title: Identification of Arabidopsis SUMO-interacting proteins that regulate chromatin activity and developmental transitions.
abstract: Posttranslational modification of proteins by small ubiquitin-like modifier (SUMO) plays essential roles in eukaryotic growth and development. Many covalently modified SUMO targets have been identified; however, the extent and significance of noncovalent interactions of SUMO with cellular proteins is poorly understood. Here, large-scale yeast two-hybrid screens repeatedly identified a surprisingly small number of proteins that interacted with three Arabidopsis SUMO isoforms. These SUMO-interacting proteins are nuclear and fall into two main categories: six histone or DNA methyltransferses or demethylases and six proteins that we show to be the evolutionary and functional homologs of SUMO-targeted ubiquitin ligases (STUbLs). The selectivity of the screen for several methylases and demethylases suggests that SUMO interaction with these proteins has a significant impact on chromatin methylation. Furthermore, the Arabidopsis STUbLs (AT-STUbLs) complemented to varying degrees the growth defects of the Schizosaccharomyces pombe STUbL mutant rfp1/rfp2, and three of them also complemented the genome integrity defects of this mutant, demonstrating that these proteins show STUbL activity. We show that one of the AT-STUbLs least related to the S. pombe protein, AT-STUbL4, has acquired a plant-specific function in the floral transition. It reduces protein levels of CYCLING DOF FACTOR 2, hence increasing transcript levels of CONSTANS and promoting flowering through the photoperiodic pathway.
authors.affiliation: Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Cologne 50829, Germany.
authors.forename: Nabil
authors.initials: N
authors.lastname: Elrouby
authors.forename: Mitzi Villajuana
authors.initials: MV
authors.lastname: Bonequi
authors.forename: Aimone
authors.initials: A
authors.lastname: Porri
authors.forename: George
authors.initials: G
authors.lastname: Coupland
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D015723:Gene Library; D008745:Methylation; D009687:Nuclear Proteins / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002843:Chromatin; D017931:DNA Primers; D009687:Nuclear Proteins; C403233:SUMO protein, plant; D014452:Ubiquitins
keywords: CDF; Flowering time; Nucleolus; SIM; Slx5/Slx8