Enrichment profiles of Ser-5 phosphorylated RNA polymerase II (PolII S5p) in mouse female ES cells
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ABSTRACT: Many animal species employ a chromosome-based mechanism of sex determination, which has led to coordinate evolution of dosage compensation systems. Dosage compensation not only corrects the imbalance in the number of X-chromosomes between the sexes, but is also hypothesized to correct dosage imbalance within cells due to mono-allelic X expression and bi-allelic autosomal expression, by upregulating X-linked genes (termed ‘Ohno’s hypothesis’). It is unknown whether any epigenetic mark or protein is involved in X upregulation in mammals. Ser-5 phosphorylated RNA polymerase II (PolII S5p) is required for transcription initiation. Chromatin immunoprecipitation combined with DNA tiling array analysis (ChIP-chip) of PolII S5p in mouse female ES cells with two active X chromosomes demonstrated a greater enrichment of RNA polymerase II on X-linked genes relative to autosomal genes, suggesting that enhanced transcription initiation may play a role in X upregulation. Comparison of RNA PolII S5p enrichment on the X versus autosomes in mouse
Project description:Many animal species employ a chromosome-based mechanism of sex determination, which has led to coordinate evolution of dosage compensation systems. Dosage compensation not only corrects the imbalance in the number of X-chromosomes between the sexes, but is also hypothesized to correct dosage imbalance within cells due to mono-allelic X expression and bi-allelic autosomal expression, by upregulating X-linked genes (termed M-bM-^@M-^XOhnoM-bM-^@M-^Ys hypothesisM-bM-^@M-^Y). To identify molecular mechanisms of X upregulation in mammals we established genome-wide profiles for the initiation and elongation forms of RNA polymerase II (PolII), PolII-S5p (phosphorylated at serine 5) and PolII-S2p (phosphorylated at serine 2), and for histone modifications in mouse cell lines and tissues. We found that in addition to being enriched in PolII-S5p but not in PolII-S2p, X-linked promoters were also enriched in two epigenetic marks, H4K16ac and H2AZ, dependent on expression levels. To address the function of the H4K16 acetyltransferase MOF occupancy profiles were established and knockdowns of MOF and MSL1 were done in mouse ES cells. Our results support a conserved role for the MSL complex to enhance transcription initiation of X-linked genes. Comparison of the profiles of RNA PolII, the H4K16ac acetyltransferase MOF and histone active marks on the X versus autosomes in mouse
Project description:Many animal species employ a chromosome-based mechanism of sex determination, which has led to coordinate evolution of dosage compensation systems. Dosage compensation not only corrects the imbalance in the number of X-chromosomes between the sexes, but is also hypothesized to correct dosage imbalance within cells due to mono-allelic X expression and bi-allelic autosomal expression, by upregulating X-linked genes (termed ‘Ohno’s hypothesis’). It is unknown whether any epigenetic mark or protein is involved in X upregulation in mammals. Ser-5 phosphorylated RNA polymerase II (PolII S5p) is required for transcription initiation. Chromatin immunoprecipitation combined with DNA tiling array analysis (ChIP-chip) of PolII S5p in mouse female ES cells with two active X chromosomes demonstrated a greater enrichment of RNA polymerase II on X-linked genes relative to autosomal genes, suggesting that enhanced transcription initiation may play a role in X upregulation.
Project description:Many animal species employ a chromosome-based mechanism of sex determination, which has led to coordinate evolution of dosage compensation systems. Dosage compensation not only corrects the imbalance in the number of X-chromosomes between the sexes, but is also hypothesized to correct dosage imbalance within cells due to mono-allelic X expression and bi-allelic autosomal expression, by upregulating X-linked genes (termed ‘Ohno’s hypothesis’). To identify molecular mechanisms of X upregulation in mammals we established genome-wide profiles for the initiation and elongation forms of RNA polymerase II (PolII), PolII-S5p (phosphorylated at serine 5) and PolII-S2p (phosphorylated at serine 2), and for histone modifications in mouse cell lines and tissues. We found that in addition to being enriched in PolII-S5p but not in PolII-S2p, X-linked promoters were also enriched in two epigenetic marks, H4K16ac and H2AZ, dependent on expression levels. To address the function of the H4K16 acetyltransferase MOF occupancy profiles were established and knockdowns of MOF and MSL1 were done in mouse ES cells. Our results support a conserved role for the MSL complex to enhance transcription initiation of X-linked genes.
