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Suppression of p53 response by blocking p53-Mediator binding with a stapled peptide

ABSTRACT: DNA-binding transcription factors (TFs) have been challenging to target with molecular probes. Many TFs function in part through interaction with Mediator; we sought to block p53 function by disrupting the p53-Mediator interaction. Through rational design and activity-based screening, we characterized a stapled peptide, with functional mimics of both p53 activation domains, that selectively disrupted p53- and Mediator-dependent transcription in vitro. This “bivalent peptide” also suppressed p53 transcriptional response in human cancer cells. Our strategy circumvents the TF and instead targets the TF-Mediator interface, with desired transcriptional outcomes. Different TFs target Mediator through different subunits, suggesting this strategy could be generalizable.

ORGANISM(S): Homo sapiens

PROVIDER: GSE193418 | GEO | 2022/04/05

REPOSITORIES: GEO

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Suppression of p53 response by blocking p53–Mediator binding with a stapled peptide

Project description:DNA-binding transcription factors (TFs) have been challenging to target with molecular probes. Many TFs function in part through interaction with Mediator; we sought to block p53 function by disrupting the p53-Mediator interaction. Through rational design and activity-based screening, we characterized a stapled peptide, with functional mimics of both p53 activation domains, that selectively disrupted p53- and Mediator-dependent transcription in vitro. This “bivalent peptide” also suppressed p53 transcriptional response in human cancer cells. Our strategy circumvents the TF and instead targets the TF-Mediator interface, with desired transcriptional outcomes. Different TFs target Mediator through different subunits, suggesting this strategy could be generalizable.

2020-08-01 | GSE135870 | GEO

Suppression of p53 response by blocking p53-Mediator binding with a stapled peptide

Project description:Suppression of p53 response by blocking p53-Mediator binding with a stapled peptide

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Suppression of p53 response by blocking p53–Mediator binding with a stapled peptide

Project description:Suppression of p53 response by blocking p53–Mediator binding with a stapled peptide

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A cell-permeable stapled peptide inhibitor of the estrogen receptor/coactivator interaction

Project description:We and others have proposed that coactivator binding inhibitors, which block the interaction of estrogen receptor and steroid receptor coactivators, may represent a potential class of new breast cancer therapeutics. The development of coactivator binding inhibitors has been limited, however, because many of the current molecules which are active in in vitro and biochemical assays are not active in cell-based assays. Our goal in this work was to prepare a coactivator binding inhibitor active in cellular models of breast cancer. To accomplish this, we used molecular dynamics simulations to convert a high-affinity stapled peptide with poor cell permeability into R4K1, a cell-penetrating stapled peptide. R4K1 displays high binding affinity for estrogen receptor ɑ, inhibits the formation of estrogen receptor/coactivator complexes, and distributes throughout the cell with a high percentage of nuclear localization. R4K1 represses native gene transcription mediated by estrogen receptor ɑ and inhibits proliferation of estradiol-stimulated MCF-7 cells. Using RNA-Seq, we demonstrate that almost all of the effects of R4K1 on global gene transcription are estrogen receptor-associated. This chemical probe provides a significant proof-of-concept for preparing cell-permeable stapled peptide inhibitors of the estrogen receptor/coactivator interaction.

2018-01-09 | GSE108308 | GEO

Time-series transcriptomics and proteomics reveal alternative modes to decode p53 oscillations

Project description:Transcription factors (TFs) can relay signals through temporal alterations in their levels. The cell stress responsive TF p53 exhibits different dynamics depending on the type of stress, which influence the magnitude and dynamics of expression of its target genes and subsequent cellular outcomes. The mechanisms decoding p53 dynamics into levels and dynamics of RNA and protein of its targets remain unclear. We systematically quantified p53 target mRNA and protein levels over time under two p53 dynamical regimes – oscillatory and sustained – using RNA-seq and quantitative mass spectrometry. We categorized the mRNA dynamical patterns arising from oscillatory or sustained p53 expression, as well as the corresponding protein dynamics. We found that in both cases oscillatory dynamics allowed for the greatest variety of dynamical patterns of the downstream species. Target proteins from a wide range of functional categories were induced under both p53 dynamic conditions, with induction levels being overall higher under sustained dynamics. Mathematical modeling combined with analysis of empirical data revealed three mechanisms of decoding p53 dynamics: adjustment of mRNA and protein degradation rates, adjustment of activation thresholds for expression of mRNA and corresponding protein levels, and usage of coherent and incoherent feed-forward loop motifs in generating exclusive responses to p53 oscillatory or sustained dynamics, respectively. Our results highlight the diversity of mechanisms that decode complex TF dynamics into dynamical patterns of mRNA and proteins.

