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Gill JK, Shaw GS. Using Förster Resonance Energy Transfer (FRET) to Understand the Ubiquitination Landscape. Chembiochem 2024:e202400193. [PMID: 38632088 DOI: 10.1002/cbic.202400193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 04/15/2024] [Accepted: 04/17/2024] [Indexed: 04/19/2024]
Abstract
Förster resonance energy transfer (FRET) is a fluorescence technique that allows quantitative measurement of protein interactions, kinetics and dynamics. This review covers the use of FRET to study the structures and mechanisms of ubiquitination and related proteins. We survey FRET assays that have been developed where donor and acceptor fluorophores are placed on E1, E2 or E3 enzymes and ubiquitin (Ub) to monitor steady-state and real-time transfer of Ub through the ubiquitination cascade. Specialized FRET probes placed on Ub and Ub-like proteins have been developed to monitor Ub removal by deubiquitinating enzymes (DUBs) that result in a loss of a FRET signal upon cleavage of the FRET probes. FRET has also been used to understand conformational changes in large complexes such as multimeric E3 ligases and the proteasome, frequently using sophisticated single molecule methods. Overall, FRET is a powerful tool to help unravel the intricacies of the complex ubiquitination system.
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Affiliation(s)
- Jashanjot Kaur Gill
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, N6A5C1
| | - Gary S Shaw
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, N6A5C1
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2
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Zessin M, Meleshin M, Hilscher S, Schiene-Fischer C, Barinka C, Jung M, Schutkowski M. Continuous Fluorescent Sirtuin Activity Assay Based on Fatty Acylated Lysines. Int J Mol Sci 2023; 24:ijms24087416. [PMID: 37108579 PMCID: PMC10138348 DOI: 10.3390/ijms24087416] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/06/2023] [Accepted: 04/10/2023] [Indexed: 04/29/2023] Open
Abstract
Lysine deacetylases, like histone deacetylases (HDACs) and sirtuins (SIRTs), are involved in many regulatory processes such as control of metabolic pathways, DNA repair, and stress responses. Besides robust deacetylase activity, sirtuin isoforms SIRT2 and SIRT3 also show demyristoylase activity. Interestingly, most of the inhibitors described so far for SIRT2 are not active if myristoylated substrates are used. Activity assays with myristoylated substrates are either complex because of coupling to enzymatic reactions or time-consuming because of discontinuous assay formats. Here we describe sirtuin substrates enabling direct recording of fluorescence changes in a continuous format. Fluorescence of the fatty acylated substrate is different when compared to the deacylated peptide product. Additionally, the dynamic range of the assay could be improved by the addition of bovine serum albumin, which binds the fatty acylated substrate and quenches its fluorescence. The main advantage of the developed activity assay is the native myristoyl residue at the lysine side chain avoiding artifacts resulting from the modified fatty acyl residues used so far for direct fluorescence-based assays. Due to the extraordinary kinetic constants of the new substrates (KM values in the low nM range, specificity constants between 175,000 and 697,000 M-1s-1) it was possible to reliably determine the IC50 and Ki values for different inhibitors in the presence of only 50 pM of SIRT2 using different microtiter plate formats.
