Identification of sequence-specific promoters driving polycistronic transcription initiation by RNA Polymerase II in trypanosomes
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PROVIDER: PRJNA541456 | ENA |
REPOSITORIES: ENA
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Project description:Protein coding genes in the trypanosome genome are organized in polycistronic transcription units (PTUs). How RNA Polymerase II (Pol II) initiates PTU transcription has not been resolved and the current model favors initiation driven by chromatin epigenetic marks, rather than core-promoters. Here, we identify sequence-specific core promoters by functional characterization of ChIP-Seq Pol II accumulation-peaks. Sequences located between oppositely orientated PTUs contained two independent and distinct core promoters, driving unidirectional transcription. Detailed analysis of one promoter identified 75 bp, necessary and sufficient to fully drive reporter expression, and containing short functional motifs. Analysis of further promoters suggested activity and initiation is regulated and both, focused and dispersed transcription patterns were found. Thus, in contrast to the model of unregulated and promoter-independent transcription initiation, sequence-specific promoters determine the initiation of RNA Pol II transcription of protein coding genes in trypanosomes. These findings resolve the discrepancy between trypanosomes and other eukaryotes in how Pol II initiates protein-coding gene transcription.
2021-02-01 | GSE130798 | GEO
Project description:Genome-wide transcription studies are revealing increasing examples of ‘dispersed promoters’ that unlike ‘focused promoters’, lack well-conserved sequence motifs and tight regulation. Dispersed promoters are nevertheless marked by well-defined chromatin structures, suggesting that specific sequence elements must exist in these unregulated promoters. Here, we have analyzed regions of transcription initiation in the eukaryotic parasite Trypanosoma brucei, in which RNA polymerase II transcription initiation and occurs over broad regions without distinct promoter motifs and lacks regulation. Using a combination of site-specific and genome-wide assays, we identified GT-rich promoters that can drive unidirectional transcription and promote the targeted deposition of the histone variant H2A.Z in a genomic context dependent manner. In addition, upon mapping nucleosome occupancy at high resolution, we find nucleosome positioning to correlate with RNA pol II enrichment and gene expression, pointing to a role in RNA maturation. Nucleosome positioning may thus represent a previously unrecognized layer of gene regulation in trypanosomes. Our findings show that even highly dispersed, unregulated promoters contain specific DNA elements that are able to induce transcription and changes in chromatin structure.
2017-05-31 | GSE98061 | GEO
Project description:Transcription regulation occurs frequently through promoter-associated pausing of RNA polymerase II (Pol II). We developed a Precision nuclear Run-On and sequencing assay (PRO-seq) to map the genome-wide distribution of transcriptionally-engaged Pol II at base-pair resolution. Pol II accumulates immediately downstream of promoters, at intron-exon junctions that are efficiently used for splicing, and over 3' poly-adenylation sites. Focused analyses of promoters reveal that pausing is not fixed relative to initiation sites nor is it specified directly by the position of a particular core promoter element or the first nucleosome. Core promoter elements function beyond initiation, and when optimally positioned they act collectively to dictate the position and strength of pausing . We test this ‘Complex Interaction’ model with insertional mutagenesis of the Drosophila Hsp70 core promoter. Identification of RNA polymerase active sites in Drosophila S2 cell line using PRO-seq method. Identification of transcription initiation sites in Drosophila S2 cell line using PRO-cap method. Identification of changes in RNA polymerase active sites on transgenic Hsp70 promoters upon disruption of DNA sequence elements in 3 transgenic fly lines using PRO-seq method.
2013-02-01 | E-GEOD-42117 | biostudies-arrayexpress
Project description:Transcription regulation occurs frequently through promoter-associated pausing of RNA polymerase II (Pol II). We developed a Precision nuclear Run-On and sequencing assay (PRO-seq) to map the genome-wide distribution of transcriptionally-engaged Pol II at base-pair resolution. Pol II accumulates immediately downstream of promoters, at intron-exon junctions that are efficiently used for splicing, and over 3' poly-adenylation sites. Focused analyses of promoters reveal that pausing is not fixed relative to initiation sites nor is it specified directly by the position of a particular core promoter element or the first nucleosome. Core promoter elements function beyond initiation, and when optimally positioned they act collectively to dictate the position and strength of pausing . We test this ‘Complex Interaction’ model with insertional mutagenesis of the Drosophila Hsp70 core promoter.
2013-02-01 | GSE42117 | GEO
Project description:CTCF blocks anti-sense transcription initiation at divergent gene promoters
| PRJNA725532 | ENA
Project description:The nuclear envelope serves as important mRNA surveillance system. In yeast and human, several control systems act in parallel to prevent nuclear export of unprocessed mRNAs. Trypanosomes lack homologues to most of the involved proteins and their nuclear mRNA metabolism is non-conventional exemplified by polycistronic transcription and mRNA processing by trans-splicing. We here visualised nuclear export in trypanosomes by probing large, endogenous mRNA by intramolecular multi-colour single molecule FISH (smFISH). In addition, unspliced mRNAs were visualised by co-probing two adjacent introns or intergenic regions. We found that the initation of nuclear export requires neither the completion of transcription nor trans-splicing. Nevertheless, the inhibition of trans-splicing blocked cytoplasmic transport of the of unspliced mRNAs and only a small fraction reached the nucleus-distant cytoplasm. Most of the unspliced transcripts remained at the nuclear periphery, within transport and in nuclear periphery granules (NPGs) localised at the cytoplasmic site of nuclear pores that resemble stress granules in composition. Our work shows that, in striking contrast to other eukaryotes, trypanosomes can start nuclear export while the mRNA is still transcribed, but unspliced transcripts remain ‘stuck’ in nuclear pores, probably awaiting processing or decay. Our data indicate that trypanosomes regulate the completion of nuclear export rather than the start.
