title: Insulator protein Su(Hw) recruits SAGA and Brahma complexes and constitutes part of Origin Recognition Complex-binding sites in the Drosophila genome.
abstract: Despite increasing data on the properties of replication origins, molecular mechanisms underlying origin recognition complex (ORC) positioning in the genome are still poorly understood. The Su(Hw) protein accounts for the activity of best-studied Drosophila insulators. Here, we show that Su(Hw) recruits the histone acetyltransferase complex SAGA and chromatin remodeler Brahma to Su(Hw)-dependent insulators, which gives rise to regions with low nucleosome density and creates conditions for ORC binding. Depletion in Su(Hw) leads to a dramatic drop in the levels of SAGA, Brahma and ORC subunits and a significant increase in nucleosome density on Su(Hw)-dependent insulators, whereas artificial Su(Hw) recruitment itself is sufficient for subsequent SAGA, Brahma and ORC binding. In contrast to the majority of replication origins that associate with promoters of active genes, Su(Hw)-binding sites constitute a small proportion (6%) of ORC-binding sites that are localized preferentially in transcriptionally inactive chromatin regions termed BLACK and BLUE chromatin. We suggest that the key determinants of ORC positioning in the genome are DNA-binding proteins that constitute different DNA regulatory elements, including insulators, promoters and enhancers. Su(Hw) is the first example of such a protein.
authors.affiliation: Department of Transcriptional Regulation and Chromatin Dynamics, Institute of Gene Biology, Russian Academy of Sciences, Moscow, 119334, Russia.
authors.forename: Nadezhda E
authors.initials: NE
authors.lastname: Vorobyeva
authors.forename: Marina U
authors.initials: MU
authors.lastname: Mazina
authors.forename: Anton K
authors.initials: AK
authors.lastname: Golovnin
authors.forename: Daria V
authors.initials: DV
authors.lastname: Kopytova
authors.forename: Dmitriy Y
authors.initials: DY
authors.lastname: Gurskiy
authors.forename: Elena N
authors.initials: EN
authors.lastname: Nabirochkina
authors.forename: Sofia G
authors.initials: SG
authors.lastname: Georgieva
authors.forename: Pavel G
authors.initials: PG
authors.lastname: Georgiev
authors.forename: Aleksey N
authors.initials: AN
authors.lastname: Krasnov
mesh_terms: D000818:Animals; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D042002:Chromatin Assembly and Disassembly; D004330:Drosophila / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D049750:Genome, Insect; D006609:High Mobility Group Proteins / Q000378:metabolism; D051548:Histone Acetyltransferases / Q000378:metabolism*; D038101:Insulator Elements; D009707:Nucleosomes / Q000378:metabolism; D051738:Origin Recognition Complex / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: C427488:BAP111 protein, Drosophila; C547399:Cdc45 protein, Drosophila; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D006609:High Mobility Group Proteins; D009707:Nucleosomes; D051738:Origin Recognition Complex; D012097:Repressor Proteins; D015534:Trans-Activators; C086469:brm protein, Drosophila; C083738:su(Hw) protein, Drosophila; D051548:Histone Acetyltransferases