CELL CYCLE CONTROL IN EARLY DROSOPHILA DEVELOPMENT

在多细胞生物中，DNA复制的调控是至关重要的 为他们的发展。 此外，DNA的不当调节 复制可导致疾病状态如恶性肿瘤或细胞死亡。 本提案中的实验涉及发展的两个方面 DNA复制的调控。 最早的控件之一， 发育是胚胎中DNA复制的重新启动， 到受精。 在大多数生物体中， 在一些细胞中发生改变，使得S期与 有丝分裂和细胞分裂，导致DNA含量的增加， 细胞（polyteny或polyploidy）。 的这两个方面 DNA复制的发育调控将在 果蝇，黑腹果蝇，因为突变可以被分离出来， 哪种DNA复制受到了不恰当的控制 两个基因已被确定，钚（plu）和盘古（png）， 在发育开始时调节DNA复制。 未受精卵 这些基因中的任何一个突变体都不适当地经历了大量的DNA 复制;此外，所有四种减数分裂产物中的DNA似乎 复制而不仅仅是原核。 plu和png的分析 将是理解休眠卵母细胞如何转化为 发育中的胚胎对成熟和受精信号的反应。 plu和png调控早期DNA复制的机制 发展将阐明实验，将确定是否 它们控制进入S期或者是否调节DNA复制 在S期，可能通过阻断再起始。 产品编码 通过克隆plu和png基因来鉴定， 将确定它们的蜂窝位置。 发展表达 的基因将被解决，特别是基因产物是否 在受精后发生了改变。 plu，png和 另外四个基因调控着最早期的细胞发育周期 将通过遗传和分子方法进行研究。 果蝇的多伸化是由于细胞周期的改变， 细胞周期，其中S期与间隙期交替，但无有丝分裂 发生。 内细胞周期处于发育控制之下， 多线化的发生与精确的时间和空间 在胚胎发育的后半期调控。 调控基因 在发育过程中触发多伸化的发生， 将鉴定和分析endo细胞周期。 候选 调控基因已被分离的标准，他们是 在几个细胞中， 胚胎中的组织。 这些基因的突变对 将被确定，那些被证明是调节 这个过程将被克隆。 将对突变体进行选择， 影响了多伸化。

The regulation of DNA replication in multicellular organisms is critical for their development. In addition, the improper regulation of DNA replication can lead to disease states such as malignancy or cell death. The experiments in this proposal address two aspects of the developmental regulation of DNA replication. One of the earliest controls in development is the restart of DNA replication in the embryo in response to fertilization. In most organisms the control of DNA replication in altered in some of the cells such that S phase becomes unlinked from mitosis and cell division, leading to an increase in the DNA content of the cell (polyteny or polyploidy). These two aspects of the developmental regulation of DNA replication will be investigated in the fruit fly, Drosophila melanogaster, because mutations can be isolated in which DNA replication is improperly controlled. Two genes have been identified, plutonium (plu) and pan gu (png), that regulate DNA replication at the onset of development. Unfertilized eggs mutant in either of these genes inappropriately undergo extensive DNA replication; moreover, the DNA in all four meiotic products appears to replicate rather than simply the pronucleus. Analysis of plu and png will be key to understanding how a resting oocyte is converted into a developing embryo in response to maturation and fertilization signals. The mechanisms by which plu and png regulate DNA replication in early development will be elucidated by experiments that will determine whether they control entry into S phase or whether they regulate DNA replication within S phase, possibly by blocking reinitiation. The products encoded by the plu and png genes will be identified by cloning the genes, and their cellular location will be determined. The developmental expression of the genes will be addressed, particularly whether the gene products are altered after fertilization. The interaction between plu, png, and four other genes that regulate the earliest cell cycles of development will be investigated by genetic and molecular approaches. Polytenization in Drosophila results from a modified cell cycle, the endo cell cycle, in which S phase alternates with a gap phase, but no mitosis occurs. The endo cell cycle is under developmental control because the onset of polytenization occurs with precise temporal and spatial regulation during the latter half of embryogenesis. Regulatory genes that trigger the onset of polytenization in development or that control the endo cell cycle will be identified and analyzed. Candidate regulatory genes have been isolated by the criteria that they are transcriptionally activated at the onset of polytenization in several tissues in the embryo. The effect of mutation of these genes on polytenization will be determined, and those that are shown to regulate this process will be cloned. A selection will be done for mutants in which polytenization is affected.