Werner Kathrin, Donow Cornelia, Pandur Petra
Institut für Biochemie und Molekulare Biologie, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
Genesis. 2017 Apr;55(4). doi: 10.1002/dvg.23030. Epub 2017 Apr 3.
The LIM-homeodomain transcription factor Tailup (Tup) is a component of the complex cardiac transcriptional network governing specification and differentiation of cardiac cells in Drosophila. LIM-domain containing factors are known to interact with the adaptor molecule Chip/Ldb1 to form higher order protein complexes to regulate gene expression thereby determining a cell's developmental fate. However, with respect to Drosophila heart development, it has not been investigated yet, whether Chip and tup interact to regulate the generation of different cardiac cell types. Here we show that Chip is required for normal heart development and that it interacts with tup in this context. Particularly the number of Odd skipped-expressing pericardial cells depends on balanced amounts of Chip and Tup. Data from luciferase assays using Hand- and even-skipped reporter constructs in Drosophila S2 cells indicate that Chip and Tup act as a tetrameric complex on the regulatory regions of Hand and even-skipped (eve). Finally we have identified and verified five Tup binding sites in the eve mesodermal enhancer, which adds Tup as novel factor to directly regulate eve expression. Taken together this study provides novel findings regarding cardiac gene expression regulation in Drosophila.
LIM 同源结构域转录因子 Tailup（Tup）是果蝇心脏细胞特化和分化过程中复杂心脏转录网络的一个组成部分。已知含 LIM 结构域的因子与衔接分子 Chip/Ldb1 相互作用，形成高阶蛋白复合物来调节基因表达，从而决定细胞的发育命运。然而，关于果蝇心脏发育，Chip 和 tup 是否相互作用以调节不同心脏细胞类型的产生尚未得到研究。在这里，我们表明 Chip 是正常心脏发育所必需的，并且在这种情况下它与 tup 相互作用。特别是表达 Odd skipped 的心包细胞数量取决于 Chip 和 Tup 的平衡量。在果蝇 S2 细胞中使用 Hand 和 even-skipped 报告基因构建体进行的荧光素酶测定数据表明，Chip 和 Tup 在 Hand 和 even-skipped（eve）的调控区域上作为四聚体复合物起作用。最后，我们在 eve 中胚层增强子中鉴定并验证了五个 Tup 结合位点，这将 Tup 作为直接调节 eve 表达的新因子。综上所述，这项研究提供了关于果蝇心脏基因表达调控的新发现。
