Project description:Glucocorticoids are widely prescribed anti-inflammatory drugs with tissue-specific effects. Beneficial anti-inflammatory effects are caused in cells of the immune system whereas metabolic adverse effects of glucocorticoid therapy are seen in metabolic tissues such as liver. The glucocorticoid receptor (GR), a nuclear receptor targeted by glucocorticoids, bind its DNA response elements upon ligand exposure in a tissue-specific manner. Tissue-specific GR binding patterns depend on the access of its binding sites, which determines the tissue-specific glucocorticoid response. Here, we investigated this response by nascent RNAseq in murine bone marrow-derived macrophages (BMDMs) after stimulation with lipopolysaccharide (LPS) and dexamethasone (Dex). After labelling newly synthesized transcripts with 4-thiouracile (4sU), we identified macrophage-specific non-coding transcripts expressed at intergenic GR binding sites. Those transcripts are regulated by the GR and correlate with its anti-inflammatory function in macrophages. Those findings add another layer to the mechanisms underpinning GR's tissue-specific gene regulation and represent potential drug targets in anti-inflammatory therapy and/or management of adverse effects in glucocorticoid therapy.
Project description:To identify transcriptionally regulated genes in primary mouse macrophages stimulated with LPS with high sensitivity, we isolated nascent RNA following metabolic labelling with 4-thiouridine during the last 35 min before cell harvest, as recently described (Dolken et al. 2008 RNA 14:1959-72). Microarray analyses of nascent RNA identified substantially more probe sets as up-regulated after 45 min of LPS stimulation than parallel analyses of total cellular RNA. In contrast, 4.5 h after stimulation, up-regulated genes in total and nascent RNA largely overlapped. This approach therefore allowed a much more sensitive detection of early changes in transcription, and the respective genes are likely to be direct targets of LPS-regulated transcription factors. Keywords: Effect of LPS stimulation; comparison of changes in expression of total versus nascent RNA; timecourse Two completely independent experiments were performed. Macrophages were stimulated with 100 ng/ml LPS for 45 or 270 minutes. Thiouridine pulsing was done in last 35 minutes before harvest. Total RNA was isolated. Nascent RNA was subsequently purified.
Project description:To identify transcriptionally regulated genes in primary mouse macrophages stimulated with LPS with high sensitivity, we isolated nascent RNA following metabolic labelling with 4-thiouridine during the last 35 min before cell harvest, as recently described (Dolken et al. 2008 RNA 14:1959-72). Microarray analyses of nascent RNA identified substantially more probe sets as up-regulated after 45 min of LPS stimulation than parallel analyses of total cellular RNA. In contrast, 4.5 h after stimulation, up-regulated genes in total and nascent RNA largely overlapped. This approach therefore allowed a much more sensitive detection of early changes in transcription, and the respective genes are likely to be direct targets of LPS-regulated transcription factors. Keywords: Effect of LPS stimulation; comparison of changes in expression of total versus nascent RNA; timecourse
Project description:In the opportunistic pathogen Pseudomonas aeruginosa RsmA is an RNA-binding protein that plays critical roles in the control of virulence, interbacterial interactions and biofilm formation. Although RsmA is thought to exert its regulatory effects by binding full-length transcripts, the extent to which RsmA binds nascent transcripts has not been addressed. Moreover, which transcripts are direct targets of this key post-transcriptional regulator is largely unknown. Using chromatin immunoprecipitation coupled with high-throughput DNA sequencing, with cells grown in the presence and absence of the RNA polymerase inhibitor rifampicin, we identify hundreds of nascent transcripts that RsmA associates with in P. aeruginosa. We also find that the RNA chaperone Hfq targets a subset of the RsmA-associated nascent transcripts and that the two RNA-binding proteins can exert regulatory effects on common targets. Our findings establish that RsmA associates with many transcripts as they are being synthesized in P. aeruginosa, identify the direct targets of RsmA, and suggest that RsmA and Hfq may act in a combinatorial fashion on certain target transcripts. More broadly, our data suggest that the binding of post-transcriptional regulators to nascent transcripts may be commonplace in bacteria where distinct regulators can function alone or in concert to achieve control over the translation of transcripts as soon as they emerge from RNA polymerase.
Project description:In response to elevated glucocorticoid levels, erythroid progenitors rapidly expand to produce large numbers of young erythrocytes. Previous work demonstrates hematopoietic changes in rodents exposed to various physical and psychological stressors, however, the effects of chronic psychological stress on erythropoiesis has not be delineated. We employed laboratory, clinical and genomic analyses of a murine model of chronic restraint stress (RST) to examine the influence of psychological stress on erythropoiesis. Mice exposed to RST demonstrated markers of early erythroid expansion involving the glucocorticoid receptor. In addition, these RST-exposed mice had increased numbers of circulating reticulocytes and increased erythropoiesis in primary and secondary erythroid tissues. Mice also showed increases in erythroid progenitor populations and elevated expression of the erythroid transcription factor KLF1 in these cells. Together this work describes some of the first evidence of psychological stress affecting erythroid homeostasis through glucocorticoid stimulation and begins to define the transcription factor pathway involved.
Project description:Changes in gene transcription regulation are necessary for species to respond to changes in their environment. In particular, host-pathogen dynamics have been observed to entail rapid evolution of genes involved in the host innate immune system. Cytokines such as type I interferon alpha and beta trigger an antiviral cellular state controlled by members of the transcription factor families STAT and IRF. However, it remains poorly understood how gene transcription regulation has been rewired through evolutionary time to achieve species-specific interferon-controlled changes in gene expression. We generated nascent transcription (PRO-seq) datasets to determine the initial transcriptional response on lymphoblastoid cell lines derived from homo sapiens and macaca mulatta upon stimulation with interferon alpha2 to assess species-specific changes in gene regulation.
Project description:Transcription-factor binding to cis-regulatory regions regulates the gene expression program of a cell, but occupancy is often a poor predictor of the gene response. Here, we show that glucocorticoid stimulation led to the reorganization of transcriptional coregulators MED1 and BRD4 within topologically associating domains (TADs), resulting in active or repressive gene environments. Indeed, we observed a bias toward the activation or repression of a TAD when their activities were defined by the number of regions gaining and losing MED1 and BRD4 following dexamethasone (Dex) stimulation. Variations in Dex-responsive genes at the RNA levels were consistent with the redistribution of MED1 and BRD4 at the associated cis-regulatory regions. Interestingly, Dex-responsive genes without the differential recruitment of MED1 and BRD4 or binding by the glucocorticoid receptor were found within TADs, which gained or lost MED1 and BRD4, suggesting a role of the surrounding environment in gene regulation. However, the amplitude of the response of Dex-regulated genes was higher when the differential recruitment of the glucocorticoid receptor and transcriptional coregulators was observed, reaffirming the role of transcription factor-driven gene regulation and attributing a lesser role to the TAD environment. These results support a model where a signal-induced transcription factor induces a regionalized effect throughout the TAD, redefining the notion of direct and indirect effects of transcription factors on target genes.