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Affiliation(s)
- Matthes Zessin
- Department of Medicinal Chemistry, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, 06120 Halle, Germany
| | - Marat Meleshin
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, 06120 Halle, Germany
| | - Sebastian Hilscher
- Department of Medicinal Chemistry, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, 06120 Halle, Germany
| | - Cordelia Schiene-Fischer
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, 06120 Halle, Germany
| | - Cyril Barinka
- Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, Prumyslova 595, 25250 Vestec, Czech Republic
| | - Manfred Jung
- Institute of Pharmaceutical Sciences, University of Freiburg, Albertstraße 25, 79104 Freiburg, Germany
| | - Mike Schutkowski
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, 06120 Halle, Germany
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3
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Zessin M, Meleshin M, Simic Z, Kalbas D, Arbach M, Gebhardt P, Melesina J, Liebscher S, Bordusa F, Sippl W, Barinka C, Schutkowski M. Continuous Sirtuin/HDAC (histone deacetylase) activity assay using thioamides as PET (Photoinduced Electron Transfer)-based fluorescence quencher. Bioorg Chem 2021; 117:105425. [PMID: 34695733 DOI: 10.1016/j.bioorg.2021.105425] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 10/07/2021] [Accepted: 10/09/2021] [Indexed: 12/28/2022]
Abstract
Histone deacylase 11 and human sirtuins are able to remove fatty acid-derived acyl moieties from the ε-amino group of lysine residues. Specific substrates are needed for investigating the biological functions of these enzymes. Additionally, appropriate screening systems are required for identification of modulators of enzymatic activities of HDAC11 and sirtuins. We designed and synthesized a set of activity probes by incorporation of a thioamide quencher unit into the fatty acid-derived acyl chain and a fluorophore in the peptide sequence. Systematic variation of both fluorophore and quencher position resulted "super-substrates" with catalytic constants of up to 15,000,000 M-1s-1 for human sirtuin 2 (Sirt2) enabling measurements using enzyme concentrations down to 100 pM in microtiter plate-based screening formats. It could be demonstrated that the stalled intermediate formed by the reaction of Sirt2-bound thiomyristoylated peptide and NAD+ has IC50 values below 200 pM.
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Affiliation(s)
- Matthes Zessin
- Department of Medicinal Chemistry, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Marat Meleshin
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Zeljko Simic
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Diana Kalbas
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Miriam Arbach
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Philip Gebhardt
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Jelena Melesina
- Department of Medicinal Chemistry, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Sandra Liebscher
- Department of Natural Product Biochemistry, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Frank Bordusa
- Department of Natural Product Biochemistry, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Wolfgang Sippl
- Department of Medicinal Chemistry, Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
| | - Cyril Barinka
- Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic
| | - Mike Schutkowski
- Department of Enzymology, Charles Tanford Protein Center, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany.
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4
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Rossi R, Ciofalo M. Current Advances in the Synthesis and Biological Evaluation of Pharmacologically Relevant 1,2,4,5-Tetrasubstituted-1H-Imidazole Derivatives. CURR ORG CHEM 2019. [DOI: 10.2174/1385272823666191014154129] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
:
In recent years, the synthesis and evaluation of the
biological properties of 1,2,4,5-tetrasubstituted-1H-imidazole
derivatives have been the subject of a large number of studies
by academia and industry. In these studies it has been shown
that this large and highly differentiated class of heteroarene
derivatives includes high valuable compounds having important
biological and pharmacological properties such as
antibacterial, antifungal, anthelmintic, anti-inflammatory, anticancer,
antiviral, antihypertensive, cholesterol-lowering, antifibrotic,
antiuricemic, antidiabetic, antileishmanial and antiulcer
activities.
:
The present review with 411 references, in which we focused on the literature data published mainly from 2011
to 2017, aims to update the readers on the recent developments on the synthesis and biological evaluation of
pharmacologically relevant 1,2,4,5-tetrasubstituted-1H-imidazole derivatives with an emphasis on their different
molecular targets and their potential use as drugs to treat various types of diseases. Reference was also
made to substantial literature data acquired before 2011 in this burgeoning research area.
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Affiliation(s)
- Renzo Rossi
- Dipartimento di Chimica e Chimica Industriale, University of Pisa - via Moruzzi, 3, I-56124 Pisa, Italy
| | - Maurizio Ciofalo
- Dipartimento di Scienze Agrarie, Alimentari e Forestali, University of Palermo - Viale delle Scienze, Edificio 4, I-90128 Palermo, Italy
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5
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Kutil Z, Mikešová J, Zessin M, Meleshin M, Nováková Z, Alquicer G, Kozikowski A, Sippl W, Bařinka C, Schutkowski M. Continuous Activity Assay for HDAC11 Enabling Reevaluation of HDAC Inhibitors. ACS OMEGA 2019; 4:19895-19904. [PMID: 31788622 PMCID: PMC6882135 DOI: 10.1021/acsomega.9b02808] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 10/18/2019] [Indexed: 05/05/2023]
Abstract
Histone deacetylase 11 (HDAC11) preferentially removes fatty acid residues from lysine side chains in a peptide or protein environment. Here, we report the development and validation of a continuous fluorescence-based activity assay using an internally quenched TNFα-derived peptide derivative as a substrate. The threonine residue in the +1 position was replaced by the quencher amino acid 3'-nitro-l-tyrosine and the fatty acyl moiety substituted by 2-aminobenzoylated 11-aminoundecanoic acid. The resulting peptide substrate enables fluorescence-based direct and continuous readout of HDAC11-mediated amide bond cleavage fully compatible with high-throughput screening formats. The Z'-factor is higher than 0.85 for the 15 μM substrate concentration, and the signal-to-noise ratio exceeds 150 for 384-well plates. In the absence of NAD+, this substrate is specific for HDAC11. Reevaluation of inhibitory data using our novel assay revealed limited potency and selectivity of known HDAC inhibitors, including Elevenostat, a putative HDAC11-specific inhibitor.
