TOX, a Novel Regulator of Thymocyte Selection

描述(申请人提供)：胸腺产生大量细胞，这些细胞不能完全成熟并在原位死亡。这是β选择、正选择和负选择过程的结果，这些过程对T细胞发育的不同阶段施加了严格的控制。β选择和正选择都是导致基因表达稳定变化的细胞分化事件。在这些关键的发育转变过程中，关于基因表达的分子控制仍有许多需要了解。 我们最近发现了一种新的胸腺细胞选择调节基因，我们称之为TOX(胸腺细胞选择相关HMG-box蛋白)。顾名思义，TOX是核蛋白HMG-box超家族的一员。HMG-box蛋白是结合DNA、调节多蛋白转录调节复合体形成和/或参与调节染色质可及性的结构因子。TOX也属于HMG-box蛋白的一个保守的小亚家族。TOX在胸腺中的表达受到严格的调控，并与β选择和正选择有关。数据表明，TOX在转基因小鼠胸腺中的表达足以启动这两个分化过程。这包括促进CD8T细胞的谱系承诺，而不是CD4谱系的承诺。我们建议进一步研究这种新的核蛋白的生物学功能。具体的方法包括：确定TOX及其家族成员在淋巴细胞发育过程中的表达，分析TOX的生化特性，确定蛋白的亚细胞和核内定位，确定调节其表达的信号通路，在体外和体内对各种形式的TOX进行结构/功能分析，产生TOX缺陷小鼠，识别与TOX结构域相互作用的其他蛋白质，并在正选择的背景下确定该核蛋白的基因靶标。

DESCRIPTION (provided by applicant): The thymus generates a vast excess of cells that fail to complete maturation and die in situ. This is a result of the processes of beta-selection, positive selection, and negative selection that place stringent controls on various stages of T cell development. Both beta-selection and positive selection are cell differentiation events that result in stable changes in gene expression. There is still much to learn about the molecular control of gene expression during these critical developmental transitions. We have recently identified a gene encoding a novel regulator of thymocyte selection we termed TOX (thymocyte selection associated HMG-box protein). As its name implies, TOX is a member of the HMG-box superfamily of nuclear proteins. HMG-box proteins are architectural factors that bind DNA and regulate formation of mutiprotein transcriptional regulatory complexes and/or are involved in regulating chromatin accessibility. TOX also belongs to a small conserved subfamily of HMG-box proteins. Expression of TOX in the thymus is tightly regulated and is associated with both beta-selection and positive selection. Data indicate that expression of TOX in the thymus of transgenic mice is sufficient to initiate both of these differentiation processes. This includes promotion of CD8 T cell lineage commitment at the expense of CD4 lineage commitment. We propose to further investigate the biological functions of this novel nuclear protein. Specific approaches are outlined to; determine the expression of TOX and family members during lymphocyte development, analyze biochemical characteristics of TOX, determine subcellular and intranuclear localization of the protein, identify signaling pathways that regulate its expression, perform a structure/function analysis of various forms of TOX in vitro and in vivo, produce TOX deficient mice, identify other proteins that interact with domains of TOX and identify gene targets for this nuclear protein in the context of positive selection.