Histone macroH2A1 is concentrated in the inactive X chromosome of female mammals

@article{Costanzi1998HistoneMI,
  title={Histone macroH2A1 is concentrated in the inactive X chromosome of female mammals},
  author={Carl Costanzi and John R. Pehrson},
  journal={Nature},
  year={1998},
  volume={393},
  pages={599-601}
}
In female mammals one of the X chromosomes is rendered almost completely transcriptionally inactive, to equalize expression of X-linked genes in males and females. The inactive X chromosome is distinguished from its active counterpart by its condensed appearance in interphase nuclei, late replication, altered DNA methylation, hypoacetylation of histone H4 (ref. 5), and by transcription of a large cis-acting nuclear RNA called Xist. Although it is believed that the inactivation process involves… 
Histone macroH 2 A 1 is concentrated in the inactive X chromosome of female preimplantation mouse embryos
X inactivation involves several changes in the structure or properties of the inactive X chromosome that are believed to play a role in the initiation and/or maintenance of transcriptional silencing
Jumping onto the X chromosome
TLDR
Observations indicate that accumulation of macroH2A1.2 on the inactive X chromosome is not required for initiation or propagation of X inactivation, and the timing of this redistribution is highly synchronized, indicating a tightly regulated mechanism of disassembly.
Histone variant macroH2A contains two distinct macrochromatin domains capable of directing macroH2A to the inactive X chromosome
TLDR
This work has identified two macrochromatin domains within macroH2A that are independently capable of MCB formation and association with the Xi, indicating that the histone portion alone can target the Xi.
Histone Macroh2a1.2 Relocates to the Inactive X Chromosome after Initiation and Propagation of X-Inactivation
TLDR
The timing of macroH2A1.2 accumulation on the Xi suggests it is not necessary for the initiation or propagation of random X-inactivation, indicating a precisely regulated association.
MacroH2A1.2 binds the nuclear protein Spop.
Histone macroH2A1 is concentrated in the inactive X chromosome of female preimplantation mouse embryos.
TLDR
Of the changes that are known to happen during X inactivation in preimplantation embryos, the accumulation of macroH2A1 appears to be the earliest marker of the inactive X chromosome and is the only change that has been shown to occur during the period when transcriptional silencing is initiated.
Histone modification and the epigenetics of X chromosome inactivation
Dosage compensation serves to equalise the levels of X-linked gene products between males and females. In mammals this occurs through the transcriptional silencing of the majority of the genes on one
Histone H3 Lysine 9 Methylation Occurs Rapidly at the Onset of Random X Chromosome Inactivation
TLDR
It is shown that H3-K9 methylation is a very early event in the process of X inactivation, which closely parallels the onset of Xist RNA accumulation.
A Novel Chromatin Protein, Distantly Related to Histone H2a, Is Largely Excluded from the Inactive X Chromosome
TLDR
Separation of micrococcal nuclease–digested chromatin by sucrose gradient ultracentrifugation shows cofractionation of H2A-Bbd with nucleosomes, supporting the idea that H2Bbd is incorporated into nucleosome as a substitute for the core histone H2a.
Beyond the Xi
TLDR
New clues are provided into how mH2A distribution and a previously unidentified post-translational modification may help regulate the repression of autosomal chromatin.
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References

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The inactive X chromosome in female mammals is distinguished by a lack of histone H4 acetylation, a cytogenetic marker for gene expression
TLDR
It is proposed that H4 hyperacetylation defines regions of the genome containing potentially transcriptionally active chromatin, while virtual absence of H4 acetylation defined both constitutive and facultative heterochromatin.
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TLDR
The definition of a major role for Xist, a noncoding RNA, in X-inactivation has enabled investigation of the mechanism leading to establishment of the heterochromatinized X-chromosome and also of the interactions between X- inactivation and imprinting as well as between X -inactivation and developmental processes in the early embryo.
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TLDR
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TLDR
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TLDR
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TLDR
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TLDR
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TLDR
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TLDR
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TLDR
Analysis of the transcriptional activity of a number of X-linked genes in mouse/human somatic cell hybrids retaining an intact human inactive X chromosome or derivatives of the inactive X chromosomes lacking the XIC demonstrates that the presence of theXIC is not required for the maintenance of X inactivation in somatic cells.
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