Plant Sciences Institute, Iowa State University, Ames, IA 50011, USA.
Plant J. 2012 Jun;70(6):1033-42. doi: 10.1111/j.1365-313X.2012.04943.x. Epub 2012 Mar 31.
Arabidopsis bZIP28, an ER membrane-associated transcription factor, is activated in response to conditions that induce ER stress-adverse environmental conditions or exposure to ER stress agents such as tunicamycin and dithiothreitol. Upon stress treatment, bZIP28 exits the ER and moves to the Golgi, where it is proteolytically processed, releasing its transcriptional component, which relocates to the nucleus. In this study, we tracked the movement of GFP-tagged bZIP28 in an effort to understand its mobilization from the ER and release from the Golgi. We identified a small region in bZIP28 that is rich in dibasic amino acids and proximal to the transmembrane domain required for its movement from the ER. In response to ER stress, bZIP28 showed enhanced interaction with Sar1 and Sec12, components of the COPII machinery. We demonstrated that the dibasic amino acid-rich region in bZIP28 is involved in the interaction with Sar1. Upon migration to the Golgi, bZIP28 is proteolytically processed by proteases S1P and S2P. We found a putative helix-breaking residue in the transmembrane domain of bZIP28 to be crucial for its processing and liberation from Golgi bodies. Thus, in response to stress, bZIP28 moves from organelle to organelle by interaction of critical elements in the molecule with the transport and/or proteolytic machinery resident in the various organelles.
拟南芥 bZIP28 是内质网膜相关转录因子，可响应内质网应激诱导的不利环境条件或内质网应激剂（如衣霉素和二硫苏糖醇）的暴露而被激活。在应激处理后，bZIP28 离开内质网并转移到高尔基体，在那里它被蛋白水解加工，释放其转录组件，该组件重新定位到细胞核。在这项研究中，我们跟踪 GFP 标记的 bZIP28 的运动，以了解其从内质网的动员和从高尔基体的释放。我们确定了 bZIP28 中富含二碱基氨基酸的小区域，该区域靠近其从内质网运动所需的跨膜结构域。在应对内质网应激时，bZIP28 与 Sar1 和 Sec12 （COPII 机制的组成部分）的相互作用增强。我们证明 bZIP28 中富含二碱基氨基酸的区域参与与 Sar1 的相互作用。迁移到高尔基体后，bZIP28 被蛋白酶 S1P 和 S2P 进行蛋白水解加工。我们发现 bZIP28 的跨膜结构域中的一个假定螺旋断裂残基对于其加工和从高尔基体体的释放至关重要。因此，在应激响应下，bZIP28 通过分子中的关键元素与驻留在各个细胞器中的运输和/或蛋白水解机制相互作用，从细胞器到细胞器移动。
