Factors modulating gamma globin gene expression

改善镰状细胞病与持续胎儿血红蛋白表达表明，治疗能够重新激活γ-珠蛋白gone表达应探讨。能够逆转成人红系细胞中γ-至β-珠蛋白转换的转录因子的基因转移代表了治疗这种破坏性疾病的一种方法。我们 已经确定了一种蛋白质复合物，阶段选择蛋白（SSP），这是一个强有力的候选人，这种方法。SSP由普遍存在的转录因子CP 2/LBP-1a、红系限制性组分p22 NF-E4和稳定其他两者之间相互作用的伴侣蛋白ALY组成。我们已经证明，p22 NF-E4的功能作为γ-基因表达的激活剂，并在胎儿/成人基因竞争的设置促进成人β-基因表达的伴随下调。在betaYAC转基因小鼠中p22 NF-E4的强制表达延迟了胎儿/成人转换，但不能推翻控制γ基因沉默的内在机制。我们已经表明，SSP的功能是介导的直接蛋白质/蛋白质相互作用与辅激活因子和一般的转录因子。基于这些发现，我们假设SSP的作用，在招聘的基因座控制区（LCR）的γ-启动子通过改变这些元素的结合因子。在具体目标1中，我们将在胎儿红细胞生成的细胞和动物模型中建立与LCR和γ启动子相关的转录因子模式，并检查在这些背景下p22 NF-E4表达增加的影响。我们将确定LCR和γ-启动子在胎儿红系细胞中是否在物理上接近，以及是否受到SSP复合物的影响。在具体目标2中，我们将剖析SSP的各个组分对复合物整体功能的相对贡献，包括它们在因子结合和LCR/启动子相互作用中的作用。具体目标3将集中在LCR/γ-启动子相互作用和因子占用的突变，破坏内在的γ-基因沉默的设置，并在这种情况下的p22 NF-E4表达的影响。总之，这些研究将确定SSP复合物在修饰因子与LCR和γ-启动子的结合中的作用，并确定SSP的主要功能是否是直接将LCR募集到启动子。最终，它们可能为镰状细胞病提供新的治疗策略。

Amelioration in sickle cell disease seen with persistent fetal hemoglobin expression suggests that therapies capable of reactivating gamma-globin gone expression should be explored. Gene transfer of a transcription factor capable of reversing the gamma- to beta-globin switch in adult erythroid cells represents one approach to treatment of this devastating disorder. We have identified a protein complex, the stage selector protein (SSP) that is a strong candidate for this approach. The SSP consists of the ubiquitous transcription factor CP2/LBP-1a, p22NF-E4, an erythroid-restricted component, and ALY, a chaperone protein that stabilizes the interaction between the other two. We have demonstrated that p22 NF-E4 functions as an activator of gamma-gene expression, and in the setting of fetal/adult gene competition promotes a concomitant down-regulation of adult beta-gene expression. Enforced expression of p22NF-E4 in betaYAC transgenic mice delayed the fetal/adult switch but was unable to override the intrinsic mechanisms that govern gamma-gene silencing. We have shown that the function of the SSP is mediated by direct protein/protein interactions with co-activators and general transcription factors. Based on these findings, we postulate a role for SSP in recruiting the locus control region (LCR) to the gamma-promoter through changes in factor binding to these elements. In Specific Aim 1, we will estabh'sh the pattern of transcription factor association with the LCR and gamma-promoter in cellular and animal models of fetal erythropoiesis and examine the effects of increased expression of p22 NF-E4 in these contexts. We will determine whether the LCR and gamma-promoter are in close physical proximity in fetal erythroid cells and if this is influencedby the SSP complex. In Specific Aim 2, we will dissect the relative contribution of the individual components of the SSP to the overall function of the complex, including their role in factor binding and LCR/promoter interaction. Specific Aim 3 will focus on LCR/gamma-promoter interactions and factor occupancy in the setting of a mutation that disrupts intrinsic gamma-gene silencing, and the effects of p22NF-E4 expression in this context. In summary, these studies will define the role of the SSP complex in modifying factor association with the LCR and gamma-promoter, and determine whether the predominant function of the SSP is to directly recruit the LCR to the promoter. Ultimately they may provide new therapeutic strategies for sickle cell disease.