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Local inhibition of protein phosphatase 1 by NUAK1 promotes spliceosome assembly and reveals a MYC-sensitive feedback control of transcriptional elongation

ABSTRACT: Deregulated expression of MYC induces a dependence on the NUAK1 kinase, but the molecular mechanisms underlying this dependence have not been fully clarified. Here we show that NUAK1 is a predominantly nuclear protein that associates with a network of nuclear protein phosphatase 1 (PP1) interactors and that PNUTS, a nuclear regulatory subunit of PP1, is phosphorylated by NUAK1. Both NUAK1 and PNUTS associate with the splicing machinery. Inhibition of NUAK1 abolishes chromatin association of PNUTS, reduces spliceosome activity and suppresses nascent RNA synthesis. Activation of MYC does not bypass the requirement for NUAK1 for spliceosome activity, but significantly attenuates transcription inhibition. Consequently, NUAK1 inhibition in MYC-transformed cells induces global accumulation of RNAPII both at the pause-site and at the first exon/intron boundary, but does not increase mRNA synthesis. We suggest that NUAK1 inhibition in the presence of deregulated MYC traps non-productive RNAPII due to the absence of correctly assembled spliceosomes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE129925 | GEO | 2020/02/01

REPOSITORIES: GEO

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Colorectal tumors require NUAK1 for protection from oxidative stress

Project description:NUAK1 is a member of the AMPK family of kinases involved in regulation of cell adhesion, metabolism and stress responses. Our previous analysis revealed a requirement for NUAK1 to sustain viability when MYC is overexpressed. Human colorectal cancer (CRC) shows near uniform overexpression of MYC, suggesting that this cancer may be particularly amenable to NUAK1 inhibition. This work reveals that elevated NUAK1 expression in human CRC correlates with more aggressive disease, lymph node metastasis and reduced overall survival. Deletion of Nuak1 in murine intestines prevented outgrowth of colonic tumors driven by loss of Apc and KRas mutation, while depletion of Nuak1 in pre-existing tumors drove rapid tumor regression. Mechanistically, we show that NUAK1 promotes anti-oxidant gene expression by facilitating nuclear import of NRF2. Deletion or inhibition of NUAK1 renders cells vulnerable to oxidative stress and provision of exogenous anti-oxidants protects cells in culture and colonic tumors in situ from Nuak1 depletion.

2018-02-26 | PXD008229 | Pride

Control of RNA pol II speed by PNUTS-PP1 and Spt5 dephosphorylation facilitates termination by a “sitting duck torpedo” mechanism

Project description:Control of transcription speed, which influences many co-transcriptional processes, is poorly understood. We report that PNUTS-PP1 phosphatase is a negative regulator of RNA pol II elongation rate. The PNUTS W401A mutation, which disrupts PP1 binding, causes genome-wide acceleration of transcription associated with hyper-phosphorylation of the Spt5 elongation factor. Immediately downstream of poly(A) sites, pol II decelerates from >2kb/min to <1 kb/min, which correlates with Spt5 dephosphorylation. Pol II deceleration and Spt5 dephosphorylation require poly(A) site recognition and the PNUTS-PP1 complex, which is in turn necessary for transcription termination. These results lead to a new model for termination, the “sitting duck torpedo” mechanism, where poly(A) site-dependent deceleration caused by PNUTS-PP1 and Spt5 dephosphorylation is required to convert pol II into a viable target for the Xrn2 terminator exonuclease. Spt5 and its bacterial homologue NusG therefore have related functions controlling kinetic competition between RNA polymerases and the termination factors that pursue them.

2019-10-30 | GSE134198 | GEO

Ubiquitin-dependent transfer of PAF1c from MYC onto RNA Polymerase controls double-strand break repair at active promoters

Project description:MYC family proteins are oncogenic transcription factors that can globally affect the function of RNA Polymerase II (RNAPII). The ability of MYC proteins to promote transcription elongation depends on their ubiquitination, but the underlying mechanism and its biological relevance are unknown. Here we show that MYC and the Polymerase II associated factor, PAF1c, interact directly and their function is mutually dependent, since the specific binding of MYC to active promoters depends on PAF1c and, conversely, PAF1c is required for MYC-dependent pause release. Upon binding, PAF1c is rapidly transferred from MYC onto RNAPII and this transfer is driven by the HUWE1 ubiquitin ligase. Both MYC and HUWE1 globally control histone H2B ubiquitylation, which promotes transcriptional elongation and alters chromatin structure for double-strand break repair. Consistently, MYC suppresses the accumulation of double-strand breaks at promoters in response to topoisomerase II inhibition. While depletion of PAF1c has only minor effects on MYC-dependent gene expression, MYC induces rampant transcription-dependent DNA damage in PAF1c-depleted cells. We propose that the HUWE1-dependent transfer of PAF1c from MYC onto RNAPII is critical for absorbing the topological stress accompanied with deregulated and oncogenic transcription.

