PMID:19435936

Citation	Koroleva, OA, Calder, G, Pendle, AF, Kim, SH, Lewandowska, D, Simpson, CG, Jones, IM, Brown, JW and Shaw, PJ (2009) Dynamic behavior of Arabidopsis eIF4A-III, putative core protein of exon junction complex: fast relocation to nucleolus and splicing speckles under hypoxia. Plant Cell 21:1592-606
Abstract	Here, we identify the Arabidopsis thaliana ortholog of the mammalian DEAD box helicase, eIF4A-III, the putative anchor protein of exon junction complex (EJC) on mRNA. Arabidopsis eIF4A-III interacts with an ortholog of the core EJC component, ALY/Ref, and colocalizes with other EJC components, such as Mago, Y14, and RNPS1, suggesting a similar function in EJC assembly to animal eIF4A-III. A green fluorescent protein (GFP)-eIF4A-III fusion protein showed localization to several subnuclear domains: to the nucleoplasm during normal growth and to the nucleolus and splicing speckles in response to hypoxia. Treatment with the respiratory inhibitor sodium azide produced an identical response to the hypoxia stress. Treatment with the proteasome inhibitor MG132 led to accumulation of GFP-eIF4A-III mainly in the nucleolus, suggesting that transition of eIF4A-III between subnuclear domains and/or accumulation in nuclear speckles is controlled by proteolysis-labile factors. As revealed by fluorescence recovery after photobleaching analysis, the nucleoplasmic fraction was highly mobile, while the speckles were the least mobile fractions, and the nucleolar fraction had an intermediate mobility. Sequestration of eIF4A-III into nuclear pools with different mobility is likely to reflect the transcriptional and mRNA processing state of the cell.
Links	PubMed PMC2700535 Online version:10.1105/tpc.108.060434
Keywords	Amino Acid Sequence; Arabidopsis/drug effects; Arabidopsis/metabolism; Arabidopsis/ultrastructure; Arabidopsis Proteins/chemistry; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Cell Hypoxia; Cell Nucleolus/metabolism; Conserved Sequence; Enzyme Inhibitors/pharmacology; Eukaryotic Initiation Factor-4A/chemistry; Eukaryotic Initiation Factor-4A/genetics; Eukaryotic Initiation Factor-4A/metabolism; Green Fluorescent Proteins/analysis; Leupeptins/pharmacology; Molecular Sequence Data; Protein Transport/drug effects; Recombinant Fusion Proteins/analysis; Sequence Alignment; Sodium Azide/pharmacology; Two-Hybrid System Techniques
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ARATH:RH2	involved_in	GO:0001666: response to hypoxia	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete
ARATH:RH2	located_in	GO:0005654: nucleoplasm	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
ARATH:RH2	located_in	GO:0005730: nucleolus	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
ARATH:RH2	located_in	GO:0016607: nuclear speck	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
ARATH:RH2	part_of	GO:0035145: exon-exon junction complex	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete

References

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