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Genome-wide uniformity of human “open” pre-initiation complexes

ABSTRACT: Transcription of protein-coding and noncoding DNA occurs pervasively throughout the mammalian genome. Their sites of initiation are generally inferred from transcript 5’ ends, and are thought to be either locally dispersed or focused. How these two modes of initiation relate is unclear. Here, we apply permanganate treatment and chromatin immunoprecipitation (PIP-seq) of initiation factors to identify the precise location of melted DNA separately associated with the pre-initiation complex (PIC) and the adjacent paused complex (PC). This approach revealed the two known modes of transcription initiation. However, in contrast to prevailing views they co-occurred within the same promoter region: initiation originating from a focused PIC, and broad nucleosome-linked initiation. PIP-seq allowed transcriptional orientation of Pol II to be determined, which may be useful near promoters where sufficient sense/anti-sense transcript mapping information is lacking. PIP-seq detected divergently oriented Pol II at both coding and noncoding promoters, as well as at enhancers. Their occupancy levels were not necessarily coupled in the two orientations. DNA sequence and shape analysis of initiation complex sites suggest that both sequence and shape contribute to specificity, but in a context-restricted manner. That is, initiation sites have the locally “best” initiator (INR) sequence and/or shape. These finding reveal a common core to pervasive Pol II initiation throughout the human genome.

ORGANISM(S): Homo sapiens

PROVIDER: GSE76955 | GEO | 2016/10/19

SECONDARY ACCESSION(S): PRJNA309133

REPOSITORIES: GEO

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RPAP2 regulates a transcription initiation checkpoint by prohibiting assembly of preinitiation complex [ChIP-seq]

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RPAP2 regulates a transcription initiation checkpoint by prohibiting assembly of preinitiation complex [ChIP-Rx]

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Structural basis of SNAPc-dependent snRNA transcription intiation by RNA polymerase II

Project description:RNA Polymerase II (Pol II) carries out transcription of both protein-coding and non-coding genes. Whereas Pol II initiation at protein-coding genes has been studied in detail, Pol II initiation at non-coding genes such as small nuclear RNA (snRNA) genes is not understood at the structural level. Here we study Pol II initiation at snRNA gene promoters and show that the snRNA-activating protein complex (SNAPc) enables DNA opening and transcription initiation independent of TFIIE and TFIIH in vitro. We then resolve cryo-EM structures of the SNAPc-containing Pol II preinitiation complex (PIC) assembled on U1 and U5 snRNA promoters. The core of SNAPc binds two turns of DNA and recognizes the snRNA promoter-specific proximal sequence element (PSE) located upstream of the TATA box-binding protein TBP. Two extensions of SNAPc called wing-1 and wing-2 bind TFIIA and TFIIB, respectively, explaining how SNAPc directs Pol II to snRNA promoters. Comparison of structures of closed and open promoter complexes elucidates TFIIH-independent DNA opening. These results provide the structural basis of Pol II initiation at non-coding RNA gene promoters.

2023-03-11 | PXD033638 | Pride

TFIID enables RNA polymerase II promoter-proximal pausing

Project description:RNA polymerase II (pol II) transcribes all protein-coding and many non-coding RNAs in the human genome. Pol II transcription initiation is governed by the Pre-Initiation Complex (PIC), which contains TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH, pol II, and Mediator. After initiation, pol II enzymes typically pause after transcribing less than 100 bases, and paused polymerases represent a common regulatory intermediate. Accordingly, paused pol II has been implicated in enhancer function, development and homeostasis, and diseases ranging from cancer to viral pathogenesis. Precisely how pol II promoter-proximal pausing is enforced and regulated remains unclear; however, protein complexes such as NELF and DSIF increase pausing whereas the activity of CDK9 (P-TEFb complex) correlates with pause release. To address specific mechanistic questions about pol II pausing and its regulation, we reconstituted human pol II promoter-proximal pausing in vitro, entirely with purified factors (no extracts). As expected, NELF and DSIF increased pol II pausing in vitro, whereas P-TEFb promoted pause release. Unexpectedly, the PIC alone was sufficient to reconstitute pol II pausing, suggesting that pausing is an inherent property of the PIC. In agreement, pol II pausing was lost upon replacement of the TFIID complex with TATA-binding protein (TBP); moreover, pausing was dependent upon TFIID subunits TAF1 and TAF2. TAF1/2 bind genomic DNA downstream of the pol II initiation site, invoking a “complex interaction” model for pausing. Consistent with this model, PRO-Seq experiments revealed increased transcription upon acute depletion (t=60 min) of TAF1 and TAF2 in human cells, and pol II pausing was disrupted at thousands of genes. Similar results were obtained in TAF1-depleted Drosophila S2 cells. Collectively, these data establish the general transcription factor TFIID as a genome-wide regulator of pol II promoter-proximal pausing.

