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  • The EMBO Journal (2001) 20, 2742 - 2756
  • doi:10.1093/emboj/20.11.2742

SKP1–SnRK protein kinase interactions mediate proteasomal binding of a plant SCF ubiquitin ligase

Rosa Farrás1, Alejandro Ferrando1, Ján Jásik1,2, Tatjana Kleinow1, László Ökrész3, Antonio Tiburcio4, Klaus Salchert5, Carlos del Pozo6, Jeff Schell1 and Csaba Koncz1,3

  1. Max-Planck Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, D-50829 Cologne, Germany
  2. Department of Plant Physiology, Comenius University, Mlynska dolina B2, 84215 Bratislava, Slovakia
  3. Institute of Plant Biology, Biological Research Center of Hungarian Academy of Sciences, H-6701 Szeged, Temesvári krt. 62, Hungary
  4. Unitat de Fisiologia Vegetal, Universitat de Barcelona, Diagonal 643, 08028 Barcelona, Spain
  5. Risoe National Laboratory, Plant Biology and Biogeochemistry Department, DK-4000 Roskilde, Denmark
  6. Centro de Biologia Molecular 'Severo Ochoa', Cantoblanco, 28049 Madrid, Spain

Correspondence to:

Csaba Koncz, E-mail: koncz@mpiz-koeln.mpg.de

Received 25 September 2000; Accepted 12 April 2001; Revised 27 March 2001

Arabidopsis Snf1-related protein kinases (SnRKs) are implicated in pleiotropic regulation of metabolic, hormonal and stress responses through their interaction with the kinase inhibitor PRL1 WD-protein. Here we show that SKP1/ASK1, a conserved SCF (Skp1-cullin-F-box) ubiquitin ligase subunit, which suppresses the skp1-4 mitotic defect in yeast, interacts with the PRL1-binding C-terminal domains of SnRKs. The same SnRK domains recruit an SKP1/ASK1-binding proteasomal protein, alpha4/PAD1, which enhances the formation of a trimeric SnRK complex with SKP1/ASK1 in vitro. By contrast, PRL1 reduces the interaction of SKP1/ASK1 with SnRKs. SKP1/ASK1 is co-immunoprecipitated with a cullin SCF subunit (AtCUL1) and an SnRK kinase, but not with PRL1 from Arabidopsis cell extracts. SKP1/ASK1, cullin and proteasomal alpha-subunits show nuclear co-localization in differentiated Arabidopsis cells, and are observed in association with mitotic spindles and phragmoplasts during cell division. Detection of SnRK in purified 26S proteasomes and co-purification of epitope- tagged SKP1/ASK1 with SnRK, cullin and proteasomal alpha-subunits indicate that the observed protein interactions between SnRK, SKP1/ASK1 and alpha4/PAD1 are involved in proteasomal binding of an SCF ubiquitin ligase in Arabidopsis.

  • Keywords:

    • Arabidopsis Pleiotropic Regulatory Locus 1 (PRL1),
    • proteasome,
    • SCF ubiquitin ligase,
    • SKP1,
    • ASK1,
    • Snf1-related protein kinase