MOLECULAR MECHANISMS OF CHROMOSOME CHOICE

描述(改编自研究人员摘要)：这个项目的目标是 明确决定Xist mRNA稳定性的机制。基于以前的 通过研究人员的工作，小鼠Xist基因的结构已经被 修改后包括了关于该基因3‘端的新信息。调查员 已经表明，基因的这个区域比以前要大得多 据报道。小鼠与人的已揭示序列比较 在新的3‘端有相似性。使用Northern分析和核糖核酸酶 保护实验中，研究人员已经证实了Xist和Xist两种mRNA 异构体是由一种涉及差异聚腺苷酸化的机制产生的。 这些多聚腺苷酸化位点位于新鉴定的3‘序列中。 其他表达研究表明，Xist mRNA的异构体是 发育受调节，因此表现出不同的稳定性。这 表达模式表明，调控元件可能相互作用 与每一种mRNA亚型不同，这反过来可能影响Xist 在发育的早期表达。这些数据表明，Xist的mrna亚型。 不依赖于时间的变化和习的发展规律 在此期间，异构体受到mRNA稳定性的影响 观察到所选X染色体的上调。 导致XIST稳定的具体机制仍然很差 特色化的。虽然在早期开发Xist是不稳定的，但在 开发Xist非常稳定(T1/2=&gt；5小时)。最近的数据显示 令人怀疑Xist的5‘结尾在本规则中的重要性。这个 研究人员计划探索Xist的新3‘端在基因中的作用 稳定性。他还建议推行发展调节机制 从两个方向分析了Xist的稳定性。首先，一个完整的突变分析 将完成Xist和与Xist紧邻的区域的合并。第二， 研究人员计划评估甲基化途径中的基因并定义 它们在决定Xist mRNA稳定性中的作用。

DESCRIPTION (Adapted from investigator's abstract): The goal of this project is to define the mechanism that determines Xist mRNA stability. Based on previous work by the investigator, the structure of the murine Xist gene has been revised to include new information on the 3' end of the gene. The investigator has shown that this area of the gene is significantly larger than previously reported. Sequence comparison between mouse and human revealed sequence similarity in the new 3' ends. Using both Northern analysis and RNAse protection experiments, the investigator has confirmed that both Xist mRNA isoforms are produced by a mechanism involving differential polyadenylation. These polyadenylation sites are located in the new 3' sequences identified. Additional expression studies have shown that Xist mRNA isoforms are developmentally regulated, and therefore show different stabilities. This pattern of expression suggests that regulatory elements may interact differentially with each mRNA isoform, which in turn may influences Xist expression early in development. The data suggest that Xist mRNA isoforms change independently of Tsix and that the developmental regulation of the Xist isoforms is influenced by mRNA stabilization during the period in which upregulation of the chosen X chromosome is observed. The specific mechanism responsible for Xist stability remains poorly characterized. Although early in development Xist is unstable, after development Xist is exceptionally stable (T1/2 = >5 hr). Recent data have placed in doubt the importance of the 5' end of Xist in this regulation. The investigator plans to explore the role of the new 3' end of Xist in gene stability. He also proposes to pursue the mechanism of developmental regulation of Xist stability from two directions. First, a complete a mutational analysis of Xist and the regions immediately adjacent to Xist will be done. Second, the investigator plans to evaluate genes in the methylation pathway and define their role in determining Xist mRNA stability.