Project description:We report the occupancy of GATA1 and TAL1, two erythroid transcription factors, and H3K27ac histone modification in human erythroid precursors.
Project description:We report a computational approach for investigation of chromatin state plasticity. We applied this approach to investigate an ENCODE ChIP-seq dataset profiling the genome-wide distribution of H3K27me3 in 19 human cell lines. We found that high plasticity regions (HPRs) can be divided into two functionally and mechanistically distinct groups, consisting of CpG island proximal and distal regions. We identified cell-type specific regulators correlating with H3K27me3 patterns at distal HPRs in ENCODE cell lines. Furthermore, we applied this approach to investigate mechanisms for poised enhancer establishment in primary human erythroid precursors. We predicted and validated a previously unrecognized role of TAL1 in modulating H3K27me3 patterns through interaction with additional cofactors, such as GFI1B. Our integrative approach provides mechanistic insights into chromatin state plasticity and is broadly applicable to other epigenetic marks. Analysis of genomic occupancy of H3K27me3, H3K27ac, GATA1, TAL1/SCL and GFI1B in primary adult human proerythroblasts by ChIP-seq.
Project description:The ability to measure epigenetic features, such as histone modifications and occupancy by transcription factors and co-activators, on a genome-wide scale is advancing the accuracy of CRM predictions. While integration of signals from multiple features is expected to improve predictions, the contribution of each feature to prediction accuracy is not known. We began with predictions of 4,915 erythroid enhancers based on genomic occupancy by TAL1, a key hematopoietic transcription factor that is strongly associated with gene induction in erythroid cells. Seventy of these DNA segments occupied by TAL1 (TAL1 OSs) were tested by transient transfections of cultured hematopoietic cells, and 56% of these were active as enhancers. Sixty-six TAL1 OSs were evaluated in transgenic mouse embryos, and 65% of these were active enhancers in various tissues. Inclusion of additional epigenetic features improved the prediction accuracy, with combinations of TAL1, GATA1, EP300, H3K4me1, and H3K27ac giving high accuracy of enhancer prediction (70%-75% success depending on method of clustering) while maintaining good sensitivity and specificity. Motifs that distinguish active from inactive TAL1 OSs implicate IRFs, STATs, and FOX protein families as candidate positive co-factors with TAL1, while REST (NRSF) and HOX family proteins are implicated in inactivity. While signals for evolutionary constraint were weak over the entire TAL1-bound DNA segments regardless of activity in either assay, phylogenetic preservation of a TF-binding site motif was associated with enhancer activity. The contribution of 8 epigenetic features including H3K27ac to identification of enhancers in 24h-induced G1E-ER4 cells.
Project description:We used mouse ENCODE data along with complementary data from other laboratories to study the dynamics of occupancy and the role in gene regulation of the transcription factor TAL1, a critical regulator of hematopoiesis, at multiple stages of hematopoietic differentiation. We combined ChIP-seq and RNA-seq data in six mouse cell types representing a progression from multilineage precursors to differentiated erythroblasts and megakaryocytes. We found that sites of occupancy shift dramatically during commitment to the erythroid lineage, vary further during terminal maturation, and are strongly associated with changes in gene expression. In multilineage progenitors, the likely target genes are enriched for hematopoietic growth and functions associated with the mature cells of specific daughter lineages (such as megakaryocytes). In contrast, target genes in erythroblasts are specifically enriched for red cell functions. Furthermore, shifts in TAL1 occupancy during erythroid differentiation are associated with gene repression (dissociation) and induction (co-occupancy with GATA1). Based on both enrichment for transcription factor binding site motifs and co-occupancy determined by ChIP-seq, recruitment by GATA transcription factors appears to be a stronger determinant of TAL1 binding to chromatin than the canonical E-box binding site motif. Studies of additional proteins lead to the model that TAL1 regulates expression after being directed to a distinct subset of genomic binding sites in each cell type via its association with different complexes containing master regulators such as GATA2, ERG, and RUNX1 in multilineage cells and the lineage-specific master regulator GATA1 in erythroblasts. Combined ChIP-seq and RNA-seq data in six mouse cell types representing a progression from multilineage precursors to differentiated erythroblasts and megakaryocytes.
Project description:We report the comparative investigation of genome-wide chromatin state maps, transcription factor (TF) occupancy, and gene expression profiles from developing red cell precursors at two developmental stages. Contrasting the similarities and differences between fetal and adult erythropoiesis provides important insights into the erythroid gene expression programs and gene regulatory networks. Specifically, comparative analyses of human erythropoiesis identify developmental stage-specific enhancers as primary determinants of stage-specific gene expression programs. We find that master regulators, such as GATA1 and TAL1, cooperatively act within active enhancers but have little predictive value for stage-specific enhancer activity. Instead, a set of stage-specific co-regulators collaborates with master regulators and contributes to differential gene expression. We further identify and validate IRF2, IRF6, and MYB as effectors of adult-stage expression program. Thus, the combinatorial assembly of master regulators and transcriptional co-regulators at developmental stage-specific enhancers controls gene expression programs and temporal regulation of transcriptional networks in a mammalian genome. Examination of various histone modifications and transcription factor occupancy by ChIP-seq in fetal and adult proerythroblasts.