Project description:Many animal species employ a chromosome-based mechanism of sex determination, which has led to coordinate evolution of dosage compensation systems. Dosage compensation not only corrects the imbalance in the number of X-chromosomes between the sexes, but is also hypothesized to correct dosage imbalance within cells due to mono-allelic X expression and bi-allelic autosomal expression, by upregulating X-linked genes (termed M-CM-"M-BM-^@M-BM-^XOhnoM-CM-"M-BM-^@M-BM-^Ys hypothesisM-CM-"M-BM-^@M-BM-^Y). Although this hypothesis is well supported by expression analyses of individual X-linked genes and by array-based transcriptome analyses, a recent study claimed that no such X upregulation exists in mammals and C. elegans based on RNA-sequencing and proteomics analyses. We provide RNA-seq RNA-seq analysis of mouse female PGK12.1 ES cells with two active X chromosomes and confirmed that the X chromosome is upregulated, consistent with the previous microarray study. Examination of expression of X-linked and autosomal genes in mouse female ES cells with two active X chromosomes.
Project description:Many animal species employ a chromosome-based mechanism of sex determination, which has led to coordinate evolution of dosage compensation systems. Dosage compensation not only corrects the imbalance in the number of X-chromosomes between the sexes, but is also hypothesized to correct dosage imbalance within cells due to mono-allelic X expression and bi-allelic autosomal expression, by upregulating X-linked genes (termed âOhnoâs hypothesisâ). Although this hypothesis is well supported by expression analyses of individual X-linked genes and by array-based transcriptome analyses, a recent study claimed that no such X upregulation exists in mammals and C. elegans based on RNA-sequencing and proteomics analyses. We provide RNA-seq RNA-seq analysis of mouse female PGK12.1 ES cells with two active X chromosomes and confirmed that the X chromosome is upregulated, consistent with the previous microarray study.
Project description:In mammals, genes located on the X chromosome are present in one copy in XY males and two in XX females. To balance the dosage of X-linked gene expression between the sexes one of the two X chromosomes in females is silenced by X inactivation initiated by up-regulation of the lncRNA (long non-coding RNA) Xist and recruitment of specific chromatin modifiers for silencing. The inactivated X chromosome becomes heterochromatic and visits a specific nuclear compartment adjacent to the nucleolus. We report a novel role for the X-linked lncRNA Firre in anchoring the inactive mouse X chromosome and preserving one of its main epigenetic features, trimethylation of histone H3 at lysine 27 (H3K27me3). Similar to Dxz4, Firre is expressed from a macrosatellite repeat locus associated with a cluster of CTCF and cohesin binding specifically on the inactive X. CTCF binding initially present in both male and female mouse embryonic stem cells was found to be lost from the active X during development. The Firre and Dxz4 loci on the inactive X were preferentially located adjacent to the nucleolus. Knockdown of Firre RNA disrupted perinucleolar targeting and H3K27me3 levels in mouse fibroblasts, demonstrating an important role for this lncRNA in maintenance of one of the main epigenetic features of the X chromosome. There was no X-linked gene reactivation after Firre knockdown; however, a compensatory increase in the expression of chromatin modifier genes implicated in X silencing was observed. In female ES cells Firre RNA knockdown did not disrupt Xist expression/coating nor silencing of G6pdx during differentiation, suggesting that Firre does not play a role in the onset of X inactivation. We conclude that the X-linked lncRNA Firre helps position the inactive X chromosome near the nucleolus and preserve one of its main epigenetic features. Examination of allelic protein-binding or histone modification profiles in Patski cells.