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Affiliation(s)
- Zsófia Kutil
- Institute
of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic
| | - Jana Mikešová
- Institute
of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic
| | - Matthes Zessin
- Department
of Medicinal Chemistry, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Marat Meleshin
- Department
of Enzymology, Institute of Biochemistry and Biotechnology, Charles
Tanford Protein Centre, Martin Luther University
Halle-Wittenberg, Kurt-Mothes-Straße
3a, 06120 Halle
(Saale), Germany
| | - Zora Nováková
- Institute
of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic
| | - Glenda Alquicer
- Institute
of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic
| | - Alan Kozikowski
- StarWise
Therapeutics LLC, 505
S Rosa Road, Suite 27, Madison, Wisconsin 53719-1235, United States
| | - Wolfgang Sippl
- Department
of Medicinal Chemistry, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Cyril Bařinka
- Institute
of Biotechnology of the Czech Academy of Sciences, BIOCEV, Prumyslova 595, 252 50 Vestec, Czech Republic
- E-mail: . Tel.: +420-325-873-777 (C.B.)
| | - Mike Schutkowski
- Department
of Enzymology, Institute of Biochemistry and Biotechnology, Charles
Tanford Protein Centre, Martin Luther University
Halle-Wittenberg, Kurt-Mothes-Straße
3a, 06120 Halle
(Saale), Germany
- E-mail: . Tel.: +49-345-5524-828 (M.S.)
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Zessin M, Kutil Z, Meleshin M, Nováková Z, Ghazy E, Kalbas D, Marek M, Romier C, Sippl W, Bařinka C, Schutkowski M. One-Atom Substitution Enables Direct and Continuous Monitoring of Histone Deacylase Activity. Biochemistry 2019; 58:4777-4789. [PMID: 31682411 DOI: 10.1021/acs.biochem.9b00786] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We developed a one-step direct assay for the determination of histone deacylase (HDAC) activity by substituting the carbonyl oxygen of the acyl moiety with sulfur, resulting in thioacylated lysine side chains. This modification is recognized by class I HDACs with different efficiencies ranging from not accepted for HDAC1 to kinetic constants similar to that of the parent oxo substrate for HDAC8. Class II HDACs can hydrolyze thioacylated substrates with approximately 5-10-fold reduced kcat values, which resembles the effect of thioamide substitution in metallo-protease substrates. Class IV HDAC11 accepts thiomyristoyl modification less efficiently with an ∼5-fold reduced specificity constant. On the basis of the unique spectroscopic properties of thioamide bonds (strong absorption in spectral range of 260-280 nm and efficient fluorescence quenching), HDAC-mediated cleavage of thioamides could be followed by ultraviolet-visible and fluorescence spectroscopy in a continuous manner. The HDAC activity assay is compatible with microtiter plate-based screening formats up to 1536-well plates with Z' factors of >0.75 and signal-to-noise ratios of >50. Using thioacylated lysine residues in p53-derived peptides, we optimized substrates for HDAC8 with a catalytic efficiency of >250000 M-1 s-1, which are more than 100-fold more effective than most of the known substrates. We determined inhibition constants of several inhibitors for human HDACs using thioacylated peptidic substrates and found good correlation with the values from the literature. On the other hand, we could introduce N-methylated, N-acylated lysine residues as inhibitors for HDACs with an IC50 value of 1 μM for an N-methylated, N-myristoylated peptide derivative and human HDAC11.
