title: AtMBP-1, an alternative translation product of LOS2, affects abscisic acid responses and is modulated by the E3 ubiquitin ligase AtSAP5.
abstract: The LOS2 gene in Arabidopsis encodes an enolase with 72% amino acid sequence identity with human ENO1. In mammalian cells, the α-enolase (ENO1) gene encodes both a 48 kDa glycolytic enzyme and a 37 kDa transcriptional suppressor protein that are targeted to different cellular compartments. The tumor suppressor c-myc binding protein (MBP-1), which is alternatively translated from the second start codon of ENO1 transcripts, is preferentially localized in nuclei while α-enolase is found in the cytoplasm. We report here that an Arabidopsis MBP-1-like protein (AtMBP-1) is alternatively translated from full-length LOS2 transcripts using a second start codon. Like mammalian MBP-1, this truncated form of LOS2 has little, if any, enolase activity, indicating that an intact N-terminal region of LOS2 is critical for catalysis. AtMBP-1 has a short half-life in vivo and is stabilized by the proteasome inhibitor MG132, indicating that it is degraded via the ubiquitin-dependent proteasome pathway. Arabidopsis plants that over-express AtMBP-1 are hypersensitive to abscisic acid (ABA) during seed germination and show defects in vegetative growth and lateral stem development. AtMBP-1 interacts directly with the E3 ubiquitin ligase AtSAP5 and co-expression of these proteins resulted in destabilization of AtMBP-1 in vivo and abolished the developmental defects associated with AtMBP-1 over-expression. Thus, AtMBP-1 is as a bona fide alternative translation product of LOS2. Accumulation of this factor is limited by ubiquitin-dependent destabilization, apparently mediated by AtSAP5.
authors: Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK, 74078, USA; Institute for Agricultural Bioscience, Oklahoma State University, Ardmore, OK, 79413, USA.
authors: Miyoung
authors: M
authors: Kang
authors: Haggag
authors: H
authors: Abdelmageed
authors: Seonghee
authors: S
authors: Lee
authors: Angelika
authors: A
authors: Reichert
authors: Kirankumar S
authors: KS
authors: Mysore
authors: Randy D
authors: RD
authors: Allen
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017398:Alternative Splicing; D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D010751:Phosphopyruvate Hydratase / Q000502:physiology*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D012333:RNA, Messenger; D025801:Ubiquitin; D000040:Abscisic Acid; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C000588609:LOS2 protein, Arabidopsis; D010751:Phosphopyruvate Hydratase; C557394:SAP5 protein, Arabidopsis
keywords: Alternative translation; AtMBP-1; LOS2; abscisic acid signaling; post-translational regulation; ubiquitin ligase