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标题：E3 ubiquitin ligase SP1 regulates peroxisome biogenesis in Arabidopsis
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作者：Ronghui Pan ; John Satkovich ; Jianping Hu 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：46
页码：E7307-E7316
DOI：10.1073/pnas.1613530113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificancePeroxisomes are eukaryotic organelles crucial for development. Peroxisomal matrix proteins are imported by the peroxisome import machinery composed of peroxins (PEX proteins), but how the function of these PEX proteins is regulated is largely unknown. We discovered in Arabidopsis that the ubiquitin-proteasome system regulates peroxisome protein import via an E3 ubiquitin ligase, SP1 (suppressor of ppi1 locus1), which targets PEX13 and possibly several other components of the peroxisome matrix protein import machinery for degradation. Our data demonstrate that the same E3 ubiquitin ligase can be shared by metabolically linked peroxisomes and chloroplasts to promote the destabilization of distinct components of the two import machineries, suggesting that the ubiquitin-proteasome system may represent an important regulatory mechanism coordinating the biogenesis of functionally associated organelles. Peroxisomes are ubiquitous eukaryotic organelles that play pivotal roles in a suite of metabolic processes and often act coordinately with other organelles, such as chloroplasts and mitochondria. Peroxisomes import proteins to the peroxisome matrix by peroxins (PEX proteins), but how the function of the PEX proteins is regulated is poorly understood. In this study, we identified the Arabidopsis RING (really interesting new gene) type E3 ubiquitin ligase SP1 [suppressor of plastid protein import locus 1 (ppi1) 1] as a peroxisome membrane protein with a regulatory role in peroxisome protein import. SP1 interacts physically with the two components of the peroxisome protein docking complex PEX13-PEX14 and the (RING)-finger peroxin PEX2. Loss of SP1 function suppresses defects of the pex14-2 and pex13-1 mutants, and SP1 is involved in the degradation of PEX13 and possibly PEX14 and all three RING peroxins. An in vivo ubiquitination assay showed that SP1 has the ability to promote PEX13 ubiquitination. Our study has revealed that, in addition to its previously reported function in chloroplast biogenesis, SP1 plays a role in peroxisome biogenesis. The same E3 ubiquitin ligase promotes the destabilization of components of two distinct protein-import machineries, indicating that degradation of organelle biogenesis factors by the ubiquitin-proteasome system may constitute an important regulatory mechanism in coordinating the biogenesis of metabolically linked organelles in eukaryotes.
关键词：peroxisome biogenesis ; E3 ubiquitin ligase ; protein import ; peroxin ; SP1