2018-10-26 | PXD010143 | Pride
Project description:Herpesvirus late promoters activate gene expression after viral DNA synthesis has begun. Alphaherpesviruses utilize a viral immediate-early protein to do this, whereas beta- and gammaherpesviruses primarily use a 6-member set of viral late-acting transcription factors (LTF) that are drawn to a TATT sequence in the late promoter. The betaherpesvirus, human cytomegalovirus (HCMV), produces three immediate-early 2 protein isoforms, IE2-86, IE2-60, IE2-40, in late infection, but whether they activate late viral promoters is unknown. Here, we quickly degrade the IE2 proteins in late infection and analyze effects on transcription using customized PRO-Seq and computational methods combined with multiple validation methods. We discover that the IE2 proteins selectively drive RNA Pol II transcription initiation at a subset of viral early-late and late promoters common to different HCMV strains, but do not substantially affect Pol II transcription of the 9,942 expressed host genes. Most of the IE2-activated viral late infection promoters lack the TATT sequence bound by the HCMV UL87-encoded LTF. The HCMV TATT-binding protein is not mechanistically involved in late RNA expression from the IE2-activated TATT-less UL83 (pp65) promoter, as it is for the TATT-containing UL82 (pp71) promoter. While antecedent viral DNA synthesis is necessary for transcription from the late infection viral promoters, continued viral DNA synthesis is unnecessary. We conclude that the IE2 proteins target a distinct subset of late infection HCMV promoters for transcription initiation by RNA Pol II. Commencement of viral DNA replication renders the HCMV genome late promoters susceptible to late-acting viral transcription factors, which do not appreciably affect host transcription during this late time.
2020-03-05 | GSE139114 | GEO
Project description:RNA polymerase II (Pol II) pauses downstream of the transcription initiation site before beginning productive elongation. This pause is a key component of metazoan gene expression regulation. Some promoters have a strong disposition for Pol II pausing and often mediate faster, more synchronous changes in expression. This requires multiple rounds of transcription and thus cannot rely solely on pause release. But it is unclear how pausing affects the initiation of new transcripts during consecutive rounds of transcription. Using our recently developed ChIP-nexus method, we find that Pol II pausing inhibits new initiation. We propose that paused Pol II helps prevent new initiation between transcription bursts, which may reduce noise.
2017-04-17 | GSE85741 | GEO
Project description:We describe the results of a genome-wide analysis of human cells that suggests most protein coding genes, including most genes thought to be transcriptionally inactive, experience transcription initiation. We found that nucleosomes with H3K4me3 and H3K9/14Ac modifications, together with RNA polymerase II, occupy the promoters of most protein coding genes in human embryonic stem cells. Only a subset of these genes produce detectable full length transcripts and are occupied by nucleosomes with H3K36me3 modifications, a hallmark of elongation. The other genes experience transcription initiation but show no evidence of elongation, suggesting that they are predominantly regulated at post-initiation steps. Genes encoding most developmental regulators fall into this group. Our results also identify a class of genes that are excluded from experiencing transcriptional initiation, where mechanisms that prevent initiation must predominate. These observations extend to differentiated cells, suggesting that transcription initiation at most genes is a general phenomenon in human cells.
2008-06-27 | E-TABM-277 | biostudies-arrayexpress
Project description:Mammalian transcriptomes are complex and formed by extensive promoter activity. Moreover, gene promoters are largely divergent and initiate transcription of reverse-oriented promoter upstream transcripts (PROMPTs). Although PROMPTs are commonly terminated early, influenced by early polyadenylation (pA) sites, promoters often cluster so that the divergent activity of one might impact another. Here, we find that the distance between promoters strongly correlates with the expression, stability and length of their associated PROMPTs. Adjacent promoters driving divergent mRNA transcription support PROMPT formation, but due to pA site constraints, these transcripts tend to spread into the neighboring mRNA on the same strand. This mechanism to derive new alternative mRNA transcription start sites (TSSs) is also evident at closely spaced promoters supporting convergent mRNA transcription. We suggest that basic building blocks of divergently transcribed core promoter pairs, in combination with the wealth of TSSs in mammalian genomes, provides a framework with which evolution shapes transcriptomes. Mapping of paired 5â?? and 3â??ends of capped and polyadenylated RNAs from RRP40-depleted and eGFP control HeLa cells and using transcript isoform sequencing (TIF-Seq, see Pelechano et al. Nat Protoc 2014 (PMID: 24967623) and Pelechano et al. Nature 2013 (PMID: 23615609)).
2016-05-13 | E-GEOD-75183 | biostudies-arrayexpress