title: A barrier-only boundary element delimits the formation of facultative heterochromatin in Drosophila melanogaster and vertebrates.
abstract: Formation of facultative heterochromatin at specific genomic loci is fundamentally important in defining cellular properties such as differentiation potential and responsiveness to developmental, physiological, and environmental stimuli. By the nature of their formation, heterochromatin and repressive histone marks propagate until the chain reaction is broken. While certain active promoters can block propagation of heterochromatin, there are also specialized DNA elements, referred to as chromatin barriers, that serve to demarcate the boundary of facultative heterochromatin formation. In this study, we identified a chromatin barrier that specifically limits the formation of repressive chromatin to a distal enhancer region so that repressive histone modifications cannot reach the promoter and promoter-proximal enhancer regions of reaper. Unlike all of the known boundary elements identified for Drosophila melanogaster, this IRER (irradiation-responsive enhancer region) left barrier (ILB) does not exhibit enhancer-blocking activity. Not only has the ILB been conserved in different Drosophila species, it can also function as an effective chromatin barrier in vertebrate cells. This suggests that the mechanism by which it functions to spatially restrict the formation of repressive chromatin marked by trimethylated H3K27 has also been conserved widely during evolution.
authors.affiliation: Department of Molecular Genetics and Microbiology & UF Shands Cancer Center, University of Florida, Gainesville, FL 32610, USA.
authors.forename: Nianwei
authors.initials: N
authors.lastname: Lin
authors.forename: Xingguo
authors.initials: X
authors.lastname: Li
authors.forename: Kairong
authors.initials: K
authors.lastname: Cui
authors.forename: Iouri
authors.initials: I
authors.lastname: Chepelev
authors.forename: Feng
authors.initials: F
authors.lastname: Tie
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.forename: Guangyao
authors.initials: G
authors.lastname: Li
authors.forename: Peter
authors.initials: P
authors.lastname: Harte
authors.forename: Keji
authors.initials: K
authors.lastname: Zhao
authors.forename: Suming
authors.initials: S
authors.lastname: Huang
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
mesh_terms: D000818:Animals; D001483:Base Sequence; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D020868:Gene Silencing; D006570:Heterochromatin / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D006570:Heterochromatin; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C066381:ct protein, Drosophila; C086973:rpr protein, Drosophila