title: Cullins 3a and 3b assemble with members of the broad complex/tramtrack/bric-a-brac (BTB) protein family to form essential ubiquitin-protein ligases (E3s) in Arabidopsis.
abstract: Selective modification of proteins by ubiquitination is directed by diverse families of ubiquitin-protein ligases (or E3s). A large collection of E3s use Cullins (CULs) as scaffolds to form multisubunit E3 complexes in which the CUL binds a target recognition subcomplex and the RBX1 docking protein, which delivers the activated ubiquitin moiety. Arabidopsis and rice contain a large collection of CUL isoforms, indicating that multiple CUL-based E3s exist in plants. Here we show that Arabidopsis CUL3a and CUL3b associate with RBX1 and members of the broad complex/tramtrack/bric-a-brac (BTB) protein family to form BTB E3s. Eighty genes encoding BTB domain-containing proteins were identified in the Arabidopsis genome, indicating that a diverse array of BTB E3s is possible. In addition to the BTB domain, the encoded proteins also contain various other interaction motifs that likely serve as target recognition elements. DNA microarray analyses show that BTB genes are expressed widely in the plant and that tissue-specific and isoform-specific patterns exist. Arabidopsis defective in both CUL3a and CUL3b are embryo-lethal, indicating that BTB E3s are essential for plant development.
authors.affiliation: Department of Genetics, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Gingerich
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Gagne
authors.forename: Donald W
authors.initials: DW
authors.lastname: Salter
authors.forename: Hanjo
authors.initials: H
authors.lastname: Hellmann
authors.forename: Mark
authors.initials: M
authors.lastname: Estelle
authors.forename: Ligeng
authors.initials: L
authors.lastname: Ma
authors.forename: Richard D
authors.initials: RD
authors.lastname: Vierstra
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins; D002352:Carrier Proteins / Q000737:chemistry*; D003062:Codon; D044842:Cullin Proteins; D004247:DNA / Q000737:chemistry; D018506:Gene Expression Regulation, Plant; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008954:Models, Biological; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D010802:Phylogeny; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D025801:Ubiquitin / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry*
chemical_list: C500789:AT1G26830 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D003062:Codon; D044842:Cullin Proteins; D020033:Protein Isoforms; D025801:Ubiquitin; C500790:cullin 3B protein, Arabidopsis; D004247:DNA; D044767:Ubiquitin-Protein Ligases