title: Domains of heterochromatin protein 1 required for Drosophila melanogaster heterochromatin spreading.
abstract: Centric regions of eukaryotic genomes are packaged into heterochromatin, which possesses the ability to spread along the chromosome and silence gene expression. The process of spreading has been challenging to study at the molecular level due to repetitious sequences within centric regions. A heterochromatin protein 1 (HP1) tethering system was developed that generates "ectopic heterochromatin" at sites within euchromatic regions of the Drosophila melanogaster genome. Using this system, we show that HP1 dimerization and the PxVxL interaction platform formed by dimerization of the HP1 chromo shadow domain are necessary for spreading to a downstream reporter gene located 3.7 kb away. Surprisingly, either the HP1 chromo domain or the chromo shadow domain alone is sufficient for spreading and silencing at a downstream reporter gene located 1.9 kb away. Spreading is dependent on at least two H3K9 methyltransferases, with SU(VAR)3-9 playing a greater role at the 3.7-kb reporter and dSETDB1 predominately acting at the 1.9 kb reporter. These data support a model whereby HP1 takes part in multiple mechanisms of silencing and spreading.
authors.affiliation: Department of Biochemistry, University of Iowa, Iowa City, 52242, USA.
authors.forename: Karrie A
authors.initials: KA
authors.lastname: Hines
authors.forename: Diane E
authors.initials: DE
authors.lastname: Cryderman
authors.forename: Kaitlin M
authors.initials: KM
authors.lastname: Flannery
authors.forename: Hongbo
authors.initials: H
authors.lastname: Yang
authors.forename: Michael W
authors.initials: MW
authors.lastname: Vitalini
authors.forename: Tulle
authors.initials: T
authors.lastname: Hazelrigg
authors.forename: Craig A
authors.initials: CA
authors.lastname: Mizzen
authors.forename: Lori L
authors.initials: LL
authors.lastname: Wallrath
mesh_terms: D000818:Animals; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000502:physiology*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D020868:Gene Silencing; D017930:Genes, Reporter; D006570:Heterochromatin / Q000378:metabolism*; D008722:Methods; D008780:Methyltransferases; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; D006570:Heterochromatin; D000090266:Chromobox Protein Homolog 5; D008780:Methyltransferases