Project description:We report the application of single-molecule-based sequencing technology for high-throughput profiling of RNA polymerase II phosphorylated at serine 5 (PolII-S5p; the transcription initiation form) in female mouse cultured hybrid cells and female hybrid brain derived from mouse systems with skewed X inactivation based on crosses between C57BL/6J (BL6) and M. spretus. In these systems, alleles can be differentiated by frequent SNPs between mouse species, and the active X (Xa) compared to the haploid set of autosomes from the same species. To examine PolII-S5p occupancy in vivo, ChIP-seq was done in brain from an adult female F1 mouse in which the BL6 X is always active and the spretus X inactive. Uniquely mapped reads containing informative SNPs were assigned to each haploid chromosome set (BL6 or spretus) and were counted to establish allele-specific PolII-S5p occupancy profiles. We found that PolII-S5p allele-specific occupancy with or without normalization by input genomic DNA sequencing data showed that expressed genes on the Xa (>1RPKM) had 30% higher PolII-S5p peak levels at their promoters compared to autosomal genes from the same species (BL6). This result was confirmed by performing an independent allele-specific ChIP-seq analysis on fibroblasts derived from embryonic kidney (Patski cell line) that have the opposite X inactivation pattern from the brain sample, i.e. an Xa from M. spretus and an Xi from BL6. These findings suggest that transcription initiation of X-linked genes is enhanced to contribute to X upregulation in cell lines and in vivo.
Project description:We report the application of single-molecule-based sequencing technology for high-throughput profiling of RNA polymerase II phosphorylated at serine 5 (PolII-S5p; the transcription initiation form) in female mouse cultured hybrid cells and female hybrid brain derived from mouse systems with skewed X inactivation based on crosses between C57BL/6J (BL6) and M. spretus. In these systems, alleles can be differentiated by frequent SNPs between mouse species, and the active X (Xa) compared to the haploid set of autosomes from the same species. To examine PolII-S5p occupancy in vivo, ChIP-seq was done in brain from an adult female F1 mouse in which the BL6 X is always active and the spretus X inactive. Uniquely mapped reads containing informative SNPs were assigned to each haploid chromosome set (BL6 or spretus) and were counted to establish allele-specific PolII-S5p occupancy profiles. We found that PolII-S5p allele-specific occupancy with or without normalization by input genomic DNA sequencing data showed that expressed genes on the Xa (>1RPKM) had 30% higher PolII-S5p peak levels at their promoters compared to autosomal genes from the same species (BL6). This result was confirmed by performing an independent allele-specific ChIP-seq analysis on fibroblasts derived from embryonic kidney (Patski cell line) that have the opposite X inactivation pattern from the brain sample, i.e. an Xa from M. spretus and an Xi from BL6. These findings suggest that transcription initiation of X-linked genes is enhanced to contribute to X upregulation in cell lines and in vivo. Examination of allele-specific PolII-S5p occupancy in mouse hybrid cells and brain.
Project description:Dosage compensation was referred as an equalized X chromosome gene expression between males and females in Drosophila. And inverse dosage effects, produced by genomic imbalance, are believed to account for this modulated expression. Here we made a global expression comparison of trisomy 2L with on extra copy of chromosome 2 long arm to normal diploid with two copies of 2L with high throughput RNA-sequencing. We want to test how about the gene expression pattern changes in those comparisons, including the genes on varied chromosome 2 long arm, some other autosomal genes except chromosome 2L and X chromosome genes. Dosage compensation with an expression level similar to normal diploid and inverse dosage effects should be detected.
Project description:Dosage compensation was referred as an equalized X chromosome gene expression between males and females in Drosophila. And inverse dosage effects, produced by genomic imbalance, are believed to account for this modulated expression. Here we made a global expression comparison of trisomy 2L with on extra copy of chromosome 2 long arm to normal diploid with two copies of 2L with high throughput RNA-sequencing. We want to test how about the gene expression pattern changes in those comparisons, including the genes on varied chromosome 2 long arm, some other autosomal genes except chromosome 2L and X chromosome genes. Dosage compensation with an expression level similar to normal diploid and inverse dosage effects should be detected. Comapare the global expression of trisomy 2L samples with the normal diploids Collected the females and males from trisomy 2L and Cantons and performed RNA-seq