REGULATION OF THE ENDO CELL CYCLE IN DROSOPHILA

果蝇内细胞周期的调节

• 批准号: 6519908
• 负责人: Terry L. ORR-WEAVER
• 金额: $ 26.51万
• 依托单位: WHITEHEAD INSTITUTE FOR BIOMEDICAL RES
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-05-01 至 2003-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6519908
• 关键词: DNA replication; Drosophilidae; acetylation; alleles; cell cycle; cell growth regulation; cyclins; egg /ovum; gel mobility shift assay; gene expression; gene interaction; gene mutation; genetic manipulation; genetic polymorphism; genetic regulation; histones; immunofluorescence technique; immunoprecipitation; molecular cloning; natural gene amplification; nucleic acid sequence; transcription factor

Cell division must be regulated precisely, because when this regulation fails uncontrolled division and cancer ensue. During the development of multicellular organisms cell growth and division have to be coordinated with developmental signals. In addition to exit from the cell cycle to permit differentiation, a variety of cell cycle variants are utilized throughout the plant and animal kingdoms. One of these modified cell cycles, the endo cell cycle, results in DNA replication in the absence of mitosis and produces the polyploid or polytene cells that are found in at least some tissues in almost all organisms. This proposal addresses the three key aspects of how the endo cycle is regulated, using Drosophila as a model. The most significant distinction between the endo cycle and the mitotic cycle is the absence of mitosis. The morula gene is required to inhibit mitosis in the endo cycle. The MORULA protein will be identified and the mechanism by which it blocks mitosis determined. A second difference between the two cell cycles is that DNA replication is differentially regulated in the endo cycle such that some genomic regions are underreplicated while others are overreplicated and the genes amplified. Mutations in the two subunits of the E2F transcription factor, dDP and dE2F, affect differential replication during polyploid S phase. These results reveal a previously unrecognized role for E2F in controlling DNA replication once S phase has initiated. It will be determined whether E2F affects DNA replication via one of its transcriptional targets or whether it has a more direct effect on replication origins. Because the regulatory hierarchy that controls E2F activity is mutated in most human tumors, it is significant for understanding the causes of caner to determine how E2F influences DNA replication. The third level of regulation is common to both the endo cell cycle and the mitotic cycle: the transcripts that are induced at the G1-S transition must be downregulated after DNA replication has initiated in order for a subsequent round of replication to occur. The l(2)52Ec gene is unusual in being necessary both for DNA replication and downregulation of G1-S transcripts, suggesting it is a prerequisite for the cell to recognize that replication has initiated. The hypothesis that the l(2)51Ec protein is a component of the origin complex and necessary for downregulation of previously induced genes will be tested.

必须精确调节细胞分裂，因为当该调节失败时，不受控制的分裂并随之而来。 在多细胞生物的发育过程中，细胞生长和分裂必须与发育信号协调。 除了从细胞周期退出以允许分化外，在整个动植物界都使用了多种细胞周期变体。 这些修饰的细胞周期之一，即Endo细胞周期，在没有有丝分裂的情况下导致DNA复制，并产生几乎所有生物体中至少在某些组织中发现的多倍体或多型细胞。 该建议探讨了使用果蝇作为模型来调节内部周期的三个关键方面。 内部周期和有丝分裂周期之间最显着的区别是缺乏有丝分裂。 需要毛拉基因在内部周期抑制有丝分裂。 将鉴定莫拉蛋白，并确定其阻断有丝分裂的机制。 两个细胞周期之间的第二个区别在于，DNA复制在内部循环中受到差异调节，使得某些基因组区域被不足，而其他基因被过度复制并扩增基因。 E2F转录因子DDP和DE2F的两个亚基的突变会影响多倍体S相期间的差异复制。 这些结果表明，一旦S相开始，E2F先前无法识别的作用在控制DNA复制方面。 将确定E2F是否通过其转录目标之一影响DNA复制，还是对复制起源有更直接的影响。 由于控制E2F活性的调节层次结构在大多数人类肿瘤中被突变，因此对于理解Caner的原因是确定E2F如何影响DNA复制的原因。 第三级的调节级别对于Endo细胞周期和有丝分裂循环都是共同的：在DNA复制后必须下调在G1-S转变处诱导的转录本，以便发生随后的复制。 L（2）52EC基因对于G1-S转录本的DNA复制和下调都是不寻常的，这表明它是细胞识别复制已启动的先决条件。 L（2）51EC蛋白是原点复合物的组成部分，并且将测试以前诱导的基因的下调所必需的假设。