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Inhibition of CBP synergizes with the RNA-dependent mechanisms of Azacitidine by limiting protein synthesis.

ABSTRACT: The nucleotide analogue azacitidine (AZA) is currently the best treatment option for patients with high-risk myelodysplastic syndromes (MDS). However, only half of treated patients respond and of these almost all eventually relapse. New treatment options are urgently needed to improve the clinical management of these patients. Here, we perform a loss-of-function shRNA screen and identify the histone acetyl transferase and transcriptional co-activator, CREB binding protein (CBP), as a major regulator of AZA sensitivity. Compounds inhibiting the activity of CBP and the closely related p300 synergistically reduce viability of MDS-derived AML cell lines when combined with AZA. Importantly, this effect is specific for the RNA-dependent functions of AZA and not observed with the related compound decitabine that is only incorporated into DNA. The identification of immediate target genes leads us to the unexpected finding that the effect of CBP/p300 inhibition is mediated by globally down regulating protein synthesis.

SUBMITTER: Diesch J

PROVIDER: S-EPMC8523560 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Inhibition of CBP synergizes with the RNA-dependent mechanisms of azacitidine by limiting protein synthesis

Project description:The nucleotide analogue azacitidine interferes with RNA and DNA metabolism and is currently the best treatment option for a subset of patients with high-risk myelodysplastic syndromes. However, only half of treated patients respond and almost all patients that initially respond eventually relapse. We performed an optimized loss-of-function shRNA screen in combination with azacitidine treatment in an MDS-derived acute myeloid leukemia cell line to identify chromatin regulators affecting drug response. We identified CBP, as a major regulator of azacitidine sensitivity. Compounds inhibiting the enzymatic activity of CBP synergistically reduced viability of MDS-derived AML cell lines when combined with AZA. Surprisingly, this effect was specific for the RNA-dependent functions of AZA and not observed with the related compound decitabine that is limited to DNA incorporation. The identification of immediate target genes suggested that the effect of CBP inhibition is mediated by downregulation of genes encoding the translational machinery, which could be confirmed in proteomic analysis of nascent proteins. Furthermore, proteins most affected by CBP inhibition include key drivers of cell cycle progression.

2021-09-10 | GSE158813 | GEO

Inhibition of CBP synergizes with the RNA-dependent mechanisms of azacitidine by limiting protein synthesis

2021-09-10 | GSE158738 | GEO

Inhibition of CBP synergizes with the RNA-dependent mechanisms of azacitidine by limiting protein translation

Project description:The nucleotide analogue azacitidine (AZA) interferes with RNA and DNA metabolism and is currently the best treatment option for a subset of patients with high-risk myelodysplastic syndromes. However, only half of treated patients respond and almost all patients that initially respond eventually relapse. Thus, response-predicting biomarkers and new treatment options are urgently needed to improve the clinical management of these patients. Here, we performed a loss-of-function shRNA screen in combination with AZA treatment in a MDS-derived AML cell line to identify chromatin regulators affecting drug response. We identified the histone acetyl transferase and transcriptional co-activator CBP as a major regulator of AZA sensitivity. Compounds inhibiting the enzymatic activity of CBP synergistically reduced viability of MDS-derived AML cell lines when combined with AZA. Surprisingly, this affect was specific for the RNA-dependent functions of AZA and not observed with the related compound decitabine that is limited to DNA incorporation. The identification of immediate target genes suggested that the effect of CBP inhibition is mediated by downregulation of genes encoding the translational machinery, which could be confirmed in proteomic analysis of nascent proteins. Furthermore, proteins most affected by CBP inhibition include key drivers of cycle progression. Taken together, our results identify a novel synergistic interaction between CBP inhibitors and specifically AZA that warrants further evaluation for the combinatorial treatment of high-risk MDS patients. Beyond the scope of MDS and AZA, we provide novel insight in the function of clinically promising CBP inhibitors that is related to unexpected interference with the translational machinery.

2021-09-22 | PXD021738 | Pride

Inhibition of CBP synergizes with the RNA-dependent mechanisms of azacitidine by limiting protein synthesis

Project description:Inhibition of CBP synergizes with the RNA-dependent mechanisms of azacitidine by limiting protein synthesis

| PRJNA666637 | ENA

Inhibition of CBP synergizes with the RNA-dependent mechanisms of azacitidine by limiting protein synthesis

Project description:Inhibition of CBP synergizes with the RNA-dependent mechanisms of azacitidine by limiting protein synthesis

| PRJNA666398 | ENA

SIRT6-CBP dependent Nuclear Tau Accumulation and its Role in Protein Synthesis.

