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Curr Biol. 2000 Nov 30;10(23):1531-4.

Higher concentrations of histone macroH2A in the Barr body are correlated with higher nucleosome density.

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Equipe, DyOGen, Institut Albert Bonniot, Faculté de Médecine, et Laboratoire de Biologie Moléculaire et Cellulaire de la Différenciation, INSERM U309, Domaine de la Merci, 38706,., La Tronche Cedex, France.


Histone macroH2A, which is a subtype of histone H2A, possesses a histone H2A-like portion fused to a relatively long non-histone portion. MacroH2A has been shown to associate preferentially with the inactive X chromosome [1]. To investigate the specificity of this association, the nuclear distribution of macroH2A was compared with that of regular core histones. In normal human female fibroblasts, all anti-histone antibodies that were tested (including anti-macroH2A antibody) preferentially labeled the inactive X chromosome. Moreover, when expressed as green fluorescent protein (GFP) fusions, both histone H2A and macroH2A were concentrated in the Barr body. These data clearly show the presence of a higher density of nucleosomes in the inactive X chromosome. Accordingly, the specificity of the macroH2A association with the inactive X chromosome should be reconsidered. While investigating the role of macroH2A, we found that the proximity of the non-histone region of macroH2A to a promoter could lead to a specific repression of transcription, suggesting that the incorporation of macroH2A into chromatin might help to establish the stable pattern of gene expression in differentiated cells.

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