REGULATION AND FUNCTION OF A HUMAN EMBRYONIC GLOBIN

人的表珠蛋白是一种类似β的珠蛋白，其表达仅限于胚胎卵黄囊血岛中的原始红细胞。与胎儿和成人珠蛋白不同，表珠蛋白基因调控的机制基础及其编码蛋白的功能知之甚少。虽然转录下调是胚胎珠蛋白基因沉默的主要影响因素，但最近的研究表明，其他转录后事件也在这一过程中发挥了以前没有预料到的重要作用。无论是具体的转录后机制涉及，还是他们的最终贡献，以表珠蛋白的调控尚未确定。同样，由表珠蛋白亚基组装而成的血红蛋白的生理特性也没有被完全描述。充分定义epsilon珠蛋白的分子控制和功能的重要性因其重新激活的表达可能对具有β-珠蛋白表达遗传缺陷的成年人的治疗有益而被放大。如果不全面了解epsilon-珠蛋白的调节和功能，就无法判断该方法的可行性和临床潜力，目前的提案将提供这一点。首先，将确定血红蛋白的关键生理重要性质，这些血红蛋白将聚集在表达表珠蛋白的最终红细胞中。这些研究将在体外和转基因小鼠中进行，将包括测定Hbα2epsilon2的O2亲和力和抗镰刀特性，这对患有β地中海贫血和镰状细胞性贫血的人特别重要。其次，将建立特定的转录后机制对确定的红细胞中epsilon珠蛋白表达的影响。已知将被研究的特定过程(信使核糖核酸稳定性、信使核糖核酸翻译效率和珠蛋白亚基稳定性等)会影响其他人类珠蛋白的表达。作为一个整体，这些研究将开始使已知的胚胎表观珠蛋白与其他胎儿和成人珠蛋白的已知水平持平。此外，这些研究提供的信息将允许一种合理的方法来设计旨在重新激活epsilon-珠蛋白的分子疗法，以及对这种方法将在治疗上有益的可能性的知情预期。

Human epsilon-globin is a beta-like globin whose expression is developmentally restricted to primitive erythroblasts in the blood islands of the embryonic yolk sac. In contrast to fetal and adult globins, the mechanistic bases for epsilon-globin gene regulation and the function of its encoded protein are poorly understood. Although transcriptional downregulation is a major effector of embryonic globin gene silencing, recent studies indicate that other, post-transcriptional events also play an important and previously unanticipated role in this process. Neither the specific post-transcriptional mechanisms involved, nor their ultimate contribution to epsilon-globin regulation have been established. Likewise, the physiologic properties of hemoglobins assembling from epsilon-globin subunits are incompletely described. The importance of fully defining the molecular controls and function of epsilon globin is magnified by the possibility that its reactivated expression might be therapeutically beneficial to adults with genetic defects in beta-globin expression. The feasibility and clinical potential of this approach cannot be judged without a comprehensive understanding of epsilon-globin regulation and function, which the current proposal will provide. First, key physiologically-important properties will be determined for hemoglobins that will assemble in definitive erythrocytes expressing epsilon globin. These studies, which will be done both in vitro and in transgenic mice, will include determinations of the O2 affinity and the anti-sickling characteristics of Hb alpha2epsilon2, of particular importance to individuals with beta thalassemia and sickle cell anemia. Second, the effect of specific post-transcriptional mechanisms on the expression of epsilon globin in definitive erythrocytes will be established. The specific processes that will be studied (mRNA stability, mRNA translational efficiency, and globin subunit stability, among others) are known to affect the expression of other human globins. As a group, these studies will begin to bring what is known about embryonic epsilon globin into parity with what is known about other fetal and adult globins. Moreover, the information provided by these studies will permit a reasoned approach to the design of molecular therapies aimed at epsilon-globin reactivation as well as an informed expectation of the likelihood that such an approach will be therapeutically beneficial.