J Integr Plant Biol. ›› 2013, Vol. 55 ›› Issue (1): 108-120.DOI: 10.1111/jipb.12014

• Research Articles • Previous Articles    

Arabidopsis RING Peroxins are E3 Ubiquitin Ligases that Interact with Two Homologous Ubiquitin Receptor Proteins

Navneet Kaur1, Qingzhen Zhao2, Qi Xie2 and Jianping Hu1*   

  1. 1MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
    2Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
  • Received:2012-10-19 Accepted:2012-11-20 Published:2013-01-01
  • About author:*Corresponding author Tel: +1 517 432 4620; Fax: +1 517 353 9168; E-mail: huji@msu.edu


Peroxisomes are essential eukaryotic organelles that mediate various metabolic processes. Peroxisome import depends on a group of peroxisome biogenesis factors called peroxins, many of which are evolutionarily conserved. PEX2, PEX10, and PEX12 are three RING-finger-domain-containing integral membrane peroxins crucial for protein import. In yeast (Saccharomyces cerevisae), RING peroxins act as E3 ligases, facilitating the recycling of the peroxisome import receptor protein PEX5 through ubiquitination. In plants, RING peroxins are essential to plant vitality. To elucidate the mode of action of the plant RING peroxins, we employed in vitro assays to show that the Arabidopsis RING peroxins also have E3 ligase activities. We also identified a PEX2-interacting protein, DSK2b, which is a member of the ubiquitin receptor family known to function as shuttle factors ferrying polyubiquitinated substrates to the proteasome for degradation. DSK2b and its tandem duplicate DSK2a are localized in the cytosol and the nucleus, and both interact with the RING domain of PEX2 and PEX12. DSK2 artificial microRNA lines did not display obvious defects in plant growth or peroxisomal processes, indicating functional redundancies among Arabidopsis ubiquitin receptor proteins. Our results suggest that Arabidopsis RING peroxins can function as E3 ligases and act together with the ubiquitin receptor protein DSK2 in the peroxisomal membrane-associated protein degradation system.

Key words: Arabidopsis, RING domain proteins, peroxisomes, ubiquitin receptor

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