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Developmentally regulated alterations in Polycomb repressive complex 1 proteins on the inactive X chromosome.

Plath K, Talbot D, Hamer KM, Otte AP, Yang TP, Jaenisch R, Panning B - J. Cell Biol. (2004)

Bottom Line: In this study, we demonstrate that mPRC1 proteins localize to the Xi, and that different mPRC1 proteins accumulate on the Xi during initiation and maintenance of X inactivation in embryonic cells.The Xi accumulation of mPRC1 proteins requires Xist RNA and is not solely regulated by the presence of H3-K27 methylation, as not all cells that exhibit this epigenetic mark on the Xi show Xi enrichment of mPRC1 proteins.Our results implicate mPRC1 in X inactivation and suggest that the regulated assembly of PcG protein complexes on the Xi contributes to this multistep process.

View Article: PubMed Central - PubMed

Affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA. plath@wi.mit.edu

ABSTRACT
Polycomb group (PcG) proteins belonging to the polycomb (Pc) repressive complexes 1 and 2 (PRC1 and PRC2) maintain homeotic gene silencing. In Drosophila, PRC2 methylates histone H3 on lysine 27, and this epigenetic mark facilitates recruitment of PRC1. Mouse PRC2 (mPRC2) has been implicated in X inactivation, as mPRC2 proteins transiently accumulate on the inactive X chromosome (Xi) at the onset of X inactivation to methylate histone H3 lysine 27 (H3-K27). In this study, we demonstrate that mPRC1 proteins localize to the Xi, and that different mPRC1 proteins accumulate on the Xi during initiation and maintenance of X inactivation in embryonic cells. The Xi accumulation of mPRC1 proteins requires Xist RNA and is not solely regulated by the presence of H3-K27 methylation, as not all cells that exhibit this epigenetic mark on the Xi show Xi enrichment of mPRC1 proteins. Our results implicate mPRC1 in X inactivation and suggest that the regulated assembly of PcG protein complexes on the Xi contributes to this multistep process.

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Kinetics of Xi enrichment of mPRC1 proteins in differentiating ES cells. The proportion of differentiating female ES cells exhibiting Xi enrichment for Eed (a), Phc1 (b), Bmi-1 (c), Cbx2 (d), and Phc2 (e) were determined over an 11 d time course. At each time point the percentage of Xist RNA-coated Xis that exhibited enrichment for the PcG protein indicated was calculated. At day 0 >100 cells were assayed and Xi enrichment of Xist or mPRC1 proteins was not detected. At each time point after day 0, percentages are based on counts of between 100 and 750 nuclei that exhibited Xist RNA coating of the Xi.
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fig6: Kinetics of Xi enrichment of mPRC1 proteins in differentiating ES cells. The proportion of differentiating female ES cells exhibiting Xi enrichment for Eed (a), Phc1 (b), Bmi-1 (c), Cbx2 (d), and Phc2 (e) were determined over an 11 d time course. At each time point the percentage of Xist RNA-coated Xis that exhibited enrichment for the PcG protein indicated was calculated. At day 0 >100 cells were assayed and Xi enrichment of Xist or mPRC1 proteins was not detected. At each time point after day 0, percentages are based on counts of between 100 and 750 nuclei that exhibited Xist RNA coating of the Xi.

Mentions: The percentages of MEFs with Xi enrichment of mPRC1 proteins and the standard errors are based on counts of 100–400 cells in each of three to nine independent experiments similar to that shown in Fig. 1. Percentages of cells with mPRC1 Xi enrichment in differentiating ES cells and undifferentiated ES cells ectopically expressing Xist are taken from Figs. 5 and 6. The percentages of TS and 293 cells with Xi enrichment of PRC1 proteins are based on counts of >75 cells in each of two or more experiments similar to those displayed in Figs. 2 and 3. H3-3mK27 percentages in all cell types are based on counts of at least 100 cells in two or more experiments. In all cases, only interphase cells were counted.


