cells is that long-term damage to the nuclear matrix, or its associated structures or macromolecules, results in residual lesions in DNA being replicated during hyperthermic exposure. A similar model will be tested to determine whether S phase cell sensitivity in the radiation sensitive ataxia telangiectasia human cells, the xrs CHO double strand break repair mutants or "wild-type" cells exposed caffeine during X irradiation results from the failure of these cells to ligate replicating DNA fully into chromosomes. The nuclear alterations being examined in heated cells are the thermal denaturation of nuclear matrix protein(s), the precipitation of nuclear protein and RNA onto the nuclear matrix and the potentially irreversible association of the topoisomerase enzymes onto DNA adjacent to the nuclear matrix. We will determine whether these lesions in the DNA replicative process in heated cells result in the long-term presence of DNA strand breaks in DNA replicated during cell heating and thus ultimately to chromosome aberration formation and cytotoxicity.