TOX, a Novel Regulator of Thymocyte Selection

描述（由申请方提供）：胸腺产生大量过量的细胞，这些细胞无法完全成熟并原位死亡。这是β选择、阳性选择和阴性选择过程的结果，这些过程对T细胞发育的各个阶段进行了严格控制。β选择和阳性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还有很多需要了解的。 我们最近已经确定了一个基因编码一种新的调节胸腺细胞的选择，我们称之为TOX（胸腺细胞选择相关HMG盒蛋白）。顾名思义，TOX是核蛋白HMG盒超家族的成员。HMG盒蛋白是一种结构因子，它与DNA结合，调节多蛋白转录调控复合物的形成和/或参与调节染色质可及性。TOX也属于HMG盒蛋白的小保守亚家族。胸腺中TOX的表达受到严格调控，并与β选择和阳性选择相关。数据表明，转基因小鼠胸腺中TOX的表达足以启动这两种分化过程。这包括以CD 4谱系定型为代价促进CD 8 T细胞谱系定型。我们建议进一步研究这种新的核蛋白的生物学功能。概述了具体的办法;确定淋巴细胞发育过程中TOX及其家族成员的表达，分析TOX的生物化学特征，确定蛋白质的亚细胞和核内定位，鉴定调节其表达的信号传导途径，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，鉴定与TOX结构域相互作用的其他蛋白质，并在正选择的背景下鉴定该核蛋白的基因靶。

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.