State Key Laboratory of Reproductive Biology and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Datun Road, Chaoyang, Beijing 100101, P.R. China.
Development. 2009 Dec;136(24):4133-42. doi: 10.1242/dev.039032. Epub 2009 Nov 11.
Increasing evidence supports the idea that the regulation of stem cells requires both extrinsic and intrinsic mechanisms. However, much less is known about how intrinsic signals regulate the fate of stem cells. Studies on germline stem cells (GSCs) in the Drosophila ovary have provided novel insights into the regulatory mechanisms of stem cell maintenance. In this study, we demonstrate that a ubiquitin-dependent pathway mediated by the Drosophila eff gene, which encodes the E2 ubiquitin-conjugating enzyme Effete (Eff), plays an essential role in GSC maintenance. We show that Eff both physically and genetically interacts with dAPC2, a key component of the anaphase-promoting complex (APC), which acts as a multisubunit E3 ligase and plays an essential role in targeting mitotic regulators for degradation during exit from mitosis. This interaction indicates that Eff regulates the APC/C-mediated proteolysis pathway in GSCs. Moreover, we show that expression of a stable form of Cyclin A, but not full-length Cyclin A, results in GSC loss. Finally we show that, in common with APC2, Eff is required for the ubiquitylation of Cyclin A, and overexpression of full-length Cyclin A accelerates the loss of GSCs in the eff mutant background. Collectively, our data support the idea that Effete/APC-mediated degradation of Cyclin A is essential for the maintenance of germline stem cells in Drosophila. Given that the regulation of mitotic Cyclins is evolutionarily conserved between flies and mammals, our study also implies that a similar mechanism may be conserved in mammals.
越来越多的证据支持这样一种观点，即干细胞的调控既需要外在机制，也需要内在机制。然而，内在信号如何调节干细胞的命运知之甚少。对果蝇卵巢生殖干细胞（GSCs）的研究为干细胞维持的调控机制提供了新的见解。在这项研究中，我们证明了由果蝇 eff 基因编码的 E2 泛素连接酶 Effete（Eff）介导的泛素依赖性途径在 GSC 维持中起着至关重要的作用。我们表明 Eff 与 dAPC2 发生物理和遗传相互作用，dAPC2 是后期促进复合物（APC）的关键组成部分，作为一个多亚基 E3 连接酶，在有丝分裂退出期间对 mitotic 调节剂进行降解，从而发挥重要作用。这种相互作用表明 Eff 调节 GSCs 中的 APC/C 介导的蛋白水解途径。此外，我们表明稳定形式的 Cyclin A 的表达，但不是全长 Cyclin A 的表达，导致 GSC 丢失。最后，我们表明与 APC2 一样，Eff 是 Cyclin A 泛素化所必需的，全长 Cyclin A 的过表达加速了 eff 突变体背景下 GSCs 的丢失。总的来说，我们的数据支持这样一种观点，即 Effete/APC 介导的 Cyclin A 降解对于果蝇生殖干细胞的维持是必不可少的。鉴于有丝分裂周期蛋白的调控在果蝇和哺乳动物之间是进化保守的，我们的研究也表明，类似的机制可能在哺乳动物中保守。
