CELL DIFFERENTIATION AND REPAIR OF RADIATION DAMAGE

哺乳动物细胞中辐射诱导的DNA损伤的修复通常 通过使用体外生长的增殖细胞进行研究。 绝 然而，大多数原位哺乳动物细胞是有丝分裂后存在于细胞中的。 终末分化的状态。 建议的总体目标 研究是为了研究辐射诱导的DNA损伤的修复， 在分子、生化和功能水平上， 分化细胞 作为细胞分化的模型，这些 研究将集中于鼠3 T3-T前脂肪细胞系统。 在这 在体外系统中，将活跃循环的3 T3-T前脂肪细胞暴露于人 血浆导致它们终末分化为成熟脂肪细胞。 初步研究表明，3 T3-T干细胞的分化 伴随着DNA损伤修复能力的降低 由电离辐射和紫外线辐射引起。 这项建议的目的之一是 定义导致维修能力降低的机制 终末分化的3 T3-T细胞。 这些研究将包括 评估各种类型的辐射诱导的DNA损伤的修复 并研究可能影响其修复的各种参数。 在 除了这些机理研究之外，本提案的主要目标是 研究DNA修复缺陷的生物学后果， 终末分化的3 T3-T细胞。 因为需要转录 维持分化细胞的功能，RNA合成，特异性 酶活性和mRNA水平将在照射后进行评价。 DNA 降解也将被用作一个功能完整性的衡量标准， 分化细胞 本提案的最终目的是确定 分化对特定基因组序列修复的影响。 紫外线诱导的嘧啶二聚体的修复将在基因中进行分析， 在3 T3-T细胞分化期间被打开和关闭。 调查人员 这种性质被设计来确定基因表达对 DNA修复 因此，这些研究不仅应提供信息， 关于未修复的DNA损伤对后- 有丝分裂，分化的细胞，但也有助于基本的 了解DNA修复过程的调节。 此外，本发明还提供了一种方法， 这些调查应能为今后的假设提供数据 关于终末期DNA损伤之间的潜在关系， 功能性细胞和放射治疗诱导的正常组织损伤。

The repair of radiation-induces DNA damage in mammalian cells has usually been investigated by using proliferating cells grown in vitro. The vast majority of mammalian cells in situ, however, are post-mitotic existing in a state of terminal differentiation. The general aim of the proposed research is to investigate the repair of radiation-induced DNA damage on the molecular, biochemical and functional levels in terminally differentiated cells. As a model for cellular differentiation, these studies will focus on the murine 3T3-T proadipocyte cell system. In this in vitro system, exposure of actively cycling 3T3-T proadipocytes to human plasma results in their terminal differentiation into mature adipocytes. Preliminary studies indicate that the differentiation of 3T3-T stem cells into adipocytes is accompanied by a reduced capacity to repair DNA damage induced by radiation, both ionizing and UV. One aim of this proposal is to define the mechanism(s) responsible for the reduced repair capabilities of terminally differentiated 3T3-T cells. These studies will consist of evaluating the repair of the various types of radiation-induced DNA lesions and investigating various parameters that may influence their repair. In addition to these mechanistic studies, a primary goal of this proposal is to investigate the biological consequence of the DNA repair deficiency in terminally differentiated 3T3-T cells. Because transcription is required to maintain the function of differentiated cells, RNA synthesis, specific enzyme activities and mRNA levels will be evaluated after irradiation. DNA degradation will also be used as a measure of the functional integrity of a differentiated cell. The final aim of this proposal involves determining the effects of differentiation on the repair of specific genomic sequences. The repair of UV-induced pyrimidine dimers will be analyzed in genes that are turned on and off during 3T3-T cell differentiation. Investigators of this nature are designed to determine the influence of gene expression on DNA repair. Thus, these studies should not only generate information regarding the influence of unrepaired DNA damage on the function of post- mitotic, differentiated cells, but also contribute to the basic understanding of the regulation of DNA repair processes. In addition, these investigations should provide data on which to base future hypotheses regarding the potential relationship between DNA damage in endstage, functional cells and radiotherapy-induced normal tissue damage.