Project description:Erythroid development and differentiation from multiprogenitor cells to red blood cells requires precise transcriptional regulation. Key erythroid transcription factors, GATA1 and TAL1, co-operate, along with other proteins, to regulate many aspects of this process. How GATA1 and TAL1 are positionally organized with respect to each other and their cognate DNA binding site across the mouse genome remains unclear. We applied high resolution ChIP-exo to GATA1 and TAL1 to study their positional organization across the mouse genome during GATA1-dependent maturation. Two complementary methods, MultiGPS and peak-pairing, were used to determine high confidence binding locations by ChIP-exo. We identified ~10,000 GATA1 and ~15,000 TAL1 locations, which were essentially confirmed by ChIP-seq. Of these, ~4,000 locations were bound by both GATA1 and TAL1. About three-quarters of these were tightly linked (<40 bp away) to a partial E-box located 7-8 bp upstream of a WGATAA motif. Both TAL1 and GATA1 generated distinct characteristic ChIP-exo peaks around WGATAA motifs, that reflect on their positional arrangement within a complex. We show that TAL1 and GATA1 form a precisely organized complex at a compound motif consisting of a TG 7-8 bp upstream of a WGATAA motif across thousands of genomic locations. Genome wide analysis of GATA1 and TAL1 in G1E and G1E-ER4 cells using ChIP-exo experiments
Project description:We used mouse ENCODE data along with complementary data from other laboratories to study the dynamics of occupancy and the role in gene regulation of the transcription factor TAL1, a critical regulator of hematopoiesis, at multiple stages of hematopoietic differentiation. We combined ChIP-seq and RNA-seq data in six mouse cell types representing a progression from multilineage precursors to differentiated erythroblasts and megakaryocytes. We found that sites of occupancy shift dramatically during commitment to the erythroid lineage, vary further during terminal maturation, and are strongly associated with changes in gene expression. In multilineage progenitors, the likely target genes are enriched for hematopoietic growth and functions associated with the mature cells of specific daughter lineages (such as megakaryocytes). In contrast, target genes in erythroblasts are specifically enriched for red cell functions. Furthermore, shifts in TAL1 occupancy during erythroid differentiation are associated with gene repression (dissociation) and induction (co-occupancy with GATA1). Based on both enrichment for transcription factor binding site motifs and co-occupancy determined by ChIP-seq, recruitment by GATA transcription factors appears to be a stronger determinant of TAL1 binding to chromatin than the canonical E-box binding site motif. Studies of additional proteins lead to the model that TAL1 regulates expression after being directed to a distinct subset of genomic binding sites in each cell type via its association with different complexes containing master regulators such as GATA2, ERG, and RUNX1 in multilineage cells and the lineage-specific master regulator GATA1 in erythroblasts.
Project description:To determine hemogen function in regulatory elements, ChIPmentation was performed in both WT and hemogen KO K562 cells and H3K27ac enrichment was significantly reduced at both promoters and enhancers in loss of hemogen. To identify direct targets and the regulatory role of hemogen in murine erythroid gene expression, hemogen and BRG1 ChIP-seq was performed in the WT and hemogen KO E14.5 fetal liver cells. Hemogen was found enriched in GATA1/TAL1 binding motifs and equally bind to the promoter and potential enhancer region. Notably, BRG1 occupancy (95%) was almost completely coincident with hemogen binding sites and loss of hemogen greatly impaired the BRG1 occupancy at both erythroid promoters and enhancers.
Project description:The ability to measure epigenetic features, such as histone modifications and occupancy by transcription factors and co-activators, on a genome-wide scale is advancing the accuracy of CRM predictions. While integration of signals from multiple features is expected to improve predictions, the contribution of each feature to prediction accuracy is not known. We began with predictions of 4,915 erythroid enhancers based on genomic occupancy by TAL1, a key hematopoietic transcription factor that is strongly associated with gene induction in erythroid cells. Seventy of these DNA segments occupied by TAL1 (TAL1 OSs) were tested by transient transfections of cultured hematopoietic cells, and 56% of these were active as enhancers. Sixty-six TAL1 OSs were evaluated in transgenic mouse embryos, and 65% of these were active enhancers in various tissues. Inclusion of additional epigenetic features improved the prediction accuracy, with combinations of TAL1, GATA1, EP300, H3K4me1, and H3K27ac giving high accuracy of enhancer prediction (70%-75% success depending on method of clustering) while maintaining good sensitivity and specificity. Motifs that distinguish active from inactive TAL1 OSs implicate IRFs, STATs, and FOX protein families as candidate positive co-factors with TAL1, while REST (NRSF) and HOX family proteins are implicated in inactivity. While signals for evolutionary constraint were weak over the entire TAL1-bound DNA segments regardless of activity in either assay, phylogenetic preservation of a TF-binding site motif was associated with enhancer activity.