Mechanisms of Nuclear and Cell Fusion in Yeast

酵母细胞核和细胞融合机制

• 批准号: 7931509
• 负责人: Mark David Rose
• 金额: $ 10万
• 依托单位: PRINCETON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-30 至 2011-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7931509
• 关键词: Address; Animal Model; B-Lymphocytes; Behavior; Biological; Biology; Cell Cycle; Cell Cycle Completion; Cell Nucleus; Cell division; Cell fusion; Cell physiology; Cells; Cellular biology; Complex; Couples; Coupling; Defect; Development; Diploid Cells; Diploidy; Disease; Down-Regulation; Endocytosis; Event; Face; Fertility; Fertilization; Gene Expression; Gene Proteins; Genes; Germ Cells; Goals; Haploidy; Homologous Gene; Human; Malignant Neoplasms; Membrane; Membrane Fusion; Methods; Mitosis; Mitotic; Mutation; Nuclear; Nuclear Envelope; Nuclear Export; Nuclear Fusion; Nuclear Inner Membrane; Organism; Partner in relationship; Pathway interactions; Pheromone; Play; Process; Proteins; Recruitment Activity; Regulation; Reproduction; Role; Saccharomyces cerevisiae; System; Testing; Toxic effect; Undifferentiated; Yeasts; amphiphysin; base; functional genomics; novel; premature; prevent; public health relevance; rho; rho GTP-Binding Proteins; yeast protein; zygote

DESCRIPTION (provided by applicant): Our long-term objectives are to define the pathway by which two haploid yeast cells fuse to become one diploid cell. Related to fertilization, conjugation is a fundamental process common to all sexually reproducing organisms. Conjugation also has close parallels to cell fusion events during development. We propose to continue our analysis of genes required for two major steps in conjugation, cell fusion and nuclear envelope fusion. Many of the genes required for cell and nuclear fusion have homologs in all eukaryotic organisms and their study will provide important clues to human cell biology, fertility and disease. During development of multicellular organisms, cells transition from a proliferative state, devoted to cell division and lacking specialized functions, to a differentiated state, in which cell division ceases and specialized cell functions are expressed. Proliferation and differentiation are mutually exclusive states, and orderly development requires that cells shut down mitotic functions as they turn on the specialized functions related to differentiation. Indeed one hallmark of cancer is that cells tend to lose differentiated functions as they re- acquire the capacity for unrestrained proliferation. Thus the coordination of mitosis and differentiation is of vital importance. Similarly, when yeast cells conjugate, they must exit the cell cycle and express proteins required for cell and nuclear fusion. However, because gene expression begins before the completion of the previous cell cycle, and because several proteins required for conjugation have other mitotic functions, yeast cells face the additional challenge of having to prevent premature activation of conjugation. The major goal of this project is to identify the specific effects of premature activation of mating functions, and identify the genes/proteins that are toxic when prematurely activated. As a specific example, we aim to understand the controls governing a key regulator of cell fusion, Fus2p, whose localization is under extraordinarily complex regulation by both the cell cycle and conjugation. Fus2p's regulation therefore serves as a central paradigm for the transition between mitosis and conjugation. We hypothesize that the regulation of Fus2p localization prevents interference with cell-cycle completion, which we will test this by identifying the downstream pathways regulated by Fus2p. We will examine the behavior of other key proteins co-opted during mating to determine if regulated localization is a general mechanism to prevent cell-cycle interference,. At the culmination of conjugation, the two nuclear envelopes fuse to create a single diploid nucleus. Because the nuclear envelope is composed of two membranes, two distinct fusion events occur in a coordinated fashion, and fusion of the inner membranes must be catalyzed by as yet unknown proteins. We hypothesize that Kar5p, a novel conjugation-induced protein, couples the inner and outer nuclear envelopes during fusion and facilitates inner-membrane fusion. Nuclear envelope fusion may be excellent paradigm for ER remodeling, an example of a critical mitotic process co-opted to serve a different function during conjugation. Public Health Relevance: As organisms grow and develop their cells transition from proliferation, when they are dividing, but lack specialized functions, to differentiation, when cell division stops and they acquire specialized functions. Successful development requires that cells not turn on the specialized functions while they are trying divide; one hallmark of cancer is that cells lose their specialized functions as they regain the capacity for unrestrained division. This project addresses the same problem in a model organism, baker's yeast, which carefully regulates the transition from cell division to being able to mate, using genes similar to human genes with relevance to human cell biology, fertility and disease.

描述（由申请人提供）：我们的长期目标是确定两个单倍体酵母细胞融合成为一个二倍体细胞的途径。与受精相关，接合是所有有性生殖生物体共有的基本过程。接合也与发育过程中的细胞融合事件非常相似。我们建议继续分析接合中两个主要步骤（细胞融合和核膜融合）所需的基因。细胞和核融合所需的许多基因在所有真核生物中都有同源物，它们的研究将为人类细胞生物学、生育力和疾病提供重要线索。在多细胞生物的发育过程中，细胞从致力于细胞分裂且缺乏专门功能的增殖状态转变为细胞分裂停止并表达专门细胞功能的分化状态。增殖和分化是相互排斥的状态，有序的发育要求细胞在开启与分化相关的专门功能时关闭有丝分裂功能。事实上，癌症的一个标志是细胞在重新获得不受限制的增殖能力时往往会失去分化的功能。因此，有丝分裂和分化的协调至关重要。同样，当酵母细胞结合时，它们必须退出细胞周期并表达细胞和核融合所需的蛋白质。然而，由于基因表达在前一个细胞周期完成之前开始，并且由于接合所需的几种蛋白质具有其他有丝分裂功能，因此酵母细胞面临着必须防止接合过早激活的额外挑战。该项目的主要目标是确定交配功能过早激活的具体影响，并确定过早激活时有毒的基因/蛋白质。作为一个具体的例子，我们的目标是了解控制细胞融合关键调节因子 Fus2p 的控制，其定位受到细胞周期和接合的极其复杂的调节。因此，Fus2p 的调节充当有丝分裂和接合之间转变的中心范例。我们假设 Fus2p 定位的调节可以防止干扰细胞周期的完成，我们将通过识别 Fus2p 调节的下游途径来测试这一点。我们将检查交配过程中选择的其他关键蛋白质的行为，以确定调节定位是否是防止细胞周期干扰的通用机制。在接合达到顶峰时，两个核膜融合形成一个二倍体核。由于核膜由两层膜组成，因此两个不同的融合事件以协调的方式发生，并且内膜的融合必须由迄今未知的蛋白质催化。我们假设 Kar5p 是一种新型缀合诱导蛋白，在融合过程中偶联内外核膜并促进内膜融合。核膜融合可能是内质网重塑的绝佳范例，这是在接合过程中选择发挥不同功能的关键有丝分裂过程的一个例子。公共健康相关性：随着生物体的生长和发育，其细胞从增殖（细胞分裂但缺乏专门功能）转变为分化（细胞分裂停止并获得专门功能）。成功的发育要求细胞在尝试分裂时不启动特殊功能；癌症的标志之一是细胞在恢复不受限制分裂的能力时失去其特殊功能。该项目解决了模型生物体面包酵母中的相同问题，该酵母利用与人类细胞生物学、生育力和疾病相关的与人类基因相似的基因，仔细调节从细胞分裂到能够交配的转变。