Activation and Inactivation of Immunoglubulin VH Genes

描述(申请人提供)：免疫球蛋白重链的组装 B细胞分化过程中的(IgH)基因需要两次重组事件。 首先，几个DH基因片段中的一个重排到JH基因片段以产生 DJH加入。第二，数百个VH基因片段中的一个重排成DJH 连接以产生V(D)J重组等位基因。一小部分V(D)J 重组等位基因将编码免疫球蛋白。那些制造免疫球蛋白的细胞 将终止免疫球蛋白基因的重组，这一过程称为等位基因 排除。早期的研究表明，等位基因排斥在这一步起作用 VH到DJH的重组。阻止VH重组的机制 是未知的。 在最近对IgH基因座染色质结构的研究中，我们发现VH 基因由三种不同的机制激活。最大的VH J558基因 位于该基因5‘端的家族被IL-7激活。3‘-Most 以VH8 1X和VHSM7为代表的VHS仅在包含 DJH重组等位基因。位于VHJ558和VHSM7之间的基因，由 VH10，在V-ABL转化的细胞中被激活，表明它们可能是 被酪氨酸激酶激活。 在本申请中，我们建议严格建立激活 中间基因和3β-VH基因(目标1)。然后，我们提议测试该模型 这种等位基因排斥是终止激活VH的信号的结果 基因(目标2)。这将通过体外培养和联合使用 转基因小鼠品系的体内分析。 这些研究不仅对全面理解IGH具有重要意义 基因组装，但也是为了深入了解更普遍的问题，即如何 基因组的大片段被激活。

DESCRIPTION (provided by the applicant): Assembly of immunoglobulin heavy chain (IgH) genes during B cell differentiation requires two recombination events. First, one of several DH gene segments rearrange to JH gene segments to produce DJH joins. Second, one of several hundred VH gene segments rearrange to the DJH join to produce V(D)J recombined alleles. A small proportion of V(D)J recombined alleles will encode IgH protein. Those cells that make IgH protein will terminate recombination of the IgH gene, a process referred to as allelic exclusion. Earlier studies indicate that allelic exclusion operates at the step of VH to DJH recombination. The mechanism by which VH recombination is stopped is not known. In recent studies of the chromatin structure of the IgH locus we found that VH genes are activated by three distinct mechanisms. The largest VH J558 gene family, that is at the 5' end of the locus, is activated by IL-7. The 3' -most VHS, represented by VH8 1X and VHSM7, are activated only in cells that contain DJH recombined alleles. Genes that lie between VHJ558 and VHSM7, represented by VH10, are activated in V-abl transformed cells suggesting that they may be activated by tyrosine kinases. In this application we propose to rigorously establish mechanisms that activate the intermediate and 3?-VH genes (Aim 1). We then propose to test the model that allelic exclusion is a consequence of terminating signals that activate VH genes (Aim 2). This will be accomplished by a combination of in-vitro and in-vivo analyses in genetically altered mouse strains. These studies are important not only for a comprehensive understanding of IgH gene assembly, but also for insights into the more general question of how large segments of the genome are activated.