Project description:Several neurodegenerative diseases present Tau accumulation as the main pathological marker. Tau post-translational modifications such as phosphorylation and acetylation are increased in neurodegenerative patients. Here, we show that Tau hyper-acetylation at residue 174 increases its own nuclear presence and is the result of DNA damage signaling or the lack of SIRT6, both causative of neurodegeneration. Tau-K174ac is deacetylated in the nucleus by SIRT6. However, lack of SIRT6 or chronic DNA damage result in nuclear Tau-K174ac accumulation. Once there, it induces global changes in gene expression affecting protein translation, synthesis and energy production. Concomitantly, AD patients showed increased Nucleolin and a decrease in SIRT6 levels. AD patients present increased levels of nuclear Tau, particularly Tau-K174ac. Our results suggest that increased Tau-K174ac in AD patients is the result of DNA damage signaling and SIRT6 depletion. We propose that Tau-K174ac toxicity is due to its increased stability, nuclear accumulation and nucleolar dysfunction.

2021-04-02 | GSE171342 | GEO

Mechanisms of activity and inhibition of the hepatitis C virus RNA-dependent RNA polymerase.

Project description:The RNA-dependent RNA polymerase NS5B is a key enzyme of the replication of hepatitis C virus (HCV) and a major therapeutic target. Applying a novel continuous assay with highly purified protein and a fluorescent RNA-template we provide for the first time a comprehensive mechanistic description of the enzymatic reaction. Using fluorescence spectroscopy, the kinetics of NS5B was confirmed to consist of two half-reactions, namely substrate binding and turnover. Determining the binding constants of the substrates and the rate constants of individual reaction steps, NS5B was shown to bind the template single-stranded RNA with high affinity (nanomolar range) and in a stepwise process that reflects the substrate positioning. As demonstrated by CD, NTP(s) binding caused a tertiary structural change of the enzyme into an active conformation. The second half-reaction was dissected into a sequential polymerization and a subsequent, rate-limiting product release reaction. Taking advantage of these tools, we analyzed the mechanism of action of the NS5B inhibitor HCV-796, which was shown to interfere with the formation of double-stranded RNA by blocking the second half-reaction.

| S-EPMC2859531 | biostudies-literature

DBC1 Regulates p53 Stability via Inhibition of CBP-Dependent p53 Polyubiquitination.

Project description:The control of p53 protein stability is critical to its tumor suppressor functions. The CREB binding protein (CBP) transcriptional co-activator co-operates with MDM2 to maintain normally low physiological p53 levels in cells via exclusively cytoplasmic E4 polyubiquitination activity. Using mass spectrometry to identify nuclear and cytoplasmic CBP-interacting proteins that regulate compartmentalized CBP E4 activity, we identified deleted in breast cancer 1 (DBC1) as a stoichiometric CBP-interacting protein that negatively regulates CBP-dependent p53 polyubiquitination, stabilizes p53, and augments p53-dependent apoptosis. TCGA analysis demonstrated that solid tumors often retain wild-type p53 alleles in conjunction with DBC1 loss, supporting the hypothesis that DBC1 is selected for disruption during carcinogenesis as a surrogate for p53 functional loss. Because DBC1 maintains p53 stability in the nucleus, where p53 exerts its tumor-suppressive transcriptional function, replacement of DBC1 functionality in DBC1-deleted tumors might enhance p53 function and chemosensitivity for therapeutic benefit.

| S-EPMC6478392 | biostudies-literature

BH3-only protein Bmf mediates apoptosis upon inhibition of CAP-dependent protein synthesis.

Project description:Tight transcriptional regulation, alternative splicing and/or post-translational modifications of BH3-only proteins fine-tune their proapoptotic function. In this study, we characterize the gene locus of the BH3-only protein Bmf (Bcl-2-modifying factor) and describe the generation of two major isoforms from a common transcript in which initiation of protein synthesis involves leucine-coding CUG. Bmf(CUG) and the originally described isoform, Bmf-short, display comparable binding affinities to prosurvival Bcl-2 family members, localize preferentially to the outer mitochondrial membrane and induce rapid Bcl-2-blockable apoptosis. Notably, endogenous Bmf expression is induced on forms of cell stress known to cause repression of the CAP-dependent translation machinery such as serum deprivation, hypoxia, inhibition of the PI3K/AKT pathway or mTOR, as well as direct pharmacological inhibition of the eukaryotic translation initiation factor eIF-4E. Knock down or deletion of Bmf reduces apoptosis under some of these conditions, demonstrating that Bmf can act as a sentinel for stress-impaired CAP-dependent protein translation machinery.

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Quantifying RNA synthesis at rate-limiting steps of transcription using nascent RNA-sequencing data.

Project description:Nascent RNA-sequencing tracks transcription at nucleotide resolution. The genomic distribution of engaged transcription complexes, in turn, uncovers functional genomic regions. Here, we provide analytical steps to (1) identify transcribed regulatory elements de novo genome-wide, (2) quantify engaged transcription complexes at enhancers, promoter-proximal regions, divergent transcripts, gene bodies, and termination windows, and (3) measure distribution of transcription machineries and regulatory proteins across functional genomic regions. This protocol tracks engaged transcription complexes across functional genomic regions demonstrated in human K562 erythroleukemia cells. For complete details on the use and execution of this protocol, please refer to Vihervaara et al. (2021).

| S-EPMC8749334 | biostudies-literature

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