LIPOCORTINS (ANNEXINS) AND METAL-INDUCED MUTAGENESIS

描述：(改编自申请人的摘要)：重金属 Cr2+、Ni2+、Pb2+和Cd2+是环境毒物，被认为是 致癌物质。积累的证据表明，这些金属在低水平 浓度，刺激培养细胞的DNA复制，而他们 同时抑制另一种试剂造成的DNA损伤的修复过程。 因此，各种基因的突变，如癌基因和抑癌基因 可能会形成，从而导致癌症。然而，其分子机制 重金属的诱变作用仍然知之甚少。这样的突变是最多的 很可能是由于将复制机制修改为 促进容易出错的DNA合成绕过受损的碱基 未知蛋白质(S)，在存在重金属的情况下，(A)结合到 受损的DNA，(B)解开受损的DNA和/或(C)刺激容易出错的DNA 跨病变DNA合成的聚合酶。PT的实验室最近 发现纯化的脂皮质素I异四聚体，一种核蛋白，它 能够结合各种重金属，具有一些共同特征 复制蛋白A是一种单链DNA结合蛋白 对DNA新陈代谢的多个方面是必不可少的，包括修复， 重组和复制。我们假设Lipocortin I(和相关的 Ii)异四聚体通过取代Rp-A来改变复制机制 重金属的影响。使用纯化的脂皮质异构体和 易错DNA聚合酶(POL)A、B或TI经化学修饰 多核苷酸作为损坏的DNA模板，我们将执行以下操作 具体目的：(1)研究脂皮质激素与损伤DNA的结合。 重金属的存在，(2)检查受损DNA的解离 脂皮质激素在重金属存在时的作用，以及(3)研究对 PoA、B和n在脂皮质素存在下的跨损伤DNA合成 重金属。我们提议的研究将提供进一步的见解 对致癌、遗传致癌的分子机制的认识 不稳定和与形成有关的病理疾病 重金属引起的突变。

DESCRIPTION: (Adapted from the Applicant's Abstract): Heavy metals such as Cr2+, Ni2+ Pb2+ and Cd2+ are environmental toxicants, and are regarded as carcinogens. Accumulated evidences have suggested that these metals, at low concentrations, stimulate DNA replication of cultured cells, while they simultaneously inhibit repair processes of DNA damage caused by another agent. Consequently, mutations of various genes such as oncogenes and suppressor genes could be formed, thereby causing cancer. However, the molecular mechanism of mutagenesis by heavy metals remains poorly understood. Such mutations are most likely to be resulted from modification of the replication machinery to facilitate error-prone DNA synthesis bypassing the damaged bases by an unidentified protein(s) that, in the presence of heavy metals, (a) binds to damaged DNA, (b) unwinds damaged DNA and/or (c) stimulates error-prone DNA polymerases for translesion DNA synthesis. The PT's laboratory has recently discovered that purified lipocortin I heterotetramer, a nuclear protein which is capable of binding various heavy metals, shares some common features with replication protein A (RP-A), a single strand DNA binding protein (SSB) essential for multiple aspects of DNA metabolism including repair, recombination and replication. We hypothesized that lipocortin I (and related II) heterotetramer alters the replicative machinery by replacing RP-A under the influence of heavy metals. Employing purified lipocortin heterotetramers and error-prone DNA polymerase (Pol) a, B or TI with chemically modified polynucleotides as damaged DNA templates, we will perform the following specific aims: (1) to investigate binding of lipocortins to damaged DNA in the presence of heavy metals, (2) to examine unwinding of damaged DNA by lipocortins in the presence of heavy metals, and (3) to study stimulation of Pol a, B and n by lipocortins for translesion DNA synthesis in the presence of heavy metals. Our proposed research will provide further insights to understanding of the molecular mechanisms of carcinogenesis, genetic instability and pathological diseases associated with the formation of mutations by heavy metals.