EFFECT OF PHOTORADIATION THERAPY ON DNA SYNTHESIS

血卟啉衍生物(HPD)和LIGH已被用作 有效的抗肿瘤治疗。这种药物会导致染色体DNA 低剂量对哺乳动物细胞的损伤，并抑制DNA修复 在更高的剂量。我们最近证明，纯化的小牛DNA 聚合酶DeltaII在治疗性HpD浓度下被抑制 )10-6M)，不影响其他主要细胞 DNA聚合酶α和增量I。增量I和增量II是 唯一含有3‘至5’的哺乳动物DNA聚合酶 核酸外切酶，一种被认为是精确度 DNA复制和修复。我们现在建议确定 HpD对染色体损伤的修复酶 DNA，并确定HpD是否诱导DNA抑制 聚合酶增量II负责抑制这种修复。我们 将中国仓鼠卵巢细胞暴露于低剂量的HPD和 光，然后在特定的存在下测量DNA修复 DNA聚合酶抑制剂α、增量I、增量II、β和 和拓扑异构酶I和II.修复的预防 这些特定抑制剂中的一种进行的过程将表明 对抑制酶的要求。暴露的细胞提取液 到更高剂量的HPD和LIGH将被检测出活性 这些DNA复制和修复酶中的每一个 可以评价HpD的抑制作用。化学性质 细胞处理前后HpD对DNA损伤的研究 DNA修复酶将被确定。血色素脱氢酶对DNA的损伤 将评估其作为模板的能力 小牛核聚合酶，α，增量I和II，和 在我们的实验室中，每个都纯化到近乎均一的水平。这个 HpD失活DNA聚合酶的化学机制 Delta II也将接受调查。结果应该会澄清 HpD抑制DNA修复的机制，也应该 确定DNA聚合酶德尔塔II的生物学作用。

Hematoporphyrin derivative (HpD) and light have been used as an effective antitumor therapy. The drug causes chromosomal DNA damage in mammalian cells at low doses, and inhibits DNA repair at higher doses. We have recently shown that purified calf DNA polymerase delta II is inhibited at therapeutic HpD concentrations (approx. 10-6 M), which do not affect the other major cellular DNA polymerases alpha and delta I. The delta forms I and II are the only mammalian DNA polymerases that contain a 3' to 5' exonuclease, an activity thought to be necessary for accurate DNA replication and repair. We now propose to identify the enzymes responsible for repair of HpD damage to chromosomal DNA, and to determine whether HpD induced inhibition of DNA polymerase delta II is responsible for inhibition of this repair. We will expose Chinese hamster ovary cells to low doses of HpD and light, and then measure DNA repair in the presence of specific inhibitors of DNA polymerases alpha, delta I, delta II, beta and gamma, and topoisomerases I and II. Prevention of repair processes by one of these specific inhibitors will indicate a requirement for the inhibited enzyme. Extracts of cells exposed to higher doses of HpD and light will be assayed for the activities of each of these DNA replication and repair enzymes so that the inhibitory effects of HpD can be evaluated. The chemical nature of HpD damage to DNA before and after processing by cellular DNA repair enzymes will be determined. DNA damaged by HpD will be evaluated for its ability to serve as a template for synthesis by calf nuclear polymerases, alpha, delta I and II, and beta, each purified to near homogeneity in our laboratory. The chemical mechanism by which HpD inactivates DNA polymerase delta II will also be investigated. Results should clarify the mechanism by which HpD inhibits DNA repair, and should also define the biological role of DNA polymerase delta II.