Profiling of Pol II occupancy in quiescent neural stem cells in Drosophila melanogaster
Ontology highlight
ABSTRACT:
ORGANISM(S): Drosophila melanogaster
PROVIDER: GSE81745 | GEO | 2018/04/06
REPOSITORIES: GEO
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Project description:In mammalian cells, widespread acceleration of cytoplasmic mRNA degradation is linked to impaired RNA polymerase II (Pol II) transcription. This mRNA decay-induced transcriptional repression occurs during infection with gammaherpesviruses including Kaposi’s sarcoma associated herpesvirus (KSHV) and murine gammaherpesvirus 68 (MHV68), which encode an mRNA endonuclease that initiates widespread RNA decay. Here, we show that MHV68-induced mRNA decay leads to a genome-wide reduction of Pol II occupancy at mammalian promoters. Viral genes, despite the fact that they require Pol II for transcription, escape this transcriptional repression. Protection is not governed by viral promoter sequences; instead, location on the viral genome is both necessary and sufficient to escape the transcriptional repression effects of mRNA decay. We hypothesize that the ability to escape from transcriptional repression is linked to the localization of viral DNA in replication compartments, providing a means for these viruses to counteract decay-induced viral transcript loss.
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Project description:Cell-type specific transcriptional profiling is key to understanding cell fate specification and function. In order to achieve this it has been necessary, to date, to isolate specific cell types from complex tissues. We have developed 'TaDa', a technique that enables cell-specific profiling without cell isolation. TaDa permits genome-wide profiling of DNA- or chromatin-binding proteins without cell sorting, fixation or affinity purification. The method is simple, sensitive, highly reproducible and is in principle transferable to any model system. Here we show that TaDa can be used to identify transcribed genes in a cell-type specific manner. We profile the genome-wide binding of RNA polymerase II (Pol II) in adjacent, clonally related neural stem cells in intact Drosophila brains. Our data reveal the activity of non-canonical metabolic pathways in proliferating neuroepithelial cells, and highlight a possible role for the retinal determination gene regulatory network in patterning neural stem cell fates. We also identify temporal differences in the activity of signalling pathways that control neuroepithelial cell fate by profiling Pol II occupancy at two different stages of brain development. Using RNA Pol II TaDa to profile, in a cell-type specific manner, the transcriptional state of neuroepithelial cells at two stages of larval brain development. Closely related asymmetrically dividing neural stem cells (neuroblasts) were also profiled, in order to compare the transcriptomes of two different types of neural stem cells. 3 biological relicates were performed for 3rd instar neuroepithelial cells (with one dye-swap). 2 biological relicates were performed for 3rd instar neuroblasts (with dye-swap). 2 biological relicates were performed for 1st instar neuroepithelial cells (with dye-swap). As additional supporting evidence for the Pol II TaDa technique, 2 biological relicates were performed for 3rd instar salivary glands (with dye-swap) in order to compare with previous Pol II-ChIP data for this tissue [PMID 22821985].
2013-06-21 | E-GEOD-46803 | biostudies-arrayexpress
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Project description:Control of RNA transcription is critical for the development and homeostasis of all organisms, and can occur at multiple steps of the transcription cycle, including RNA polymerase II (Pol II) recruitment, initiation, promoter-proximal pausing, and elongation. That Pol II accumulates on many promoters in metazoans implies that steps other than Pol II recruitment are rate-limiting and regulated 1-6. By integrating genome-wide Pol II chromatin immunoprecipition (ChIP) and Global Run-On (GRO) genomic data sets from Drosophila cells, we examined critical features of Pol II near promoters. The accumulation of promoter-proximal polymerase is widespread, occurring on 70% of active genes; and unlike elongating Pol II within the body of genes, promoter Pol II are held paused by factors like NELF, unable to transcribe unless nuclei are treated with strong detergent. Notably, we find that the vast majority of promoter-proximal Pol II detected by ChIP are paused, thereby identifying the biochemical nature of this rate-limiting step in transcription. Finally, we demonstrate that Drosophila promoters do not have the upstream divergent Pol II that is seen so broadly and prominently on mammalian promoters. We postulate this is a consequence of Drosophila’s extensive use of directional core promoter sequence elements, which contrasts with mammals’ lack of directional elements and prevalence of CpG island core promoters. In support of this idea, we show that the fraction of mammalian promoters containing a TATA box core element is dramatically depleted of upstream divergent transcription.
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Project description:Cell-type specific transcriptional profiling is key to understanding cell fate specification and function. In order to achieve this it has been necessary, to date, to isolate specific cell types from complex tissues. We have developed 'TaDa', a technique that enables cell-specific profiling without cell isolation. TaDa permits genome-wide profiling of DNA- or chromatin-binding proteins without cell sorting, fixation or affinity purification. The method is simple, sensitive, highly reproducible and is in principle transferable to any model system. Here we show that TaDa can be used to identify transcribed genes in a cell-type specific manner. We profile the genome-wide binding of RNA polymerase II (Pol II) in adjacent, clonally related neural stem cells in intact Drosophila brains. Our data reveal the activity of non-canonical metabolic pathways in proliferating neuroepithelial cells, and highlight a possible role for the retinal determination gene regulatory network in patterning neural stem cell fates. We also identify temporal differences in the activity of signalling pathways that control neuroepithelial cell fate by profiling Pol II occupancy at two different stages of brain development. Using RNA Pol II TaDa to profile, in a cell-type specific manner, the transcriptional state of neuroepithelial cells at two stages of larval brain development. Closely related asymmetrically dividing neural stem cells (neuroblasts) were also profiled, in order to compare the transcriptomes of two different types of neural stem cells.
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