2020-05-28 | GSE132764 | GEO

Requirements for preinitiation complex formation in vivo

Project description:Transcription by RNA polymerase (Pol) II requires assembly of a preinitiation complex (PIC) composed of general transcription factors (GTFs) bound at the core promoter. In vitro, the TATA-binding protein (TBP), TFIIB, TFIIF, and Pol II are essential for PIC formation and transcriptional initiation, whereas TFIIA, TFIIE, and TFIIH are not required under certain conditions. In addition, the PIC is stable in the absence of nucleotide triphosphates, and sequential addition of GTFs results in a series of partial PICs. Here, we analyze the roles of all GTFs in yeast cells by measuring PIC formation and Pol II transcription upon depletion of individual GTFs. All GTFs are essential for TBP binding and Pol II transcription in vivo, suggesting that partial PICs composed of GTF subsets do not exist at appreciable levels. In contrast, TBP-associated factors (TAFs) contribute to Pol II transcriptional activity at most (and perhaps all) genes, but TAF-independent transcription occurs at a substantial level, particularly at promoters lacking canonical TATA elements. Lastly, unlike the case in vitro, PICs are not observed in cells deprived of uracil, and presumably UTP, suggesting a mechanism that removes transcriptionally inactive PICs from promoters.

2019-02-27 | GSE122734 | GEO

Stably-paused genes revealed through inhibition of transcription initiation by the TFIIH inhibitor Triptolide

Project description:Transcription by RNA Polymerase II (Pol II) in metazoan is regulated in several steps, including preinitiation complex (PIC) formation, initiation, Pol II escape, productive elongation, cotranscriptional RNA-processing and termination. Genome-wide studies have demonstrated that the phenomenon of promoter-bound Pol II pausing is widespread, especially for genes involved in developmental and stimulus-responsive pathways. However, a mechanistic understanding of the paused Pol II states at promoters is limited. For example, at a global level, it’s unclear to what extent the engaged paused Pol II is stably tethered to the promoter or undergoes rapid cycles of initiation and termination. Here we used the small molecule Triptolide (TPL), an XPB/TFIIH inhibitor, to block transcriptional initiation followed by measuring Pol II occupancy by ChIP-seq. This inhibition of initiation enables us to investigate different states of paused Pol II. Specifically, our global analysis reveals that most genes with paused Pol II, as defined by pausing index, show significant clearance of Pol II during the period of TPL treatment. Our study further identifies a group of genes with unexpectedly stably-paused Pol II, with unchanged Pol II occupancy even after one hour of inhibition of initiation. This group of genes constitutes a small portion of all paused genes defined by the conventional criterion of pausing index. These findings could pave the way for evaluating the contribution of different elongation/pausing factors on different states of Pol II pausing in developmental and other stimulus-responsive pathways. ChIP-Seq of total/Ser5P Pol II in HCT116 cells treated with DMSO or TPL in serum starvation/activation or normal conditions. Nascent RNA-seq in HCT116 cells treated with DMSO or TPL in starved condition.

2015-01-05 | E-GEOD-63314 | biostudies-arrayexpress

Stably-paused genes revealed through inhibition of transcription initiation by the TFIIH inhibitor Triptolide

2015-01-05 | GSE63314 | GEO

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2023-03-11 | PXD029840 | Pride

Crosslinking mass spectrometry of yeast Pol I pre-initiation complex

Project description:In eukaryotic cells, ribosomal RNA is transcribed by RNA polymerase I (Pol I). To initiate transcription, Pol I requires the assembly of a multi-subunit pre-initiation complex (PIC). In yeast, the minimal PIC includes Pol I, the transcription factor Rrn3 and Core Factor (CF) composed of subunits Rrn6, Rrn7 and Rrn11. We have determined the cryo-EM structure of a 18-subunit yeast Pol I complex together with CF, Rrn3 and transcription scaffold. To aid in modeling the structure based on the cryo-EM map, we performed crosslinking mass spectrometry.

2017-07-31 | PXD006510 | Pride

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