EFFECT OF PHOTORADIATION THERAPY ON DNA SYNTHESIS

血卟啉衍生物（HpD）和光已被用作 有效的抗肿瘤治疗。 这种药物会导致染色体DNA 低剂量会损害哺乳动物细胞，并抑制DNA修复 在更高的剂量。 我们最近发现纯化的小牛DNA 聚合酶δ II在治疗性HpD浓度下受到抑制 （约10-6 M），不影响其他主要细胞 DNA聚合酶α和δ I。 delta形式I和II是 哺乳动物DNA聚合酶中唯一含有3'到5' 核酸外切酶，一种被认为是精确的 DNA复制与修复 我们现在建议确定 负责修复HpD对染色体损伤的酶 DNA，并确定HpD是否诱导DNA的抑制 聚合酶δ 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， 光，然后测量DNA修复在存在特定的 DNA聚合酶α、δ I、δ II、β和 γ和拓扑异构酶I和II。 预防修复 这些特定抑制剂之一的过程将表明 需要抑制酶。 暴露细胞提取物 对高剂量的HpD和光的活性将被测定 这些DNA复制和修复酶的每一种， 可以评价HpD的抑制作用。 化学性质 HpD对DNA的损伤在细胞加工前后的变化 将确定DNA修复酶。 HpD损伤DNA 将评估其作为模板的能力， 通过小牛核聚合酶α、δ I和II合成，和 在我们的实验室中，每一种都被纯化到接近同质。 的 血卟啉使DNA聚合酶失活的化学机制 德尔塔II也将被调查。 结果应澄清 HpD抑制DNA修复的机制，也应该 定义DNA聚合酶delta 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.