Getting to the center of X-chromosome inactivation: the role of transgenes.
X-chromosome inactivation is a fascinating epigenetic phenomenon that is initiated by expression of a noncoding (nc)RNA, XIST, and results in transcriptional silencing of 1 female X. The process requires a series of events that begins even before XIST expression, and culminates in an active and a silent X within the same nucleus. We will focus on the role that transgenic systems have served in the current understanding of the process of X-chromosome inactivation, both in the initial delineation of an active and inactive X, and in the function of the XIST RNA. X inactivation is strictly cis-limited; recent studies have revealed elements within the X-inactivation center, the region required for inactivation, that are critical for the initial regulation of Xist expression and chromosome pairing. It has been revealed that the X-inactivation center contains a remarkable compendium of cis-regulatory elements, ncRNAs, and trans-acting pairing regions. We review the functional componentry of the X-inactivation center and discuss experiments that helped to dissect the XIST/Xist RNA and its involvement in the establishment of facultative heterochromatin.
Minks
Jakub
J
Molecular Epigenetics Group, Department of Medical Genetics, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T1Z3, Canada.
Brown
Carolyn J
CJ
D000818:Animals; D006801:Humans; D008954:Models, Biological; D022661:RNA, Untranslated / Q000502:physiology; D050436:Regulatory Elements, Transcriptional / Q000502:physiology; D019076:Transgenes / Q000502:physiology*; D014960:X Chromosome / Q000737:chemistry / Q000235:genetics; D049951:X Chromosome Inactivation / Q000235:genetics* / Q000502:physiology*
D022661:RNA, Untranslated