Sequence logic at enhancers governs a dual mechanism of endodermal organ fate induction by FOXA pioneer factors
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PROVIDER: PRJNA624086 | ENA |
REPOSITORIES: ENA
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Project description:FOXA pioneer transcription factors (TFs) associate with primed enhancers in endodermal organ precursors. Using a human stem cell model of pancreas differentiation, we here discover that only a subset of pancreatic enhancers is FOXA-primed, whereas the majority is unprimed and engages FOXA upon lineage induction. Primed enhancers are enriched for signal-dependent TF motifs and harbor abundant and strong FOXA motifs. Unprimed enhancers harbor fewer, more degenerate FOXA motifs, and FOXA recruitment to unprimed but not primed enhancers requires pancreatic TFs. Strengthening FOXA motifs at an unprimed enhancer near NKX6.1 renders FOXA recruitment pancreatic TF-independent, induces priming, and broadens the NKX6.1 expression domain. We make analogous observations about FOXA binding during hepatic and lung development. Our findings suggest a dual role for FOXA in endodermal organ development: First, FOXA facilitate signal-dependent lineage initiation via enhancer priming, and second, FOXA enforce organ cell type-specific gene expression via indirect recruitment by lineage-specific TFs.
2021-10-18 | GSE148368 | GEO
Project description: Not available
| S-EPMC8599738 | biostudies-literature
Project description:The FoxA family of pioneer transcription factors regulate hepatitis B virus (HBV) transcription, and hence viral replication. Hepatocyte-specific FoxA-deficiency in the HBV transgenic mouse model of chronic infection prevents the transcription of the viral DNA genome as a result of the failure of the developmentally controlled conversion of 5-methylcytosine residues to cytosine during postnatal hepatic maturation. These observations suggest that pioneer transcription factors such as FoxA, which mark genes for expression at subsequent developmental steps in the cellular differentiation program, mediate their effects by reversing the DNA methylation status of their target genes to permit their ensuing expression when the appropriate tissue-specific transcription factor combinations arise during development. Furthermore, as the FoxA-deficient HBV transgenic mice are viable, the specific developmental timing, abundance and isoform type of pioneer factor expression must permit all essential liver gene expression to occur at a level sufficient to support adequate liver function. This implies that pioneer transcription factors can recognize and mark their target genes in distinct developmental manners dependent upon, at least in part, the concentration and affinity of FoxA for its binding sites within enhancer and promoter regulatory sequence elements. This selective marking of cellular genes for expression by the FoxA pioneer factor compared to HBV may offer the opportunity for the specific silencing of HBV gene expression and hence the resolution of chronic HBV infections which annually are responsible for approximately one million deaths worldwide due to liver cirrhosis and hepatocellular carcinoma.
2017-02-16 | GSE89832 | GEO
Project description:Nuclear DNA is wrapped around core histones to form nucleosomes, which constrains how transcription factors bind to gene regulatory sequences. Pioneer transcription factors have the special ability to bind target DNA on nucleosomes and initiate gene regulatory events, often leading to a local opening of chromatin. Yet the nucleosomal configuration of such open chromatin and the basis for chromatin opening is unclear. Here we combine low and high levels of MNase digestion along with core histone ChIP-seq to assess the presence of nucleosomes at enhancers and promoters in mouse liver. We find that the pioneer factor FoxA displaces linker histone H1, thereby keeping enhancer nucleosomes accessible in chromatin and helping other transcription factors bind. MNase-accessible nucleosomes, bound by transcription factors, are retained substantially more at liver-specific enhancers than promoters and tissue-ubiquitous enhancers. Thus, nucleosomes are not exclusively repressive to gene regulation when they are retained with, and exposed by, pioneer factors.
2016-04-08 | GSE77670 | GEO
Project description:Tissue-specific DNA methylation patterns are created by transcription factors that recruit methylation and demethylation enzymes to cis-regulatory elements. To date, it is not known whether transcription factors are needed to continuously maintain methylation profiles in development and mature tissues or whether they only establish these marks during organ development. We queried the role of the pioneer factor FoxA in generating hypomethylated DNA at liver enhancers. We discovered a set of FoxA binding sites that undergo regional, FoxA-dependent demethylation during organ development. Conditional ablation of FoxA genes in the adult liver demonstrated that continued FoxA presence was not required to maintain the hypomethylated state, even when massive cell proliferation was induced. This study provides strong evidence for the stable, epigenetic nature of tissue-specific DNA methylation patterns directed by lineage-determining transcription factors during organ development.
2021-04-20 | GSE124384 | GEO
Project description:Converting epithelial into mesenchymal cells through epithelial-mesenchymal transition (EMT) requires massive changes in gene expression. How this is brought about is currently not clear. Here we examined the impact of the EMT master regulator SNAIL1 on the FOXA family of transcription factors which are distinguished by their particular competence to induce chromatin reorganization for the activation of transcriptional enhancer elements. We show that the expression of SNAIL1 and FOXA genes is anti-correlated in transcriptomes of colorectal tumors and cell lines. In two cellular EMT models, ectopically expressed Snail1 downregulates FOXA factors and directly represses FOXA1. To elucidate how FOXA factors contribute to the control of epithelial gene expression, we determined by ChIP-seq data analysis FOXA chromosomal distribution in relation to chromatin structural features characterizing distinct states of transcriptional activity. This revealed a preferential localization of FOXA1 and FOXA2 to transcriptional enhancers at signature genes that distinguish epithelial from mesenchymal colon tumors. To validate the significance of this association, we investigated the impact of FOXA factors on structure and function of transcriptional enhancers at the epithelial genes CDH1, CDX2 and EPHB3. Expression of dominant negative FOXA2 led to chromatin condensation at these enhancer elements. Site- directed mutagenesis of FOXA binding sites in reporter gene constructs and by genome- editing in situ impaired enhancer activity and completely abolished the active chromatin state of the EPHB3 enhancer. Conversely, expression of FOXA factors in cells with inactive CDX2 and EPHB3 enhancers led to chromatin opening and de novo deposition of the H3K4me1 and H3K27ac marks. These findings establish the pioneer function of FOXA factors at enhancer regions of epithelial genes and demonstrate their essential role in maintaining enhancer structure and function. Thus, by repressing FOXA family members, Snail1 targets transcription factors at strategically important positions in gene-regulatory hierarchies which may facilitate transcriptional reprogramming during EMT.
2017-11-10 | GSE106073 | GEO
Project description:BRG1 governs Glucocorticoid Receptor interactions with chromatin and pioneer factors across the genome
| PRJNA447949 | ENA
Project description:The Pioneer Factor Hypothesis (PFH) states that pioneer factors (PFs) are a subclass of transcription factors (TFs) that bind to and open inaccessible sites and then recruit non-pioneer factors (nonPFs) that activate batteries of silent genes. We tested the PFH by expressing the endodermal PF FoxA1 and nonPF Hnf4a in K562 lymphoblast cells. While co-expression of FoxA1 and Hnf4a activated a burst of endoderm-specific gene expression, we found no evidence for functional distinction between these two TFs. When expressed independently, both TFs bound and opened inaccessible sites, activated endodermal genes, and “pioneered” for each other, although FoxA1 required fewer copies of its motif to bind at inaccessible sites. A subset of targets required both TFs, but the mode of action at these targets did not conform to the sequential activity predicted by the PFH. From these results we propose an alternative to the PFH where “pioneer activity” depends not on the existence of discrete TF subclasses, but on TF binding affinity and genomic context.
2021-08-18 | GSE182190 | GEO
Project description:The Pioneer Factor Hypothesis (PFH) states that pioneer factors (PFs) are a subclass of transcription factors (TFs) that bind to and open inaccessible sites and then recruit non-pioneer factors (nonPFs) that activate batteries of silent genes. We tested the PFH by expressing the endodermal PF FoxA1 and nonPF Hnf4a in K562 lymphoblast cells. While co-expression of FoxA1 and Hnf4a activated a burst of endoderm-specific gene expression, we found no evidence for functional distinction between these two TFs. When expressed independently, both TFs bound and opened inaccessible sites, activated endodermal genes, and “pioneered” for each other, although FoxA1 required fewer copies of its motif to bind at inaccessible sites. A subset of targets required both TFs, but the mode of action at these targets did not conform to the sequential activity predicted by the PFH. From these results we propose an alternative to the PFH where “pioneer activity” depends not on the existence of discrete TF subclasses, but on TF binding affinity and genomic context.
2021-08-18 | GSE182189 | GEO
Project description:The Pioneer Factor Hypothesis (PFH) states that pioneer factors (PFs) are a subclass of transcription factors (TFs) that bind to and open inaccessible sites and then recruit non-pioneer factors (nonPFs) that activate batteries of silent genes. We tested the PFH by expressing the endodermal PF FoxA1 and nonPF Hnf4a in K562 lymphoblast cells. While co-expression of FoxA1 and Hnf4a activated a burst of endoderm-specific gene expression, we found no evidence for functional distinction between these two TFs. When expressed independently, both TFs bound and opened inaccessible sites, activated endodermal genes, and “pioneered” for each other, although FoxA1 required fewer copies of its motif to bind at inaccessible sites. A subset of targets required both TFs, but the mode of action at these targets did not conform to the sequential activity predicted by the PFH. From these results we propose an alternative to the PFH where “pioneer activity” depends not on the existence of discrete TF subclasses, but on TF binding affinity and genomic context.
2021-08-18 | GSE182188 | GEO