The DNA damage response of fast-cycling erythroblasts

项目摘要红细胞生成，或红细胞形成的过程，在一生中都是持续的。它的 研究有助于阐明红系疾病，最明显的是贫血，占所有残疾的8.8% 全球范围内。它也是研究发育生物学基本问题的一个可访问的模型。这 这一建议是基于最近的发现，即一个关键的红系细胞命运决定与戏剧性的 缩短S时相。在一些其他发育系统中，细胞命运的决定同样与一种 更快的S阶段。更快的S阶段可能是以基因组不稳定为代价完成的，就像癌基因- 诱导复制应激。然而，对生理上较快的S阶段与其关系的研究 正常发育过程中缺乏DNA损伤反应。这个项目的目标是确定 红系发育转换的S阶段异常快，导致DNA复制保真度和/或改变 DNA损伤反应的改变。 早期的红系祖细胞被称为“集落形成单位红系”(CFU-e)，经历了几个自我更新的细胞 在过渡到红系终末分化(ETD)之前的分裂，在那里它们开始表达红细胞 基因。从自我更新的CFU-e祖细胞向成熟的ETD红细胞的转变是一个快速的过程 与单细胞周期同步并依赖于单细胞周期S期的转录开关。令人惊讶的是， S阶段的cfu-e/eTD开关的持续时间非常短，仅持续4小时，而 在cfu-e周期之前，由于复制分叉速度在全球范围内提高了50%。这些变化 在S阶段，cfu-e/eTD开关需要速度；cfu-e祖细胞较慢的S阶段促进 ETD早期的快速S期促进红系基因的诱导。这可能是意料之中的 早期ETD红细胞的快速S阶段将导致复制分叉失速事件的增加 (‘复制压力’)和增加的基因组不稳定性。我们的实验目的是检验两个对立的，但不是 必然互斥的假设： 假设1：早期ETD的较快的S阶段是以较低质量的复制为代价的。 假设2：早期ETD的S阶段较快，反映了复制偶联的DNA修复“增压”。 目的1分析快速周期早期ETD红细胞DNA复制的质量。目标2将决定 快周期ETD红细胞与慢周期CFU的DNA损伤反应有何不同-- E前体物。目的3将确定较快的S时相和早期改变的DNA损伤反应 ETD在基因上是可分离的。

Project Summary Erythropoiesis, or the process of red cell formation, is continuous throughout life. Its study helps elucidate erythroid disorders, most notably anemia, which accounts for 8.8% of all disability globally. It is also an accessible model for studying fundamental questions in developmental biology. This proposal is based on recent finding that a key erythroid cell fate decision is associated with dramatic shortening of S phase. Cell fate decisions in some other developmental systems are similarly associated with a faster S phase. A faster S phase might be accomplished at the cost of genomic instability, as in oncogene- induced replicative stress. However, studies of the relationships between a physiologically faster S phase and the DNA damage response in normal development are lacking. This project’s goal is to determine whether the unusually fast S phase of the erythroid developmental switch entails altered DNA replication fidelity and/or alterations in the DNA damage response. Early erythroid progenitors, termed ‘colony-forming-unit-erythroid’ (CFU-e), undergo several self-renewal cell divisions before transitioning into Erythroid Terminal Differentiation (ETD), where they begin to express red cell genes. The transition from self-renewing CFU-e progenitors to maturing ETD erythroblasts is a rapid transcriptional switch that is synchronized with, and dependent on, a single cell cycle S phase. Strikingly, the S-phase of the CFU-e/ETD switch is of uniquely short duration, lasting only 4 hr, compared with 7 hr in preceding CFU-e cycles, as a result of a global, 50% increase in the speed of replication forks. These changes in S phase speed are required for the CFU-e/ETD switch; the slower S phase of CFU-e progenitors promotes their self-renewal, while the fast S phase of early ETD promotes erythroid gene induction. It might be expected that the fast S phase of early ETD erythroblasts would exact a ‘cost’ of increased replication fork stalling events (‘replication stress’) and increased genomic instability. our experimental AIMS test two opposing but not necessarily mutually exclusive hypotheses: Hypothesis 1: The faster S phase of early ETD is achieved at a cost of lower quality replication. Hypothesis 2: The faster S phase of early ETD reflects “supercharged” replication-coupled DNA repair. AIM 1 will analyze the quality of DNA replication in fast-cycling early ETD erythroblasts. AIM 2 will determine how the DNA damage response of fast-cycling ETD erythroblasts differs from that of their slower-cycling CFU- e precursors. AIM 3 will determine whether the faster S phase and the altered DNA damage response of early ETD are genetically separable.