Intrinsic dynamics of an endogenous human gene reveal the basis of expression heterogeneity
Ontology highlight
ABSTRACT: Transcriptional regulation in metazoans occurs through long range genomic contacts between enhancers and promoters, and most genes are transcribed in episodic ‘bursts’ of RNA synthesis. The relationship between these two phenomena and the dynamic regulation of genes in response to upstream signals is unknown. Here, we describe the use of live-cell RNA imaging coupled with Hi-C measurements to dissect the regulation of the estrogen-responsive TFF1 gene under endogenous regulation. Although this gene is highly induced, we observe short active periods and variable inactive periods ranging from minutes to days. The heterogeneity in inactive times gives rise to the widely-observed ‘noise’ in human gene expression and explains the distribution of protein levels in human tissue. We derive a mathematical model of regulation that relates transcription, chromosome structure, and the cell’s ability to ‘sense’ changes in estrogen and predicts that hypervariability is largely dynamic and does not reflect a stable biological state.
Project description:Estrogen depletion in both rodents and humans leads to inactivity, unhealthy fat accumulation, and metabolic syndrome, underscoring the conserved metabolic benefits of estrogen signaling that inevitably decline with aging. Here, we uncover a hypothalamic node that integrates estrogen and melanocortin-4 receptor (MC4R) signaling to drive episodic bursts in activity prior to ovulation. Skirting the estrogen-dependent gating of this node by CRISPR activation of Mc4r reduces sedentary behavior long-term in both males and females. Our findings expand the impact of MC4R signaling beyond food intake regulation and rationalize reported sex-differences in melanocortin signaling including increased disease severity for women with MC4R-insuffciency. This newly identified hormone-dependent activity node illustrates the potency of estrogen in maintaining an active lifestyle.
Project description:Estrogen receptor-mediated proliferation of breast cancer cells is facilitated through expression of multiple primary target genes, products of which induce the secondary response to stimulation. To differentiate between the primary and secondary target genes of estrogen receptor signaling, we measured dynamics of protein expression induced by estradiol in MCF-7 breast cancer cells. Measurement of the global proteomic effects of estradiol by SILAC resulted in identification of 104 estradiol-regulated proteins, with only 41 corresponding genes having estrogen response elements (EREs). Selected reaction monitoring assays were used to validate 32 proteins and measure the dynamics of their expression within 72 hours upon estradiol stimulation and in the presence of 4-hydroxytamoxifen, thus confirming estrogen receptor-mediated signaling. Dynamics of protein expression revealed immediate early response proteins including TFF1 and CDK1 and delayed response proteins including CDK2 and NAB2. Presence or absence of EREs in the corresponding genes indicated early or delayed expression of proteins identified by SILAC. Finally, we measured accurate dynamics of estradiol-induced protein expression in the sub-network of primary and secondary targets of estrogen receptor. Interestingly, since NAB2 protein is also a repressor of EGR3-induced transcription, siRNA-mediated silencing of NAB2 resulted in the over-expression of some EGR3-induced proteins, such as ITGA2. To conclude, quantitative proteomics revealed secondary targets of estrogen receptor signaling potentially overlooked by genome-wide profiling of EREs and provided dynamics of protein expression in the network of transcription factors with a negative feedback loop.
Project description:Bleomycin (BLM) induces lung injury, leading to inflammation and pulmonary fibrosis. Regulatory T cells (Tregs) maintain self-tolerance and control host immune responses. However, little is known about their involvement in the pathology of pulmonary fibrosis. Here we show that a unique Treg subset that expresses trefoil factor family 1(Tff1) emerges in the BLM-injured lung. These Tff1-expressing Tregs (Tff1-Tregs) were induced by IL-33. Moreover, although Tff1 ablation in Tregs had no impact, selective ablation of Tff1-Tregs using an intersectional genetic method promoted pro-inflammatory features of macrophages in the injured lung and exacerbated the fibrosis. Taken together, our study revealed the presence of a unique Treg subset expressing Tff1 in BLM-injured lungs and their critical role in the injured lung to ameliorate fibrosis.
Project description:Bleomycin (BLM) induces lung injury, leading to inflammation and pulmonary fibrosis. Regulatory T cells (Tregs) maintain self-tolerance and control host immune responses. However, little is known about their involvement in the pathology of pulmonary fibrosis. Here we show that a unique Treg subset that expresses trefoil factor family 1(Tff1) emerges in the BLM-injured lung. These Tff1-expressing Tregs (Tff1-Tregs) were induced by IL-33. Moreover, although Tff1 ablation in Tregs had no impact, selective ablation of Tff1-Tregs using an intersectional genetic method promoted pro-inflammatory features of macrophages in the injured lung and exacerbated the fibrosis. Taken together, our study revealed the presence of a unique Treg subset expressing Tff1 in BLM-injured lungs and their critical role in the injured lung to ameliorate fibrosis.
