title: The E3 ligase AtCHIP positively regulates Clp proteolytic subunit homeostasis.
abstract: The caseinolytic peptidase (Clp) core proteins are essential for plant growth and development, especially for chloroplast function. Antisense or overexpression of ClpP4, which is one of the Clp core subunits, causes chlorotic phenotypes in Arabidopsis. An E3 ligase gene, AtCHIP, has previously been found to ubiquitylate ClpP4 in vitro. ClpP4 antisense and overexpressing plants that also overexpressed AtCHIP were constructed to explore the effect of AtCHIP on ClpP4. Overexpression of AtCHIP was found to rescue the chlorotic phenotypes of both ClpP4 antisense and overexpressing plants. The unbalanced levels of Clp core proteins in ClpP4 antisense and overexpressing plants with overexpression of AtCHIP were similar to wild-type levels, suggesting that AtCHIP regulates Clp core proteins. The results also show that AtCHIP can interact with ClpP3 and ClpP5 in yeast and ubiquitylate ClpP3 and ClpP5 in vitro. This suggests that AtCHIP is directly related to ClpP3 and ClpP5. Given these results, the inference is that through selective degradation of Clp subunits, AtCHIP could positively regulate homeostasis of Clp proteolytic subunits and maximize the production of functional chloroplasts. Similar results were obtained from transgenic tobacco plants, suggesting that regulation of the Clp protease by AtCHIP is conserved.
authors.affiliation: Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, Zhejiang Province, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Wei
authors.affiliation: Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, Zhejiang Province, China.
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Qiu
authors.affiliation: Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, Zhejiang Province, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.affiliation: Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, Zhejiang Province, China.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Hu
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA.
authors.forename: Rongbin
authors.initials: R
authors.lastname: Hu
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA.
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Sun
authors.affiliation: Robert W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, New York 14853, USA and Department of Plant Breeding and Genetics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, Zhejiang Province, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Lv
authors.affiliation: Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, Zhejiang Province, China guoxin.shen@ttu.edu.
authors.forename: Guoxin
authors.initials: G
authors.lastname: Shen
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D049071:Endopeptidase Clp / Q000235:genetics* / Q000378:metabolism; D006706:Homeostasis; D059748:Proteolysis; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D025801:Ubiquitin; C511865:CHIP protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; D049071:Endopeptidase Clp
keywords: AtCHIP; Clp proteolytic subunits; ClpP3; ClpP4; ClpP5; chloroplast protease; protein homeostasis.