title: Barring gene expression after XIST: maintaining facultative heterochromatin on the inactive X.
abstract: X chromosome inactivation refers to the developmentally regulated process of silencing gene expression from all but one X chromosome per cell in female mammals in order to equalize the levels of X chromosome derived gene expression between the sexes. While much attention has focused on the genetic and epigenetic events early in development that initiate the inactivation process, it is also important to understand the events that ensure maintenance of the inactive state through subsequent cell divisions. Gene silencing at the inactive X chromosome is irreversible in somatic cells and is achieved through the formation of facultative heterochromatin (visible as the Barr body) that is remarkably stable and faithfully preserved. Here we review the many features of inactive X chromatin in terminally differentiated cells and address the highly redundant mechanisms of maintaining the inactive X chromatin.
authors.affiliation: Department of Molecular Genetics & Microbiology, Institute for Genome Sciences and Policy, 103 Research Drive, Box 3382, Duke University Medical Center Durham, NC 27710, USA. chadw004@mc.duke.edu
authors.forename: Brian P
authors.initials: BP
authors.lastname: Chadwick
authors.forename: Huntington F
authors.initials: HF
authors.lastname: Willard
mesh_terms: D000818:Animals; D004303:Dosage Compensation, Genetic; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007399:Interphase / Q000235:genetics; D051379:Mice; D009707:Nucleosomes / Q000235:genetics / Q000378:metabolism; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics* / Q000378:metabolism; D012728:Sex Chromatin / Q000235:genetics / Q000378:metabolism*; D014960:X Chromosome / Q000235:genetics* / Q000378:metabolism*
chemical_list: D009707:Nucleosomes; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; C077885:XIST non-coding RNA