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Journal ArticleDOI

X-chromosome inactivation: counting, choice and initiation

TLDR
In many sexually dimorphic species, a mechanism is required to ensure equivalent levels of gene expression from the sex chromosomes, and in mammals, such dosage compensation is achieved by X-chromosome inactivation, a process that presents a unique medley of biological puzzles.
Abstract
In many sexually dimorphic species, a mechanism is required to ensure equivalent levels of gene expression from the sex chromosomes. In mammals, such dosage compensation is achieved by X-chromosome inactivation, a process that presents a unique medley of biological puzzles: how to silence one but not the other X chromosome in the same nucleus; how to count the number of X's and keep only one active; how to choose which X chromosome is inactivated; and how to establish this silent state rapidly and efficiently during early development. The key to most of these puzzles lies in a unique locus, the X-inactivation centre and a remarkable RNA — Xist — that it encodes.

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Epigenetic regulation of gene expression: how the genome integrates intrinsic and environmental signals

TL;DR: Advances in the understanding of the mechanism and role of DNA methylation in biological processes are reviewed, showing that epigenetic mechanisms seem to allow an organism to respond to the environment through changes in gene expression.
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Regulation of heterochromatic silencing and histone H3 lysine-9 methylation by RNAi.

TL;DR: It is proposed that double-stranded RNA arising from centromeric repeats targets formation and maintenance of heterochromatin through RNAi.
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Chromatin modification and epigenetic reprogramming in mammalian development

TL;DR: The regulation of higher-order chromatin structures by DNA methylation and histone modification is crucial for genome reprogramming during early embryogenesis and gametogenesis, and for tissue-specific gene expression and global gene silencing.
Journal ArticleDOI

Non-coding RNA genes and the modern RNA world.

TL;DR: Non-coding RNAs seem to be particularly abundant in roles that require highly specific nucleic acid recognition without complex catalysis, such as in directing post-transcriptional regulation of gene expression or in guiding RNA modifications.
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Role of histone H3 lysine 27 methylation in X inactivation.

TL;DR: It is demonstrated that transient recruitment of the Eed-Ezh2 complex to the inactive X chromosome (Xi) occurs during initiation of X inactivation in both extraembryonic and embryonic cells and is accompanied by H3-K27 methylation.
References
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Journal ArticleDOI

A member of the caudal family of homeobox genes maps to the X-inactivation centre region of the mouse and human X chromosomes

TL;DR: Another gene is described, Cdx4, a member of the caudal-related family of homeobox genes, which is located within the minimal region assigned to XIC in humans, and is the closest known gene to XIST in both mouse and human.
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Xist expression from an Xist YAC transgene carried on the mouse Y chromosome

TL;DR: The data suggest that sequences in the vicinity of Xist can initiate some of the features that are associated with the initiation process of X-inactivation.
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The Mouse Tsx Gene Is Expressed in Sertoli Cells of the Adult Testis and Transiently in Premeiotic Germ Cells during Puberty

TL;DR: Tsx is the first gene to show a pattern of germ cell expression that is apparently specific to the pubertal testis and supports the hypothesis that during the first wave of normal spermatogenesis, the advent of a late-stage cell type is responsible for extinguishing expression in sperMatogonia in normal adult testis.
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Further examination of the Xist promoter-switch hypothesis in X inactivation: evidence against the existence and function of a P(0) promoter.

TL;DR: Analysis of expression and half-life of Xist RNA produced from an Xist transgene lacking P(0) but retaining P(1) suggests that mechanisms other than switching of functionally distinct promoters control the up-regulation of Xists.
Journal ArticleDOI

Replication timing of the human X-inactivation center (XIC) region: correlation with chromosome bands

TL;DR: The human genome is composed of long-range G+C% mosaic structures, which are thought to be related to chromosome bands, and it is proposed that the 1Mb late-replicated zone (from the large inverted duplication to XIST) corresponds to a G-band Xq13.2.1.
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