2021-02-15 | PXD023242 | Pride

Aging-regulated PNUTS maintains endothelial barrier function via SEMA3B suppression [PNUTS]

Project description:Age-related diseases pose great challenges to health care systems worldwide. During aging, endothelial senescence increases the risk for cardiovascular disease. Recently, it was described that Phosphatase 1 Nuclear Targeting Subunit (PNUTS) has a central role in cardiomyocyte aging and homeostasis. Here, we determined the role of PNUTS in endothelial cell aging. We confirmed that PNUTS is repressed in senescent endothelial cells (ECs). Moreover, PNUTS silencing elicits several of the hallmarks of endothelial aging: senescence, reduced angiogenesis and loss of barrier function. To validate our findings in vivo, we generated an endothelial-specific inducible PNUTS-deficient mouse line (Cdh5-CreERT2;PNUTSfl/fl), termed PNUTSEC-KO. Two weeks after PNUTS deletion, PNUTSEC-KO mice presented severe multiorgan failure and vascular leakage. Transcriptomic analysis of PNUTS-silenced HUVECs and lungs of PNUTSEC-KO mice revealed that the PNUTS-PP1 axis tightly regulates the expression of semaphorin 3B (SEMA3B). Indeed, silencing of SEMA3B completely restored barrier function after PNUTS loss-of-function. These results reveal a pivotal role for PNUTS in endothelial homeostasis through a SEMA3B downstream pathway that provides a potential target against the effects of aging in ECs.

2024-04-15 | GSE263742 | GEO

Aging-regulated PNUTS maintains endothelial barrier function via SEMA3B suppression

2024-04-14 | GSE263531 | GEO

The PNUTS-protein phosphatase 1 complex acts as an intrinsic barrier to KSHV replication [eCLIP]

Project description:Control of RNA Polymerase II (pol II) elongation is a critical component of gene expression in mammalian cells. The PNUTS-protein phosphatase 1 (PP1) complex controls elongation rates, slowing pol II after polyadenylation sites to promote termination. The Kaposi's sarcoma-associated herpesvirus (KSHV) co-opts pol II to express its genes, but little is known about its regulation of pol II elongation. We identified PNUTS as a suppressor of a KSHV reporter gene in a genome-wide CRISPR screen. PNUTS depletion also enhances global KSHV gene expression and overall viral replication. Reflecting its host gene activities, PNUTS binds viral RNAs downstream of polyadenylation sites, restricts transcription readthrough of viral genes, and requires PP1 interaction. Surprisingly, PNUTS represses the KSHV reporter by decreasing productive elongation at the 5´-end of the gene. From these data, we conclude that PNUTS' activity forms an intrinsic barrier to KSHV replication likely by suppressing pol II elongation at promoter-proximal regions.

2022-11-19 | GSE201045 | GEO

The PNUTS-protein phosphatase 1 complex acts as an intrinsic barrier to KSHV replication [CRISPR]

2022-11-19 | GSE200991 | GEO

The PNUTS-protein phosphatase 1 complex acts as an intrinsic barrier to KSHV replication [ChIP-seq]

2022-11-19 | GSE200992 | GEO

The PNUTS-protein phosphatase 1 complex acts as an intrinsic barrier to KSHV replication [RNA-seq]

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The 3’-UTR of MYC couples RNA polymerase II function to ribonucleotide levels

Project description:Deregulated expression of MYC enhances glutamine utilization and renders cell survival dependent on glutamine, inducing “glutamine addiction”. Surprisingly, colon cancer cells that express high levels of MYC due to WNT pathway mutations, are not glutamine-addicted but undergo a reversible cell cycle arrest upon glutamine deprivation. We show here that glutamine deprivation suppresses translation of endogenous MYC via the 3’-UTR of the MYC mRNA, enabling escape from apoptosis. This regulation is mediated by glutamine-dependent changes in adenosine nucleotide levels. Glutamine deprivation causes a global reduction in promoter association of RNA Polymerase II (RNAPII) and slows transcriptional elongation. While activation of MYC restores binding of MYC and RNAPII function on most promoters, restoration of elongation is imperfect and activation of MYC in the absence of glutamine causes stalling of RNAPII on multiple genes, correlating with R-loop formation. Stalling of RNAPII and R-loop formation can cause DNA damage, arguing that the MYC 3’-UTR is critical for maintaining genome stability when ribonucleotide levels are low.

2022-02-28 | PXD005829 | Pride

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