Alpha-Globin expression: Post transcriptional mechanisms

珠蛋白mRNA的高水平稳定性是血红蛋白合成和红细胞增殖的主要决定因素。 功能红系分化过程中珠蛋白mRNA选择性稳定的基础仍然是 不太了解。我们的实验室正在使用人类α-珠蛋白mRNA作为研究这个问题的模型。 在本资助期内进行的遗传、生化和体内表达研究表明， 序列特异性3 'UTR RNA-蛋白（RNP）复合物（“c_complex”）在稳定ct- 珠蛋白mRNA。通过突变富含C的结合基序或通过阻断C-结合基序来灭活C_-复合物。 ctCP蛋白的结合导致α-珠蛋白mRNA稳定性的逐渐丧失。这种稳定性的丧失 可以通过人工将ctCP连接到3 'UTR而完全恢复。c-CP广泛分布于组织中， 这表明α-复合物的红细胞限制作用是由对c_CP或 到RNP组件的交互。主要的ctCP同种型差异性地定位于细胞核中， 细胞质有证据表明etCP在α-珠蛋白mRNA稳定中的细胞质作用是 由参与增强c_珠蛋白mRNA加工的单独的核功能补充。的 人c_-珠蛋白mRNA选择性稳定化途径及其相互关系 本文将探讨aCP在c_-珠蛋白基因表达中的核和胞质功能， 问题研究 艾姆岛鉴定在介导α-珠蛋白mRNA稳定的复合物处的相互作用。 Aim II.定义_-珠蛋白mRNA稳定化的机制以及α-珠蛋白mRNA如何 避免红细胞的衰变。 Aim III.确定ctCP如何增强ct-珠蛋白转录本的核加工，以及这些转录本如何 核事件与aCP介导的细胞质控制整合。 这些研究将扩展我们先前在ct-珠蛋白基因表达方面的工作， mRNA衰变，并建立协调核和细胞质转录后控制的范例 在红细胞基因表达中。

High-level stability of globin mRNAs is a major determinant of hemoglobin synthesis and erythrocyte function. The basis for selective stabilization of globin mRNAs during erythroid differentiation remains poorly understood. Our laboratory is using human ot-globin mRNA as a model for the study of this problem. Genetic, biochemical, and in vivo expression studies carried out over the present funding period point to a central role for a sequence-specific 3'UTR RNA-protein (RNP) complex ('c_ complex') in stabilizing ct- globin mRNA. Inactivation of the c_-complex by mutation of the C-rich binding motif or by blocking the binding of the ctCP protein results in an incremental loss of ot-globin mRNA stability. This loss of stability can be fully restored by artificially tethering ctCP to the 3'UTR. c_CPs are broadly distributed in tissues, suggesting that an erythroid- restricted role of the a-complex is dictated by specific modifications to c_CP or to interacting RNP components. The major ctCP isoforms are differentially localized in the nucleus and cytoplasm. Evidence suggests that the cytoplasmic role of etCPs in ct-globin mRNA stabilization is complemented by separate nuclear function(s) involved in enhancement of c_-globin mRNA processing. The pathways involved in selective stabilization of human c_-globin mRNA and the interrelationships between nuclear and cytoplasmic functions of aCPs in c_-globin gene expression will be explored in the proposed studies. Aim I. Identify interactions at the a complex that mediate ct-globin mRNA stabilization. Aim II. Define the mechanism(s) of _-globin mRNA stabilization and how a-globin mRNA evades decay in erythroid cells. Aim III. Determine how ctCPs enhance nuclear processing of ct-globin transcripts and how these nuclear events integrate with aCP-mediated cytoplasmic controls. These studies will extend our prior work on ct-globin gene expression, define novel pathways of mRNA decay, and establish a paradigm for coordinated nuclear and cytoplasmic post-transcriptional controls in erythroid gene expression.