Regulation of Spermatocyte Transcription by Testis TAFs

睾丸 TAF 对精母细胞转录的调节

• 批准号: 7782118
• 负责人: MARGARET T FULLER
• 金额: $ 32万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-07-01 至 2013-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7782118
• 关键词: Address; Binding; Biochemical; Cell Cycle Progression; Cell Differentiation process; Cell Lineage; Cell Nucleolus; Cells; Chromatin; Complex; Deubiquitinating Enzyme; Development; Drosophila genus; Embryo; Failure; Fingers; Funding; Gametogenesis; Gene Targeting; Genes; Genetic; Genetic Screening; Genetic Transcription; Germ Cells; Germ Lines; Goals; Grant; Histones; Homeostasis; Homologous Gene; Infertility; Male Infertility; Malignant Neoplasms; Mammals; Mediator of activation protein; Meiosis; Microarray Analysis; Modeling; Mutation; Nuclear Hormone Receptors; Orphan; PRC1 Protein; Phosphotransferases; Play; Polycomb; Polymerase; Program Development; Proliferating; Promoter Regions; Prophase; Proteins; RNA Interference; Recruitment Activity; Regulation; Regulator Genes; Regulatory Pathway; Repression; Role; SAGA; Spermatids; Spermatocytes; Spermatogenesis; Spermatogonia; Staging; Stem cells; Syndrome; Testing; Testis; Tissues; Trans-Activators; Transcript; Transcription Factor TFIIA; Work; adult stem cell; cell type; cofactor; loss of function; male; man; particle; precursor cell; programs; promoter; public health relevance; transcription factor

DESCRIPTION (provided by applicant): The gene regulatory mechanisms that program cell differentiation from proliferating precursor cells are fundamentally important for development, tissue homeostasis and cancer. Using the dramatic cellular differentiation program of spermatogenesis as a model stem cell lineage, we seek to understand the unique, cell type specific transcription program initiated in the spermatocyte stage that programs cells for terminal differentiation. We discovered that testis-specific TAFs, homologs of components of the general PolII transcription machinery, turn on expression of spermatid differentiation genes, in part by counteracting silencing by the Polycomb machinery in precursor cells. The immediate next challenge is to discover how the testis TAFs act - both directly at promoters to activate robust expression of terminal differentiation genes and in the spermatocyte nucleolus by sequestering the Polycomb transcriptional silencing complex. We will test whether the tTAFs form a testis-specific SAGA-like complex that recruits a histone deubiquitinating enzyme to promoter proximal stalled polymerases, allowing elongation of target transcripts, or instead act in a TFIID-like complex with TBP. We will investigate the role of candidate cofactors that may act with the tTAFs we have identified in a pilot RNAi screen, the mediator subunit Med27 and the orphan nuclear hormone receptor Hr51. Because the tTAFs play such a key role, the mechanisms that program the exquisitely cell type and stage specific expression of the tTAFs themselves are central for understanding the developmental regulatory pathway for cell differentiation. We will investigate the role and mode of action of the BTB-Zn finger transcriptional regulator lola, required for expression of tTAFs in spermatocytes, and its binding partner the Jil1 H3S10 kinase, which is required, like lola, for proper meiotic cell cycle progression and spermatid differentiation. In addition, in a directed genetic screen, we will test candidate transcription regulators expressed at the switch from spermatogonia to spermatocyte to identify additional cofactors that act with the tTAFs and elucidate the regulatory machinery that controls tTAF expression. Our work on the mechanism of action and mode of regulation of the tTAFs in the Drosophila male germ line may provide a paradigm for understanding how development programs cell-type specific terminal differentiation by counteracting repression by the PcG at specific target genes. In addition, understanding the mode of action of the meiotic arrest genes of Drosophila may illuminate mechanisms underlying meiosis I maturation arrest infertility in man. PUBLIC HEALTH RELEVANCE: Short statement of relevance: The goal of this project is to understand the gene regulatory mechanisms that program differentiation of male gametes. In both embryonic and adult stem cell lineages, terminal differentiation genes that are repressed by the Polycomb transcriptional silencing machinery in precursor cells must be robustly activated in a cell type specific and gene- selective manner as cell differentiate. Results of our analysis of the mode of action and regulation of the testis specific TAFs of Drosophila will establish paradigms for how cell type specific alternate forms of core gene regulatory complexes act to control cell differentiation, and how these mechanisms are themselves controlled by the germ line developmental program. Because mutations in the tTAFs cause meiosis I arrest and failure of spermatid differentiation, understanding their regulation and mode of action may illuminate mechanisms underlying the male infertility syndrome meiosis I maturation arrest.

描述（由申请人提供）：细胞从增殖前体细胞分化的基因调控机制对发育、组织稳态和癌症至关重要。利用精子发生的细胞分化程序作为模型干细胞谱系，我们试图理解在精母细胞阶段启动的独特的细胞类型特异性转录程序，该程序为细胞的最终分化编程。我们发现睾丸特异性的TAFs，即一般PolII转录机制组分的同源物，在一定程度上通过抵消前体细胞中Polycomb机制的沉默来开启精细胞分化基因的表达。接下来的挑战是发现睾丸TAFs是如何起作用的——既直接作用于启动子，激活终端分化基因的强烈表达，也通过隔离Polycomb转录沉默复合物作用于精母细胞核仁。我们将测试tTAFs是否形成睾丸特异性的saga样复合体，该复合体招募组蛋白去泛素化酶来启动近端停滞聚合酶，从而允许目标转录物的延伸，或者相反，以tfiid样复合体与TBP一起起作用。我们将研究候选辅助因子的作用，这些辅助因子可能与我们在先导RNAi筛选中发现的tTAFs、中介亚基Med27和孤儿核激素受体Hr51一起起作用。由于tTAFs发挥着如此关键的作用，因此tTAFs本身精确的细胞类型和阶段特异性表达的编程机制对于理解细胞分化的发育调节途径至关重要。我们将研究BTB-Zn手指转录调节因子lola及其结合伙伴Jil1 H3S10激酶的作用和作用方式，lola是tTAFs在精母细胞中的表达所必需的，Jil1 H3S10激酶与lola一样是减数分裂细胞周期进程和精母细胞分化所必需的。此外，在定向遗传筛选中，我们将测试在从精原细胞到精母细胞的转换中表达的候选转录调节因子，以确定与tTAF一起作用的其他辅助因子，并阐明控制tTAF表达的调节机制。我们在果蝇雄性生殖系中tTAFs的作用机制和调控模式的研究可能为理解发育如何通过对抗PcG对特定靶基因的抑制来规划细胞类型特异性终末分化提供一个范例。此外，了解果蝇的减数分裂抑制基因的作用模式可能阐明人类减数分裂I成熟抑制不育的机制。