THE CYTOLOGICAL AND PHYSIOLOGICAL MODE OF AP4A ACTION

二腺苷5‘，5’‘-P1，P4-四磷酸(Ap4A)，一种形成的核苷酸 在后反应的氨基酸活化步骤中，是无处不在的 存在于细菌和动物细胞中。酶催化合成2，4-二苯基-4-甲氧基丙烷 来自ATP和某些氨基酰基腺苷的Ap4A因存在而增强 锌离子的含量。有几条证据表明可能参与了 Ap4A在细胞增殖、DNA复制、热休克等方面的作用 反应和细胞氧化。Ap4A结合蛋白，它是 与大分子形式的DNA聚合酶α有关 小牛胸腺和HeLa细胞，并与Ap4A非共价结合 亲和力和极大的底物专一性，已被分离和 特色化的。血液中的Ap4A水平相对较高 当血小板和这些Ap4A池被定量释放时 被诱导聚集在一起。我们的工作假设是Ap4A可能是一种 细菌热休克或应激反应的诱导信号 和动物细胞，以及诱导宿主的可能信号 对各种感染、损伤和其他疾病的急性期反应 对活生生的动物进行身体侮辱。LIVE的生理反应 动物可以通过血浆Ap4A水平的增加来调节，这些水平由 上述创伤所致的血小板聚集。 热休克或急性期反应表现为诱导 蛋白质组的合成(这两者中的每一组都有不同的蛋白质 现象)，这可能使单个细胞或整个动物 适应影响细胞生长或存活的外部条件。 该项目的目的是：(1)阐明 在细菌和动物细胞中合成Ap4A；(2)研究 Ap4A与DNA复制机制相互作用机制的研究 哺乳动物细胞；(3)建立动物(大鼠、 小鼠)增加血清Ap4A水平，这可能是由 以及，(4)确定Ap4A在肿瘤转移中的作用 根据最近发现的细胞Ap4A之间的相关性 细胞的新陈代谢和转移倾向，以及公认的 体内血小板聚集与肿瘤转移的关系 这些研究的长期目标是了解Ap4A 在细胞和生理水平上的作用。这一事件的意义 建议的项目是在建立一个行动的模式和机制 潜在的细胞内介质，发出细胞反应的信号 影响生长或生存的外部条件。(G)

Diadenosine 5' ,5'''-P1,P4-tetraphosphate (Ap4A), a nucleotide formed in the back reaction of the aminoacid activation step, is ubiquitously present in bacterial and animal cells. The enzyme-catalyzed synthesis of Ap4A from ATP and certain aminoacyladenylates is enhanced by the presence of Zn2+. Several lines of evidence point to possible involvement of Ap4A in aspects of cellular proliferation, DNA replication, heat shock response and cell oxidation. An Ap4A binding protein, which is associated with the high molecular weight form of DNA polymerase alpha of calf thymus and HeLa cell and which binds Ap4A noncovalently with high affinity and great substrate specificity, has been isolated and characterized. Relatively high levels of Ap4A are present in blood platelets and these Ap4A pools are quantitatively released when platelets are induced to aggregate. Our working hypothesis is that Ap4A may be a signal for the induction of the heat shock or stress response in bacterial and animal cells as well as a possible signal for the induction of the host acute phase responses to a variety of infections, injury, and other physical insults in live animals. The physiological response of live animals could be mediated by increases in plasma Ap4A levels produced by platelets' aggregation, which is induced by the above-mentioned trauma. The heat shock or acute phase response is manifested by induction of the synthesis of groups of proteins (different proteins for each of these two phenomena) which presumably enable the individual cells or the whole animal to adapt to external conditions which affect cellular growth or survival. The proposed project is designed to: (1) elucidate the mechanism of cellular Ap4A synthesis in bacterial and animal cells; (2) study the mechanism of Ap4A interaction with the DNA replicative machinery in mammalian cells; (3) establish the physiological response of animals (rats, mice) to increase in serum Ap4A levels which may be produced by thrombocytopenia; and, (4) identify the role of Ap4A in tumor metastasis in light of the recently identified correlations between cellular Ap4A metabolism and the metastatic propensity of cells, and the well-established relationship between platelets' aggregation and tumor metastases in vivo. The long term objectives of these studies are the understanding of Ap4A action at the cellular and physiological levels. The significance of the proposed project is in establishing the mode and mechanism of action of a potential intracellular mediator which signals the cellular response to external conditions affecting growth or survival. (G)