title: Elements proximal to and within the transmembrane domain mediate the organelle-to-organelle movement of bZIP28 under ER stress conditions.
abstract: 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.
authors.affiliation: Plant Sciences Institute, Iowa State University, Ames, IA 50011, USA.
authors.forename: Renu
authors.initials: R
authors.lastname: Srivastava
authors.forename: Yani
authors.initials: Y
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Deng
authors.forename: Federica
authors.initials: F
authors.lastname: Brandizzi
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Howell
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D022181:COP-Coated Vesicles / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D059865:Endoplasmic Reticulum Stress; D006056:Golgi Apparatus / Q000378:metabolism*; D008969:Molecular Sequence Data; D054730:Protein Interaction Domains and Motifs; D021381:Protein Transport; D050683:R-SNARE Proteins / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D050683:R-SNARE Proteins; C099591:SAR1 protein, Arabidopsis; C530495:bZIP28 protein, Arabidopsis