title: The PHD domain of plant PIAS proteins mediates sumoylation of bromodomain GTE proteins.
abstract: Covalent attachment of small ubiquitin-like modifier (SUMO) to proteins regulates multiple processes in the eukaryotic cell. In numerous cases sumoylation is facilitated by protein inhibitor of activated STAT (PIAS) proteins, characterized by the presence of a SP-RING domain related to the RING finger of many ubiquitin E3 ligases. The importance of SP-RING relies on its capacity to bind the E2 enzyme of the pathway. Additional domains may participate in SUMO ligase function and target selection. We have studied the Arabidopsis SUMO ligase AtSIZ1, belonging to the PIAS family, and describe self-sumoylation and AtSIZ1-mediated sumoylation of the E2 enzyme AtSCE1 and GTE3, a bromodomain protein interacting with AtSIZ1. Modification of GTE3 modulates its capacity to bind acetyl-histone H3 in vitro. Interestingly, AtSIZ1, as other plant PIAS proteins, also includes a PHD domain. We found that the PHD domain binds AtSCE1 and contributes to the SUMO ligase function, being partially and absolutely required for AtSCE1 and GTE3 sumoylation, respectively. Based on the capacity of AtSCE1 and GTE3 to associate with both the PHD and SP-RING domains, we propose a model of interactions to explain AtSIZ1-mediated sumoylation of GTE3 and ligase function of the PHD domain.
authors.affiliation: Centro Andaluz de Biología Molecular y Medicina Regenerativa Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Seville, Spain. mario.garcia@cabimer.es
authors.forename: Mario
authors.initials: M
authors.lastname: Garcia-Dominguez
authors.forename: Rosana
authors.initials: R
authors.lastname: March-Diaz
authors.forename: Jose C
authors.initials: JC
authors.lastname: Reyes
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D050828:Protein Inhibitors of Activated STAT / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D050828:Protein Inhibitors of Activated STAT; C477512:SUM1 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases