AtMBP‐1, an alternative translation product of LOS2, affects abscisic acid responses and is modulated by the E3 ubiquitin ligase AtSAP5. (19th September 2013)

• Record Type: Journal Article
• Authors: Kang, Miyoung; Abdelmageed, Haggag; Lee, Seonghee; Reichert, Angelika; Mysore, Kirankumar S.; Allen, Randy D.
• Is Part Of: Plant journal. Volume 76:Number 3(2013:Nov.)
• Page Start: 481
• Page End: 493
• Publication Date: 2013-09-19
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12312
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12312-abs-0001"> <title>Summary</title> <p>The <italic>LOS2</italic> gene in Arabidopsis encodes an enolase with 72% amino acid sequence identity with human ENO1. In mammalian cells, the α‐enolase (<italic>ENO1</italic>) 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 <italic>c‐</italic>myc binding protein (MBP‐1), which is alternatively translated from the second start codon of <italic>ENO1</italic> 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 <italic>LOS2</italic> 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 <italic>in vivo</italic> and is stabilized by the proteasome inhibitor MG132, indicating that it is degraded via the ubiquitin‐dependent proteasome pathway. Arabidopsis plants that over‐express <italic>AtMBP</italic>‐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 <italic>in vivo</italic> and abolished the developmental defects associated with AtMBP‐1 over‐expression. Thus, AtMBP‐1 is as a bona fide alternative translation product of <italic>LOS2</italic>. Accumulation of this factor is limited by ubiquitin‐dependent destabilization, apparently mediated by AtSAP5.</p> </abstract>