ALTERATION OF NAD METABOLISM BY CHEMICAL CARCINOGENS

DNA损伤的发生和细胞对DNA损伤的反应是 参与了一个项目的启动和推广阶段 致癌作用 拟议的研究将集中在机制和 聚腺苷二磷酸核糖快速变化的生物学意义 环境诱导的DNA损伤引起的代谢。 这些研究将 使用完整的培养的小鼠细胞， N-甲基-N '-硝基-N亚硝基胍（MNNG）。 聚合物的复杂性 ADP-核糖将通过使用高选择性的聚合物分离来研究。 硼酸酯亲和树脂，HPLC分子筛分级 色谱法同时测定直链和支链 内部残基和末端残基。 这些实验将使 确定每个分子的真实聚合物尺寸和支化频率， 评估非共价键重要性所需的信息 聚合物与染色质的其他组分的相互作用。 的 聚合物的周转及其在染色质组分中的分布将 通过将上述方法与体内标记方案相结合来研究 和聚（ADP-核糖）聚合酶的抑制剂。 标签方法也将 用于评估聚（ADP-核糖）的定量意义 在未受损的细胞中进行代谢。 聚腺苷二磷酸核糖的功能 在细胞从MNNG的细胞毒性作用中恢复的代谢将是 通过同步C3 H10 T1/2细胞周期进展的研究解决 流式细胞荧光法、放射自显影和ADP-核糖基化 抑制剂的 该系统也将用于进行染色质比较 旨在产生关于稳定或变化的信息 染色质结构涉及聚（ADP-核糖）和正常细胞周期 MNNG处理的细胞中的进展。 聚（ADP-核糖）的参与 在其他重要的生物反应中对DNA损伤的代谢， 将通过评价以下作用来研究C3 H10 T1/2细胞： ADP-核糖基化抑制剂和NAD水平的营养调控 诱变和恶性转化。 这些研究将利用 共细胞毒性效应将被消除或最小化的条件， 在表达期间对生长的影响被仔细监测。 的机理 聚（ADP-核糖）代谢的高温将进行研究， 评估聚（ADP-核糖）代谢在糖尿病中可能的一般作用， 将进行对环境应激的一般细胞反应。

The occurrence of DNA damage and cellular responses to DNA damage are involved in the initiation and perhaps the promotion phase of carcinogenesis. The proposed studies will focus on the mechanism and biological significance of the rapid alteration of poly(ADP-ribose) metabolism cause by environmentally induced DNA damage. These studies will utilize intact cultured mouse cells following treatment with N-methyl-N'-nitro-N nitrosoguanidine (MNNG). The complexity of polymers of ADP-ribose will be studied by isolation of polymers using highly selective boronate affinity resins, fractionation by HPLC molecular sieve chromatography and simultaneous determination of linear and branched internal residues and terminal residues. Such experiments will allow the determination of true polymer size and branching frequency per molecule, information necessary for evaluating the importance of non-covalent interactions of the polymer with other components of chromatin. The turnover of polymers and their distribution within chromatin fractions will be studied by combining the above methods with in vivo labeling protocols and inhibitors of poly(ADP-ribose) polymerase. Labeling methods will also be used to assess the quantitative significance of poly(ADP-ribose) metabolism in non-damaged cells. The function of poly(ADP-ribose) metabolism in cellular recovery from the cytotoxic effects of MNNG will be addressed by studies of cell cycle progression in synchronized C3H10T1/2 cells using flow cytofluorimetry, autoradiography and ADP-ribosylation inhibitors. This system will also be used to make chromatin comparisons designed to yield information concerning the stabilization or alterations of chromatin structure involving poly(ADP-ribose) and normal cell cycle progression in MNNG treated cells. The involvement of poly(ADP-ribose) metabolism in other important biological responses to DNA damage in C3H10T1/2 cells will be studied by evaluating the effect of ADP-ribosylation inhibitors and nutritional manipulation of NAD levels on mutagenesis and malignant transformation. Such studies will utilize conditions where co-cytotoxic effects will be eliminated or minimized and effects on growth during expression carefully monitored. The mechanism of poly(ADP-ribose) metabolism by hyperthermia will be studied and an assessment of a possible general role of poly(ADP-ribose) metabolism in a general cellular response to environmental stress will be made.