title: Chromatin boundaries require functional collaboration between the hSET1 and NURF complexes.
abstract: Chromatin insulators protect erythroid genes from being silenced during erythropoiesis, and the disruption of barrier insulator function in erythroid membrane gene loci results in mild or severe anemia. We showed previously that the USF1/2-bound 5'HS4 insulator mediates chromatin barrier activity in the erythroid-specific chicken β-globin locus. It is currently not known how insulators establish such a barrier. To understand the function of USF1, we purified USF1-associated protein complexes and found that USF1 forms a multiprotein complex with hSET1 and NURF, thus exhibiting histone H3K4 methyltransferase- and ATP-dependent nucleosome remodeling activities, respectively. Both SET1 and NURF are recruited to the 5'HS4 insulator by USF1 to retain the active chromatin structure in erythrocytes. Knock-down of NURF resulted in a rapid loss of barrier activity accompanied by an alteration of nucleosome positioning, increased occupancy of the nucleosome-free linker region at the insulator site, and increased repressive H3K27me3 levels in the vicinity of the HS4 insulator. Furthermore, suppression of SET1 reduced barrier activity, decreased H3K4me2 and acH3K9/K14, and diminished the recruitment of BPTF at several erythroid-specific barrier insulator sites. Therefore, our data reveal a synergistic role of hSET1 and NURF in regulating the USF-bound barrier insulator to prevent erythroid genes from encroachment of heterochromatin.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610, USA.
authors.forename: Xingguo
authors.initials: X
authors.lastname: Li
authors.forename: Shaohua
authors.initials: S
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Changwang
authors.initials: C
authors.lastname: Deng
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Steiner
authors.forename: Hua
authors.initials: H
authors.lastname: Xiao
authors.forename: Carl
authors.initials: C
authors.lastname: Wu
authors.forename: Jörg
authors.initials: J
authors.lastname: Bungert
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Gallagher
authors.forename: Gary
authors.initials: G
authors.lastname: Felsenfeld
authors.forename: Yi
authors.initials: Y
authors.lastname: Qiu
authors.forename: Suming
authors.initials: S
authors.lastname: Huang
mesh_terms: D000818:Animals; D002645:Chickens; D002843:Chromatin / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly / Q000235:genetics*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006367:HeLa Cells; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D038101:Insulator Elements / Q000502:physiology; D020014:K562 Cells; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D014407:Tumor Cells, Cultured; D051720:Upstream Stimulatory Factors / Q000378:metabolism
chemical_list: D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D046912:Multiprotein Complexes; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors; D011495:Histone-Lysine N-Methyltransferase; C526068:Setd1A protein, human