The Role of RB Family Proteins in an S Phase-Dependent Erythroid Commitment Step

RB 家族蛋白在 S 相依赖性红细胞承诺步骤中的作用

• 批准号: 8446029
• 负责人: Merav Socolovsky
• 金额: $ 24.94万
• 依托单位: UNIV OF MASSACHUSETTS MED SCH WORCESTER
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-01-22 至 2014-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8446029
• 关键词: Anemia; Biology; Blood Cells; CFU-E; Cell Cycle; Cell Cycle Regulation; Cell Differentiation process; Cell division; Cell surface; Cells; Chromatin; DNA; DNA Methylation; DNA Methyltransferase; DNA Modification Methylases; Dependence; Down-Regulation; Erythrocytes; Erythroid; Erythropoiesis; Event; Family member; Fetal Liver; Figs - dietary; Gatekeeping; Gene Expression; Generations; Genes; Knockout Mice; Laboratories; Link; Locus Control Region; Mediating; Mediator of activation protein; Molecular; Mus; Phenotype; Process; Protein Family; Regulation; Retinoblastoma; Role; S Phase; S Phase Arrest; Science; Signaling Protein; Somatic Cell; TFRC gene; Testing; Transcription Repressor/Corepressor; Tumor Suppressor Proteins; Undifferentiated; Up-Regulation; Work; beta Globin; carcinogenesis; cell type; demethylation; erythroid differentiation; gene induction; gene repression; genome-wide; human GATA1 protein; leukemia; novel; progenitor; programs; promoter; self-renewal; transcription factor

DESCRIPTION (provided by applicant): The erythroid phenotype is acquired through gene induction and morphological maturation in the space of 3 to 5 'differentiation divisions'. We recently uncovered a fundamental organizational feature of fetal liver erythropoiesis, whereby a novel S phase-dependent switch controls the transition from self-renewal to differentiation divisions (Pop et al., PLoS Biology 2010). Further, this switch also triggers an unusual process of genome-wide DNA demethylation, the first known example of such a process in somatic cells (Shearstone et al., Science 2011). The S phase-dependent switch takes place at the transition from flow-cytometric "subset 0" (S0, Lin-CD71med/low) to "subset 1" (S1, Lin-CD71high) in the murine fetal liver. It comprises several erythroid commitment events, including the onset of Epo dependence, activation of the erythroid master transcriptional regulator GATA-1, and an activating chromatin reconfiguration at the beta-globin locus-control region. These events take place synchronously, during early S phase of the last generation of colony-forming-unit erythroid (CFU-e) progenitors, and are dependent on S phase progression. The S phase-dependent switch at the S0/S1 transition represents a novel, pivotal interaction between the cell cycle and differentiation programs, distinct from the well-established interaction between terminal maturation and cell-cycle exit. The mechanisms underlying the switch and the process of global DNA demethylation that it triggers are largely unknown. We identified PU.1, a transcriptional repressor of erythropoiesis, as a central regulator of this switch. We propose that PU.1 coordinates the synchronous cell cycle and differentiation events at the S0/S1 transition, through novel, antagonistic interactions between PU.1 and S phase progression. Here we propose that the tumor suppressor protein pRb, and its family members, p107 and p130, mediate the antagonistic interactions between PU.1 and S phase, and hence act as gatekeepers of the S0/S1 erythroid commitment switch. We will investigate this hypothesis with the following two aims: 1) Determine whether the S phase-dependent switch at the S0/S1 transition is dysregulated in mice deleted for one, two or three Rb family proteins or in PU.1-null mice. We will determine whether PU.1 is able to exert its dual inhibitory functions on S phase and on erythroid differentiation in mice conditionally-deleted for one, two or three of the Rb family proteins pRb, p107 or p130. Further, we will determine whether the S0/S1 transition is accelerated or becomes S phase-independent in mice deleted for PU.1 or for Rb family proteins. 2) Determine whether PU.1 and/or Rb family members interact with DNMTs and regulate global DNA methylation at the S0/S1 transition. We will ask whether global or erythroid-specific DNA demethylation takes place prematurely in S0 cells of mice deleted for PU.1 or for Rb family proteins, and whether DNMTs are directly associated with PU.1 at gene promoters. This work has the potential to uncover fundamental mechanisms of Rb and PU.1 regulation of cell cycle and differentiation, relevant to leukemia and to anemia.

描述（由申请人提供）：红系表型是通过基因诱导和3至5个“分化分裂”的形态成熟获得的。我们最近发现了胎儿肝红细胞生成的一个基本组织特征，即一种新的S相依赖开关控制着从自我更新到分化分裂的过渡（Pop等人，PLoS Biology 2010）。此外，这种开关还触发了一个不寻常的全基因组DNA去甲基化过程，这是已知的体细胞中此类过程的第一个例子（Shearstone et al., Science 2011）。S相位依赖开关发生在小鼠胎儿肝脏从流式细胞“亚群0”（S0, Lin-CD71med/low）到“亚群1”（S1, Lin-CD71high）的转变过程中。它包括几个红系承诺事件，包括Epo依赖性的开始，红系主转录调节因子GATA-1的激活，以及β -珠蛋白位点控制区染色质的激活重组。这些事件在最后一代集落形成单位红系（CFU-e）祖细胞的S期早期同步发生，并依赖于S期进展。S0/S1转换中的S相依赖开关代表了细胞周期和分化程序之间的一种新的、关键的相互作用，不同于已经建立的终端成熟和细胞周期退出之间的相互作用。开关背后的机制和它引发的整体DNA去甲基化过程在很大程度上是未知的。我们确定了PU.1，一种红细胞生成的转录抑制因子，作为这一开关的中心调节因子。我们提出，通过PU.1和S期进展之间的新型拮抗相互作用，PU.1协调了同步细胞周期和S0/S1过渡的分化事件。在这里，我们提出肿瘤抑制蛋白pRb及其家族成员p107和p130介导了PU.1和S期之间的拮抗相互作用，因此充当了S0/S1红细胞承诺开关的守门人。我们将通过以下两个目的来研究这一假设：1)确定在缺失一个、两个或三个Rb家族蛋白的小鼠或PU.1-null中，S0/S1转换的S相依赖开关是否失调