Project description:Estrogen receptor M-NM-1 (ERM-NM-1) is a nuclear receptor that is the driving transcription factor expressed in the majority of breast cancers. Recent studies have demonstrated that the liver receptor homolog-1 (LRH-1), another nuclear receptor, is ERM-NM-1-regulated in breast cancer cells. Further, LRH-1 stimulates proliferation and promotes motility and invasion of breast cancer cells. To determine the mechanisms of LRH-1 action in breast cancer cells, we carried out gene expression microarray analysis following siRNA-mediated LRH-1 knockdown. Interestingly, gene ontology (GO) category enrichment analysis of the genes differentially regulated in the presence or absence of LRH-1 identified estrogen responsive genes as the most highly enriched GO categories. To further define LRH-1 target genes, we performed chromatin immunoprecipitation coupled to massively parallel sequencing (ChIP-seq) to identify genomic targets of LRH-1. Remarkably, ChIP-seq showed LRH-1 binding at many ERM-NM-1 binding sites. Analysis of select binding sites confirmed regulation of ERM-NM-1-regulated genes by LRH-1 through binding to estrogen response elements, as exemplified by the TFF1/pS2 gene. Finally, LRH-1 over-expression stimulated ERM-NM-1 recruitment, whilst LRH-1 knockdown reduced ERM-NM-1 recruitment to ERM-NM-1 binding sites. Taken together, our findings establish a key role for LRH-1 in the regulation of ERM-NM-1 target genes in breast cancer cells and identify a mechanism in which co-operative binding of LRH-1 and ERM-NM-1 at estrogen response elements controls the expression of estrogen-responsive genes. MCF-7 cells were transfected with LRH-1 siRNA #2, #3, or with a non-targeting siRNA (siControl) for 72 hours. Following assessment of RNA integrity, four biological replicates for each siRNA treatment were used for microarray analysis.
Project description:Estrogen receptor α (ERα) is a nuclear receptor that is the driving transcription factor expressed in the majority of breast cancers. Recent studies have demonstrated that the liver receptor homolog-1 (LRH-1), another nuclear receptor, is ERα-regulated in breast cancer cells. Further, LRH-1 stimulates proliferation and promotes motility and invasion of breast cancer cells. To determine the mechanisms of LRH-1 action in breast cancer cells, we carried out gene expression microarray analysis following siRNA-mediated LRH-1 knockdown. Interestingly, gene ontology (GO) category enrichment analysis of the genes differentially regulated in the presence or absence of LRH-1 identified estrogen responsive genes as the most highly enriched GO categories. To further define LRH-1 target genes, we performed chromatin immunoprecipitation coupled to massively parallel sequencing (ChIP-seq) to identify genomic targets of LRH-1. Remarkably, ChIP-seq showed LRH-1 binding at many ERα binding sites. Analysis of select binding sites confirmed regulation of ERα-regulated genes by LRH-1 through binding to estrogen response elements, as exemplified by the TFF1/pS2 gene. Finally, LRH-1 over-expression stimulated ERα recruitment, whilst LRH-1 knockdown reduced ERα recruitment to ERα binding sites. Taken together, our findings establish a key role for LRH-1 in the regulation of ERα target genes in breast cancer cells and identify a mechanism in which co-operative binding of LRH-1 and ERα at estrogen response elements controls the expression of estrogen-responsive genes.
Project description:Unliganded Estrogen receptor alpha (ERa) has been implicated in ligand-dependent gene regulation. Upon ligand exposure, ERa binds to several EREs relatively proximal to the pre-marked, or persistent, ERa-bound sites and affects transient but robust gene expression. However, the underlying mechanisms are not fully understood. Here we demonstrate that upon ligand stimulation, persistent sites interact extensively, via chromatin looping, with the proximal transiently ERa-bound sites, forming Ligand Dependent ERa Enhancer Cluster in 3D (LDEC). The E2-target genes are regulated by these clustered enhancers but not by the H3K27Ac super-enhancers. Further, CRISPR-based deletion of TFF1 persistent site disrupts the formation of its LDEC resulting in the loss of E2-dependent expression of TFF1 and its neighboring genes within the same TAD. The LDEC overlap with nuclear ERa condensates that coalesce in a ligand and persistent site dependent manner. Furthermore, formation of clustered enhancers, as well as condensates, coincide with the active phase of signaling and their later disappearance results in the loss of gene expression even though persistent sites remain bound by ERa. Our results establish a direct link between ERa condensates, ERa enhancer clusters, and transient, but robust, gene expression in a ligand-dependent fashion.
Project description:Respiratory bursts were observed in A. bisporus. CO2 production and O2 consumption increased up to 3.5 fold during these 3 h bursts while compost temperature increased up to 3 °C. We set out to find which pathways were characteristic for these bursts and the interval between these bursts.
Project description:TFF1 overexpression in retinoblastoma cell line Y79 Differentially expressed genes and pathways involved in cancer progression were identified after TFF1 overexpression in Y79 cells by gene expression array analysis, underlining the effects on reduced tumorigenicity.