title: SUMO conjugation is required for the assembly of Drosophila Su(Hw) and Mod(mdg4) into insulator bodies that facilitate insulator complex formation.
abstract: Chromatin insulators are special regulatory elements involved in modulation of enhancer-promoter interactions. The best studied insulators in Drosophila require Suppressor of Hairy Wing [Su(Hw)], Modifier of mdg4 [Mod(mdg4)] and centrosomal 190 kDa (CP190) proteins to be functional. These insulator proteins are colocalized in nuclear speckles named insulator bodies. Here, we demonstrate that post-translational modification of insulator proteins by small ubiquitin-like modifier (SUMO) and intact CP190 protein is crucial for insulator body formation. Inactivation of SUMO binding sites in Mod(mdg4)-67.2 leads to the inability of the mutant protein and Su(Hw) to be assembled into insulator bodies. In vivo functional tests show that a smaller amount of intact Mod(mdg4)-67.2, compared with the mutant protein, is required to restore the normal activity of the Su(Hw) insulator. However, high expression of mutant Mod(mdg4)-67.2 completely rescues the insulator activity, indicating that sumoylation is not necessary for enhancer blocking. These results suggest that insulator bodies function as a depot of sumoylated proteins that are involved in insulation and can facilitate insulator complex formation, but are nonessential for insulator action.
authors.affiliation: Department of Molecular Genetics of Drosophila, Russian Academy of Sciences, Moscow 119334, Russia. agolovnin@mail.ru
authors.forename: Anton
authors.initials: A
authors.lastname: Golovnin
authors.forename: Ilya
authors.initials: I
authors.lastname: Volkov
authors.forename: Pavel
authors.initials: P
authors.lastname: Georgiev
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D038101:Insulator Elements; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism*; D058207:Sumoylation; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C107964:CP190 protein, Drosophila; D029721:Drosophila Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D025842:SUMO-1 Protein; D014157:Transcription Factors; C101384:mod(mdg4) protein, Drosophila; C083738:su(Hw) protein, Drosophila