Tanaka-Matakatsu Miho, Miller John, Du Wei
Ben May Department for Cancer Research, The University of Chicago, Chicago, IL, 60637, USA.
Protein Cell. 2015 Jan;6(1):68-78. doi: 10.1007/s13238-014-0101-9. Epub 2014 Sep 20.
Pax6 and its Drosophila homolog Eyeless (Ey) play essential roles during eye development. Ey/Pax6 contains two distinct DNA binding domains, a Paired domain (PD) and a Homeodomain (HD). While Ey/Pax6 PD is required for the expression of key regulators of retinal development, relatively little is known about the HD-dependent Ey function. In this study, we used the UAS/GAL4 system to determine the functions of different Ey domains on cell growth and on retinal development. We showed that Ey can promote cell growth, which requires the HD but not the PD. In contrast, the ability of Ey to activate Ato expression and induce ectopic eye formation requires the PD but not the HD. Interestingly, deletion of the HD enhanced Ey-dependent ectopic eye induction while overexpression of the HD only Ey forms antagonizes ectopic eye induction. These studies revealed a novel function of Ey HD on cell growth and a novel antagonistic effect of Ey HD on Ey PD-dependent eye induction. We further show the third helix of the Ey HD can directly interact with the RED subdomain in Ey PD and that deletion of the HD increased the binding of Ey PD to its target. These results suggest that the direct interaction between the HD and the PD potentially mediates their antagonistic effects. Since different Ey splicing forms are expressed in overlapping regions during normal development, we speculate that the expression ratios of the different Ey splice forms potentially contribute to the regulation of growth and differentiation of these tissues.
Pax6及其果蝇同源物眼无（Ey）在眼睛发育过程中发挥着重要作用。Ey/Pax6包含两个不同的DNA结合结构域，一个配对结构域（PD）和一个同源结构域（HD）。虽然Ey/Pax6 PD是视网膜发育关键调节因子表达所必需的，但对于HD依赖的Ey功能了解相对较少。在本研究中，我们使用UAS/GAL4系统来确定不同Ey结构域对细胞生长和视网膜发育的功能。我们发现Ey可以促进细胞生长，这需要HD而不是PD。相反，Ey激活Ato表达和诱导异位眼形成的能力需要PD而不是HD。有趣的是，HD的缺失增强了Ey依赖的异位眼诱导，而仅HD形式的Ey过表达则拮抗异位眼诱导。这些研究揭示了Ey HD对细胞生长具有新功能，以及Ey HD对Ey PD依赖的眼诱导具有新的拮抗作用。我们进一步表明，Ey HD的第三个螺旋可以直接与Ey PD中的RED亚结构域相互作用，并且HD的缺失增加了Ey PD与其靶标的结合。这些结果表明，HD和PD之间的直接相互作用可能介导了它们的拮抗作用。由于不同的Ey剪接形式在正常发育过程中在重叠区域表达，我们推测不同Ey剪接形式的表达比例可能有助于调节这些组织的生长和分化。
