Department of Cell and Developmental Biology and the Penn Cardiovascular Institute, Philadelphia, PA 19104, USA.
Exp Biol Med (Maywood). 2010 May;235(5):569-76. doi: 10.1258/ebm.2010.009318.
TBX1 encodes a DNA binding transcription factor that is commonly deleted in human DiGeorge syndrome and plays an important role in heart development. Mechanisms of Tbx1 function, such as Tbx1 interacting regulatory proteins and transcriptional target specificity, are largely unknown. Ash2l is the mammalian homolog of Drosophila Ash2 (absent small homeotic 2) and is a core component of a multimeric histone methyltransferase complex that epigenetically regulates transcription via methylation of histone lysine residues. We undertook an unbiased yeast two-hybrid screen to look for functionally relevant Tbx1-interacting proteins and report a physical and functional interaction between Tbx1 and Ash2l. Tbx1 interacts with Ash2l in both yeast and mammalian cells and Ash2l acts as a transcriptional co-activator in luciferase reporter assays. Expression analysis shows that Tbx1 and Ash2l have overlapping mRNA and protein expression patterns during development. By generating an Ash2l knockout mouse utilizing gene-trap technology, we show that although Ash2l heterozygous mice are normal, Ash2l-null embryos die early during gestation. Thus, Ash2l is required for the earliest stages of embryogenesis. Furthermore, our finding of a physical interaction between Tbx1 and Ash2l suggest that at least some functions of Tbx1 may be mediated by direct interactions with a histone methyltransferase complex.
TBX1 编码一种 DNA 结合转录因子，该因子在人类 DiGeorge 综合征中通常缺失，并在心脏发育中发挥重要作用。Tbx1 功能的机制，例如 Tbx1 相互作用的调节蛋白和转录靶标特异性，在很大程度上是未知的。Ash2l 是果蝇 Ash2（absent small homeotic 2）的哺乳动物同源物，是多聚体组蛋白甲基转移酶复合物的核心组成部分，通过组蛋白赖氨酸残基的甲基化来表观遗传调控转录。我们进行了一项无偏酵母双杂交筛选，以寻找具有功能相关性的 Tbx1 相互作用蛋白，并报告了 Tbx1 和 Ash2l 之间的物理和功能相互作用。Tbx1 在酵母和哺乳动物细胞中均与 Ash2l 相互作用，并且 Ash2l 在荧光素酶报告基因测定中作为转录共激活因子起作用。表达分析表明，Tbx1 和 Ash2l 在发育过程中具有重叠的 mRNA 和蛋白表达模式。通过利用基因捕获技术生成 Ash2l 敲除小鼠，我们表明尽管 Ash2l 杂合子小鼠正常，但 Ash2l 缺失胚胎在妊娠早期很早就死亡。因此，Ash2l 是胚胎发生的最早阶段所必需的。此外，我们发现 Tbx1 和 Ash2l 之间存在物理相互作用，这表明 Tbx1 的至少某些功能可能通过与组蛋白甲基转移酶复合物的直接相互作用来介导。
