ADENOVIRUS (AD) AND SV40---MOLECULAR AND CELLULAR BIOLOGY

染色体突变是大多数遗传性疾病的根本原因。 疾病和许多发育异常。 突变也可以 导致体细胞中基因表达的改变， 导致正常分化表型的丧失， 细胞转化 我们正在研究 使用基于SV40的载体作为探针， 研究分子机制， DNA在哺乳动物细胞中诱导突变以及这些突变如何 通过细胞DNA修复过程来防止。 通过使用 pZ189穿梭载体，我们已经广泛地表征了 哺乳动物细胞中自发发生的突变， 对DNA损伤的反应。 序列特异性分析 这些突变导致了模型，解释了 哺乳动物DNA聚合酶在DNA合成过程中引入错误， 导致突变。 用载体在体外DNA中的研究 复制系统表明，细胞因素，除了 DNA聚合酶，似乎影响复制保真度。 进一步 研究应允许对这些因素进行表征， 生化水平。 我们还使用了基于SV40的穿梭载体 系统以及CAT表达载体，以评估 细胞对DNA损伤治疗的反应。 我们还使用 体外DNA修复系统，以研究DNA修复在 分子水平。 了解细胞调节的机制 增殖和分化是理解 多细胞生物的发展。 过去几 多年来，我们一直在研究一种抗突变生长因子， 由SV40转化的仓鼠细胞分泌。 这种促有丝分裂 抑制剂（Ml）强烈地抑制了细胞增殖反应， 未转化的仓鼠细胞和正常大鼠细胞， 血清有丝分裂原 Ml还抑制正常细胞的促有丝分裂反应。 用凝集素刺激仓鼠脾淋巴细胞， T细胞（伴刀豆球蛋白A）或B细胞（美洲商陆有丝分裂原）。 我们有 提出Ml可能有助于高致瘤性， 通过干扰免疫动员的SV40转化细胞 肿瘤生长部位的效应细胞。 我们还使用SV40 研究病毒组织嗜性的遗传基础。 我们发现 皮下注射SV40的小T抗原突变体通常 诱导仓鼠腹部淋巴瘤，而不是 野生型SV40诱导的皮下纤维肉瘤。 变种人 可能不能产生体内生长所需的生长因子， 非增殖细胞的转化。

Chromosomal mutations are the underlying cause of most inherited diseases and many developmental abnormalities. Mutations can also lead to alterations in gene expression in somatic cells, leading to loss of the normal differentiated phenotype and ultimately to cellular transformation. We are studying the mechanism of mutagenesis and DNA repair using SV40-based vectors as a probes to investigate the molecular mechanisms by which agents that damage DNA induce mutations in mammalian cells and how these mutations may be prevented by cellular DNA repair processes. Through use of the pZ189 shuttle vector, we have extensively characterized the types of mutations that occur in mammalian cells either spontaneously or in response to DNA damage. Analysis of the sequence specificity of these mutations has led to models which explain how the mammalian DNA polymerase introduces errors during DNA synthesis, causing mutations. Studies with the vector in in vitro DNA replication system indicate that cellular factors, in addition to DNA polymerase, appear to influence replication fidelity. Further studies should allow a characterization of these factors on the biochemical level. We are also using the SV40-based shuttle vector system as well as CAT expression vectors to assess the effects of cell wide responses to DNA-damaging treatments. We are also using in vitro DNA repair systems to investigate DNA repair at the molecular level. Understanding the mechanisms of regulation of cellular proliferation and differentiation is basic to understanding development of multicellular organisms. For the past several years, we have been studying an antimutagenic growth factor secreted by hamster cells transformed by SV40. This mitogenic inhibitor (Ml) strongly inhibits a proliferative response in untransformed hamster cells and normal rat cells stimulated with serum mitogens. Ml also inhibits a mitogenic response by normal hamster spleen lymphocytes stimulated with lectins that activate T cells (concanavalin A) or B cells (pokeweed mitogen). We have proposed that Ml might contribute to the high oncogenicity of the SV40-transformed cells by interfering with mobilization of immune effector cells at the site of tumor growth. We are also using SV40 to study the genetic basis of viral tissue tropism. We find that subcutaneously injected small t-antigen mutants of SV40 often induce abdominal lymphomas in hamsters, rather than the subcutaneous fibrosarcomas induced by wild-type SV40. The mutants may fail to produce a growth factor required for the in vivo transformation of non-proliferating cells.