title: Identification of the Raptor-binding motif on Arabidopsis S6 kinase and its use as a TOR signaling suppressor.
abstract: TOR (target of rapamycin) kinase signaling plays central role as a regulator of growth and proliferation in all eukaryotic cells and its key signaling components and effectors are also conserved in plants. Unlike the mammalian and yeast counterparts, however, we found through yeast two-hybrid analysis that multiple regions of the Arabidopsis Raptor (regulatory associated protein of TOR) are required for binding to its substrate. We also identified that a 44-amino acid region at the N-terminal end of Arabidopsis ribosomal S6 kinase 1 (AtS6K1) specifically interacted with AtRaptor1, indicating that this region may contain a functional equivalent of the TOS (TOR-Signaling) motif present in the mammalian TOR substrates. Transient over-expression of this 44-amino acid fragment in Arabidopsis protoplasts resulted in significant decrease in rDNA transcription, demonstrating a feasibility of developing a new plant-specific TOR signaling inhibitor based upon perturbation of the Raptor-substrate interaction.
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul 041310, South Korea.
authors.forename: Ora
authors.initials: O
authors.lastname: Son
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul 041310, South Korea.
authors.forename: Sunghan
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul 041310, South Korea.
authors.forename: Yoon-Sun
authors.initials: YS
authors.lastname: Hur
authors.affiliation: Department of Biological Science, Sookmyung Women's University, Seoul 041310, South Korea. Electronic address: ccheon@sookmyung.ac.kr.
authors.forename: Choong-Ill
authors.initials: CI
authors.lastname: Cheon
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D030821:Plants, Genetically Modified; D054730:Protein Interaction Domains and Motifs; D019893:Ribosomal Protein S6 Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; C496442:Raptor1 protein, Arabidopsis; D019869:Phosphatidylinositol 3-Kinases; C512171:TOR protein, Arabidopsis; D019893:Ribosomal Protein S6 Kinases
keywords: Arabidopsis ribosomal S6 kinase; AtRaptor; TOR; rDNA transcription