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Affiliation(s)
- Matthes Zessin
- Department of Medicinal Chemistry, Institute of Pharmacy , Martin-Luther-University Halle-Wittenberg , 06120 Halle/Saale , Germany
| | - Zsófia Kutil
- Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV , Prumyslova 595 , 252 50 Vestec , Czech Republic
| | - Marat Meleshin
- Department of Enzymology, Institute of Biochemistry and Biotechnology, Charles-Tanford-Protein Center , Martin-Luther-University Halle-Wittenberg , 06120 Halle/Saale , Germany
| | - Zora Nováková
- Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV , Prumyslova 595 , 252 50 Vestec , Czech Republic
| | - Ehab Ghazy
- Department of Medicinal Chemistry, Institute of Pharmacy , Martin-Luther-University Halle-Wittenberg , 06120 Halle/Saale , Germany
| | - Diana Kalbas
- Department of Enzymology, Institute of Biochemistry and Biotechnology, Charles-Tanford-Protein Center , Martin-Luther-University Halle-Wittenberg , 06120 Halle/Saale , Germany
| | - Martin Marek
- Departement de Biologie Structurale Integrative, Institut de Genetique et Biologie Moleculaire et Cellulaire (IGBMC) , Universite de Strasbourg (UDS), CNRS, INSERM , 1 rue Laurent Fries, B.P. 10142 , 67404 Illkirch Cedex IGBMC, France
| | - Christophe Romier
- Departement de Biologie Structurale Integrative, Institut de Genetique et Biologie Moleculaire et Cellulaire (IGBMC) , Universite de Strasbourg (UDS), CNRS, INSERM , 1 rue Laurent Fries, B.P. 10142 , 67404 Illkirch Cedex IGBMC, France
| | - Wolfgang Sippl
- Department of Medicinal Chemistry, Institute of Pharmacy , Martin-Luther-University Halle-Wittenberg , 06120 Halle/Saale , Germany
| | - Cyril Bařinka
- Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV , Prumyslova 595 , 252 50 Vestec , Czech Republic
| | - Mike Schutkowski
- Department of Enzymology, Institute of Biochemistry and Biotechnology, Charles-Tanford-Protein Center , Martin-Luther-University Halle-Wittenberg , 06120 Halle/Saale , Germany
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7
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Wild-type p53 oligomerizes more efficiently than p53 hot-spot mutants and overcomes mutant p53 gain-of-function via a "dominant-positive" mechanism. Oncotarget 2018; 9:32063-32080. [PMID: 30174797 PMCID: PMC6112834 DOI: 10.18632/oncotarget.25944] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 07/21/2018] [Indexed: 12/24/2022] Open
Abstract
Human p53 protein acts as a transcription factor predominantly in a tetrameric form. Single residue changes, caused by hot-spot mutations of the TP53 gene in human cancer, transform wild-type (wt) p53 tumor suppressor proteins into potent oncoproteins - with gain-of-function, tumor-promoting activity. Oligomerization of p53 allows for a direct interplay between wt and mutant p53 proteins if both are present in the same cells - where a mutant p53's dominant-negative effect known to inactivate wt p53, co-exists with an opposite mechanism - a "dominant-positive" suppression of the mutant p53's gain-of-function activity by wt p53. In this study we determine the oligomerization efficiency of wt and mutant p53 in living cells using FRET-based assays and describe wt p53 to be more efficient than mutant p53 in entering p53 oligomers. The biased p53 oligomerization helps to interpret earlier reports of a low efficiency of the wt p53 inactivation via the dominant-negative effect, while it also implies that the "dominant-positive" effect may be more pronounced. Indeed, we show that at similar wt:mutant p53 concentrations in cells - the mutant p53 gain-of-function stimulation of gene transcription and cell migration is more efficiently inhibited than the wt p53's tumor-suppressive transactivation and suppression of cell migration. These results suggest that the frequent mutant p53 accumulation in human tumor cells does not only directly strengthen its gain-of-function activity, but also protects the oncogenic p53 mutants from the functional dominance of wt p53.