2022-02-11 | PXD027030 | Pride

Stapled peptide inhibitors of RAB25 target context-specific phenotypes in cancer

Project description:The Ras-family small GTPase RAB25 is involved in numerous aspects of endosomal protein trafficking and cell polarity. Recent evidence has established a role for RAB25, as well as related RAB-family and effector proteins, in oncogenic signaling, highlighting the need for chemical probes targeting this class of proteins. Here we report the development of all-hydrocarbon stabilized peptides targeting RAB25 derived from the RAB-binding FIP-family of proteins. Relative to unmodified FIP peptides, optimized stapled peptides show markedly increased structural stability, binding affinity, cell permeability and inhibition of RAB25:FIP complex formation. RAB25 expression has been shown to promote both pro- and anti-oncogenic phenotypes in specific cellular contexts. Stapled peptide RFP14 treatment of breast and ovarian cancer cell lines, in which RAB25 is pro-oncogenic, inhibited migration and proliferation in a RAB25-dependent manner. In contrast, treatment of a triple-negative breast cancer cell line in which RAB25 is tumor suppressive augmented proliferation and migration. Gene expression (RNA Seq) profiling identified significantly altered transcripts in response to RAB25 expression in ovarian cancer cells, and treatment with the optimized stapled peptide RFP14 reversed this expression profile. These data validate first-in-class chemical probes targeting RAB-family proteins and support the role of RAB25 in regulating context-specific oncogenic phenotypes.

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Readout of histone methylation by Trim24 locally restricts chromatin opening by p53

Project description:The genomic binding sites of the transcription factor (TF) and tumour suppressor p53 are unusually diverse in regards to their chromatin features, including histone modifications, opening the possibility that chromatin provides context-dependence for p53 regulation. Here, we show that the ability of p53 to open chromatin and activate its target genes is indeed locally restricted by its cofactor Trim24. Trim24 binds to both p53 and unmethylated lysine 4 of histone H3, thereby preferentially locating to those p53 sites that reside in closed chromatin, while it is deterred from accessible chromatin by lysine 4 methylation. The presence of Trim24 increases cell viability upon stress and enables p53 to impact gene expression as a function of the local chromatin state. These findings link histone methylation to p53 function and illustrate how specificity in chromatin can be achieved, not by TF-intrinsic sensitivity to histone modifications, but by employing chromatin-sensitive cofactors which locally modulate TF function.

2023-05-05 | PXD039553 | Pride

A cell-permeable stapled peptide inhibitor of the estrogen receptor/coactivator interaction

Project description:A cell-permeable stapled peptide inhibitor of the estrogen receptor/coactivator interaction

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A mammalian transcription factor-specific peptide repository for targeted proteomics

Project description:Site-specific transcription factors (TFs) play an essential role in mammalian development and function as they are vital for the majority of cellular processes. Despite their biological importance, TF proteomic data is scarce in the literature, likely due to difficulties in detecting peptides as the abundance of TFs in cells tends to be low. In recent years, significant improvements in mass spectrometry (MS)-based technologies in terms of sensitivity and specificity have increased the interest in developing quantitative methodologies specifically targeting relatively lowly abundant proteins such as TFs in mammalian models. Such efforts would be greatly aided by the availability of TF peptide-specific information as such data would not only enable improvements in speed and accuracy of protein identifications, but also ameliorate cross-comparisons of quantitative proteomics data and allow for a more efficient development of targeted proteomics assays. However, to date, no comprehensive TF proteotypic peptide database has been developed. To address this evident lack of TF peptide data in public repositories, we are generating a comprehensive, experimentally derived TF proteotypic peptide spectral library dataset based on in vitro protein expression. Our library currently contains peptide information for 89 TFs, and this number is set to increase in the near future.

2015-01-23 | PXD001212 | Pride

USP15-dependent lysosomal pathway controls p53-R175H turnover in ovarian cancer cells

Project description:Gain-of-function p53 mutants such as p53-R175H form stable aggregates that accumulate in cells and play an important role in cancer progression. Selective degradation of gain-of-function p53 mutants has emerged as a highly attractive therapeutic strategy to target cancer cells harboring specific p53 mutations. We identified a small molecule called MCB-613 to cause rapid ubiquitination, nuclear export, and degradation of p53-R175H through lysosome-mediated pathway leading to catastrophic cancer cell death. In contrast to its effect on the p53-R175H mutant, MCB-613 causes slight stabilization of p53-WT and has weaker effects on other p53 gain-of-function mutants. Using state-of-the-art genetic and chemical approaches, we identified the deubiquitinase USP15 as the mediator of MCB-613’s effect on p53-R175H and established USP15 as a selective upstream regulator of p53-R175H in ovarian cancer cells. These results confirm that distinct pathways regulate the turnover of p53-WT and the different p53 mutants and open new opportunities to selectively target them.

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