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Essential Signaling Function of Cytoplasmic NELFB Independent of RNA Polymerase II Pausing

ABSTRACT: Biochemical studies have established that the four-subunit negative elongation factor (NELF) complex mediates RNA polymerase II (Pol II) pausing at promoter proximal regions. Genetic ablation of individual NELF subunits destabilizes the entire NELF complex and causes lethality of cultured cells, leading to the prevailing concept that NELF-mediated Pol II pausing is essential for cell survival. Using separation-of-function mutations, we show here that NELFB’s effects on cell proliferation can be uncoupled from its function in Pol II pausing. NELFB mutants localized in the cytoplasm and incapacitated in the NELF complex assembly still retain their ability to support cell proliferation and at least part of NELFB-dependent transcriptome. Furthermore, we demonstrate that cytoplasmic NELFB physically and functionally interacts with multiple pro-survival signaling kinases, most notably PI3K/AKT. Enforced activation of PI3K/AKT-related kinases largely rescues deficiency of NELFB-depleted cells in proliferation, but not Pol II pausing. Together, these data revise the current understanding of the growth impact of Pol II pausing and underscore multiplicity of the biological function of individual NELF subunits.

ORGANISM(S): Mus musculus

PROVIDER: GSE205388 | GEO | 2023/06/30

REPOSITORIES: GEO

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Essential Signaling Function of Cytoplasmic NELFB Independent of RNA Polymerase II Pausing [ChIP-seq]

Project description:Biochemical studies have established that the four-subunit negative elongation factor (NELF) complex mediates RNA polymerase II (Pol II) pausing at promoter proximal regions. Genetic ablation of individual NELF subunits destabilizes the entire NELF complex and causes lethality of cultured cells, leading to the prevailing concept that NELF-mediated Pol II pausing is essential for cell survival. Using separation-of-function mutations, we show here that NELFB’s effects on cell proliferation can be uncoupled from its function in Pol II pausing. NELFB mutants localized in the cytoplasm and incapacitated in the NELF complex assembly still retain their ability to support cell proliferation and at least part of NELFB-dependent transcriptome. Furthermore, we demonstrate that cytoplasmic NELFB physically and functionally interacts with multiple pro-survival signaling kinases, most notably PI3K/AKT. Enforced activation of PI3K/AKT-related kinases largely rescues deficiency of NELFB-depleted cells in proliferation, but not Pol II pausing. Together, these data revise the current understanding of the growth impact of Pol II pausing and underscore multiplicity of the biological function of individual NELF subunits.

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BRCA1 Balances the Action of a Transcription Elongation Factor In Mammary Gland Development and Tumorigenesis (sequencing)

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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.

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