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8
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Schutkowski M, Fischer F, Roessler C, Steegborn C. New assays and approaches for discovery and design of Sirtuin modulators. Expert Opin Drug Discov 2014; 9:183-99. [DOI: 10.1517/17460441.2014.875526] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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9
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Quinn AM, Simeonov A. Methods for Activity Analysis of the Proteins that Regulate Histone Methylation. CURRENT CHEMICAL GENOMICS 2011; 5:95-105. [PMID: 21966349 PMCID: PMC3180180 DOI: 10.2174/1875397301005010095] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 03/23/2011] [Accepted: 04/25/2011] [Indexed: 12/20/2022]
Abstract
The enzymes that regulate histone methylation states and the protein domains that recognize methylated histone residues have been implicated in a number of human diseases, including cancer, as a result of their ability to affect transcriptional changes by altering chromatin structure. These proteins are recognized as potential therapeutic targets for the treatment of diseases associated with epigenetic disruption; however, few inhibitors of their activity have been identified. The majority of histone demethylase and methyltransferase enzyme inhibitors have been discovered on the basis of their structural similarity to substrates or known inhibitors of enzymes with analogous mechanisms. The general lack of potency and specificity of these compounds indicates that novel chemotypes are needed to address the large number of recently discovered histone-modifying enzymes. High-throughput screening (HTS) allows rapid testing of chemically diverse small molecule libraries, provided assays amenable to HTS exist. Here we review the biochemical and cellular assays available for testing the proteins and enzymes that regulate histone methylation. Progress in the development of high-throughput, sensitive, and robust assays will enable discovery of small molecules for epigenetic therapy.
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Affiliation(s)
- Amy M Quinn
- NIH Chemical Genomics Center, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892-3370, USA
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Wang K, Yang R, Xu J, Zhang Y, Zhu L, Lin J, Huang B. DEVELOPMENT OF AN ALPHASCREEN-BASED HIGH-THROUGHPUT SCREENING ASSAY FOR INHIBITORS OF HUMAN VASCULAR ENDOTHELIAL GROWTH FACTOR RECEPTOR-3. J Immunoassay Immunochem 2011; 32:219-32. [DOI: 10.1080/15321819.2011.559296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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11
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Robers MB, Loh C, Carlson CB, Yang H, Frey EA, Hermanson SB, Bi K. Measurement of the cellular deacetylase activity of SIRT1 on p53 via LanthaScreen® technology. MOLECULAR BIOSYSTEMS 2010; 7:59-66. [PMID: 20931131 DOI: 10.1039/c0mb00026d] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Upon genomic insult, the tumor suppressor p53 is phosphorylated and acetylated at specific serine and lysine residues, increasing its stability and transactivation function. Deacetylases, including the type III histone deacetylase SIRT1, remove acetyl groups from p53 and counterbalance acetyltransferase activity during a DNA damage response. This report describes a series of high-throughput LanthaScreen® time-resolved Förster resonance energy transfer (TR-FRET) immunoassays for detection of intracellular p53 phosphorylation of Ser15 and acetylation of Lys382 upon treatment with DNA damage agents, such as etoposide. These assays were used to measure the deacetylase activity of SIRT1 and/or Type I/II Histone deacetylases (HDACs). First, BacMam-mediated overexpression of SIRT1 resulted in dose-dependent deacetylation of GFP-p53 following etoposide treatment of U-2 OS cells, confirming that GFP-p53 serves as a SIRT1 substrate in this assay format. Further, overexpression of the acetyltransferase p300 via BacMam increased the acetylation of GFP-p53 at Lys382. Next, siRNA-mediated knockdown of SIRT1 resulted in increased GFP-p53 acetylation, indicating that endogenous SIRT1 activity can also be measured in U-2 OS cells. Consistent with these results, GFP-p53 acetylation was also increased upon treatment of cells with a small-molecule inhibitor of SIRT1, EX-527. The effect of this compound was dramatically increased when used in combination with chemotherapeutic drug and/or the HDAC inhibitor Trichostatin A, confirming a proposed synergistic mechanism of p53 deacetylation by SIRT1 and Type I/II HDACs. Taken together, the cellular assays described here can be used as high-throughput alternatives to traditional immunoassays such as western blotting for identifying pharmacological modulators of specific p53-modifying enzymes.
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Affiliation(s)
- Matthew B Robers
- Discovery Assays and Services, Life Technologies Corporation, Madison, WI 53719, USA
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