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

了解细胞增殖的调节机制， 分化是理解多细胞分化的基础。 有机体 研究这些调节机制的一种方法是 研究转化细胞的行为。 通过使用Ad2- （非致癌）和SV40-（高致癌）转化仓鼠细胞，我们 已经鉴定了这些细胞的表型特征（例如，AD2 对非特异性免疫体外裂解的敏感性和SV40抗性 效应细胞），这些细胞与它们在肿瘤中形成肿瘤的能力相关。 免疫活性仓鼠。 我们还发现，虽然Ad2和SV40转化， 细胞在转化生长因子的生产中同样活跃，只有 SV40转化的细胞分泌一种强大的抗有丝分裂原， 宿主体内防御 我们还使用SV40来研究 病毒的问题取向。 我们发现皮下注射少量 SV40的t-抗原突变体经常诱发腹部B细胞淋巴瘤， 仓鼠，而不是由野生型诱导的皮下纤维肉瘤 SV40 突变体可能不能产生一种生长因子， 非增殖细胞的体内转化。 在另一个项目中，我们正在研究诱变的机制， 以SV40为载体的穿梭载体作为探针， DNA损伤剂诱导哺乳动物细胞突变的机制 细胞 我们对UV损伤的SV40 DNA在体内复制的研究已经导致 哺乳动物细胞复制机制的明确模型 对DNA损伤的反应，以及在复制过程中的哪些步骤 突变就不可逆转地形成了。 通过使用航天飞机 载体，我们已经广泛地描述了发生突变的类型， 在哺乳动物细胞中自发地或响应于DNA损伤。 对这些突变的序列特异性的分析导致了一个模型 这就解释了哺乳动物DNA聚合酶如何在 DNA合成导致突变 进一步的研究与载体在一个 体外DNA复制系统应允许与体内 我们观察到的复制缺陷。

Understanding the mechanisms of regulation of cellular proliferation and differentiation is basic to understanding development of multicellular organisms. One approach to investigating these regulatory mechanisms is to study the behavior of transformed cells. Through the use of Ad2- (non-oncogenic) and SV40- (highly oncogenic) transformed hamster cells, we have identified the phenotypic characteristics of these cells (e.g., Ad2 sensitivity and SV40 resistance to in vitro lysis by non-specific immune effector cells) that correlate with their ability to form tumors in immunocompetent hamsters. We also find that while Ad2-and SV40-transformed cells are equally active in production of transforming growth factors, only SV40-transformed cells secrete a powerful anti-mitogen, which may inhibit host defenses in vivo. We are also using SV40 to study the genetic basis of viral issue tropism. We find that subcutaneously injected small t-antigen mutants of SV40 often induce abdominal B-cell 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. In another project, we are studying the mechanisms of mutagenesis, using an SV40-based shuttle vector as a probe to investigate the molecular mechanisms by which agents that damage DNA induce mutations in mammalian cells. Our studies on replication of UV-damaged SV40 DNA in vivo have led to a well-defined model of how the mammalian cell replication machinery responds to DNA damage, and at what steps in the replication process mutations become irreversibly established. Through use of the 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 a model which explains how the mammalian DNA polymerase introduces errors during DNA synthesis, causing mutations. Further studies with the vector in an in vitro DNA replication system should allow a correlation with the in vivo replication defects we observed.