Developmentally regulated alterations in Polycomb repressive complex 1 proteins on the inactive X chromosome.

Plath K, Talbot D, Hamer KM, Otte AP, Yang TP, Jaenisch R, Panning B - J. Cell Biol. (2004)

Kinetics of Xi enrichment of mPRC1 proteins in differentiating ES cells. The proportion of differentiating female ES cells exhibiting Xi enrichment for Eed (a), Phc1 (b), Bmi-1 (c), Cbx2 (d), and Phc2 (e) were determined over an 11 d time course. At each time point the percentage of Xist RNA-coated Xis that exhibited enrichment for the PcG protein indicated was calculated. At day 0 >100 cells were assayed and Xi enrichment of Xist or mPRC1 proteins was not detected. At each time point after day 0, percentages are based on counts of between 100 and 750 nuclei that exhibited Xist RNA coating of the Xi.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172612&req=5

fig6: Kinetics of Xi enrichment of mPRC1 proteins in differentiating ES cells. The proportion of differentiating female ES cells exhibiting Xi enrichment for Eed (a), Phc1 (b), Bmi-1 (c), Cbx2 (d), and Phc2 (e) were determined over an 11 d time course. At each time point the percentage of Xist RNA-coated Xis that exhibited enrichment for the PcG protein indicated was calculated. At day 0 >100 cells were assayed and Xi enrichment of Xist or mPRC1 proteins was not detected. At each time point after day 0, percentages are based on counts of between 100 and 750 nuclei that exhibited Xist RNA coating of the Xi.
Mentions: The percentages of MEFs with Xi enrichment of mPRC1 proteins and the standard errors are based on counts of 100–400 cells in each of three to nine independent experiments similar to that shown in Fig. 1. Percentages of cells with mPRC1 Xi enrichment in differentiating ES cells and undifferentiated ES cells ectopically expressing Xist are taken from Figs. 5 and 6. The percentages of TS and 293 cells with Xi enrichment of PRC1 proteins are based on counts of >75 cells in each of two or more experiments similar to those displayed in Figs. 2 and 3. H3-3mK27 percentages in all cell types are based on counts of at least 100 cells in two or more experiments. In all cases, only interphase cells were counted.

Bottom Line: In this study, we demonstrate that mPRC1 proteins localize to the Xi, and that different mPRC1 proteins accumulate on the Xi during initiation and maintenance of X inactivation in embryonic cells.The Xi accumulation of mPRC1 proteins requires Xist RNA and is not solely regulated by the presence of H3-K27 methylation, as not all cells that exhibit this epigenetic mark on the Xi show Xi enrichment of mPRC1 proteins.Our results implicate mPRC1 in X inactivation and suggest that the regulated assembly of PcG protein complexes on the Xi contributes to this multistep process.

View Article: PubMed Central - PubMed

Affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA. plath@wi.mit.edu

ABSTRACT
Polycomb group (PcG) proteins belonging to the polycomb (Pc) repressive complexes 1 and 2 (PRC1 and PRC2) maintain homeotic gene silencing. In Drosophila, PRC2 methylates histone H3 on lysine 27, and this epigenetic mark facilitates recruitment of PRC1. Mouse PRC2 (mPRC2) has been implicated in X inactivation, as mPRC2 proteins transiently accumulate on the inactive X chromosome (Xi) at the onset of X inactivation to methylate histone H3 lysine 27 (H3-K27). In this study, we demonstrate that mPRC1 proteins localize to the Xi, and that different mPRC1 proteins accumulate on the Xi during initiation and maintenance of X inactivation in embryonic cells. The Xi accumulation of mPRC1 proteins requires Xist RNA and is not solely regulated by the presence of H3-K27 methylation, as not all cells that exhibit this epigenetic mark on the Xi show Xi enrichment of mPRC1 proteins. Our results implicate mPRC1 in X inactivation and suggest that the regulated assembly of PcG protein complexes on the Xi contributes to this multistep process.

Show MeSH