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Abstract Detail


Organelle Biology

kaur, Navneet [1], Fan, Jilian [1], Quan, Sheng [1], Hu, Jianping [1].

The Role of Two Ubiquitin-Like Proteins in Arabidopsis Peroxisome Biogenesis and Function.

Plant peroxisomes are dynamic organelles that play a vital role in plant growth and development. Peroxins are an eclectic set of proteins necessary for peroxisome biogenesis and import of matrix proteins from the cytosol. PEX2 is a RING family Peroxin which has been shown to be essential for viability and to be involved in the photomorphogenic response. Yeast two hybrid approach was employed to identify PEX2 interacting factors and resulted in the retrieval of an Ubiquitin-Like protein, named AtPXI1 (PEX2 Interactor protein). Arabidopsis was found to have a highly conserved paralog of this gene, AtPXI2. AtPXI genes are present in tandem and oriented in head to tail fashion on the chromosome. The AtPXI proteins constitute an N-terminal Ubiquitin-Like (UBL) domain, a C-terminal Ubiquitin Associated domain (UBA) and four chaperonin binding sites in the medial region. Both AtPXIs interact with the RING domain of PEX2. Deletion constructs are being made to delineate the AtPXI domain specific to this interaction. Using fluorescence microscopy we demonstrated that GFP-fusions of AtPXI1 and AtPXI2 localize to the peroxisome. T-DNA insertion lines of AtPXIs were identified and are being investigated to determine the functional role of the AtPXIs. RNAi lines are concurrently being analyzed to further elucidate the functions of the AtPXIs in Arabidopsis. UBL-UBA proteins are believed to function as shuttle factors, relaying ubiquitinated proteins to the proteasome. Drawing analogy from the ERAD (Endoplasmic Reticulum Associated Degradation) model, the presence of RING proteins (putative E3 ligases), E2, AAA-ATPases and UBL-UBA proteins in the peroxisomes prompts us to speculate that peroxisomes also have a ubiquitin-proteasome type of proteolytic system associated with them, which regulates peroxisome biogenesis and function by targeting selective peroxisome proteins for degradation.


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1 - Michigan State University, MSU-DOE Plant Research Laboratory, East Lansing, MI, 48824, USA

Keywords:
peroxisomes
UBL/UBA proteins
PEX2.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P18029
Abstract ID:1894


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