Quantitative analysis of histone demethylase probes using fluorescence polarization

Development of a Fluorescence Polarization Assay for the SARS-CoV-2 Papain-like Protease

The COVID-19 pandemic has caused significant losses to the global community. Although effective vaccination and antiviral therapeutics provide primary defense, SARS-CoV-2 remains a public health threat, given the emerging resistant variants. The SARS-CoV-2 papain-like protease (PLpro) is essential for viral replication and is a promising drug target. We recently designed a series of biarylphenyl PLpro inhibitors with a representative lead Jun12682 showing potent antiviral efficacy in a SARS-CoV-2 infection mouse model. In this study, we designed a fluorescein-labeled biarylphenyl probe Jun12781 and used it to optimize a fluorescence polarization (FP) assay. The FP assay is suitable for high-throughput screening with a Z' factor of 0.69. In addition, we found a positive correlation between the FP binding affinity and the enzymatic inhibitory potency of PLpro inhibitors, suggesting that the FP assay is valid in characterizing the binding affinity of PLpro inhibitors.

The emerging roles of lysine-specific demethylase 4A in cancer: Implications in tumorigenesis and therapeutic opportunities

Lysine-specific demethylase 4 A (KDM4A, also named JMJD2A, KIA0677, or JHDM3A) is a demethylase that can remove methyl groups from histones H3K9me2/3, H3K36me2/3, and H1.4K26me2/me3. Accumulating evidence suggests that KDM4A is not only involved in body homeostasis (such as cell proliferation, migration and differentiation, and tissue development) but also associated with multiple human diseases, especially cancers. Recently, an increasing number of studies have shown that pharmacological inhibition of KDM4A significantly attenuates tumor progression in vitro and in vivo in a range of solid tumors and acute myeloid leukemia. Although there are several reviews on the roles of the KDM4 subfamily in cancer development and therapy, all of them only briefly introduce the roles of KDM4A in cancer without systematically summarizing the specific mechanisms of KDM4A in various physiological and pathological processes, especially in tumorigenesis, which greatly limits advances in the understanding of the roles of KDM4A in a variety of cancers, discovering targeted selective KDM4A inhibitors, and exploring the adaptive profiles of KDM4A antagonists. Herein, we present the structure and functions of KDM4A, simply outline the functions of KDM4A in homeostasis and non-cancer diseases, summarize the role of KDM4A and its distinct target genes in the development of a variety of cancers, systematically classify KDM4A inhibitors, summarize the difficulties encountered in the research of KDM4A and the discovery of related drugs, and provide the corresponding solutions, which would contribute to understanding the recent research trends on KDM4A and advancing the progression of KDM4A as a drug target in cancer therapy.

Identification of potential repurposed drugs for treating endometriosis-associated infertility among women

Endometriosis is the most common gynecological abnormality seen in 10-15% of women of reproductive age, causing infertility in ∼25% of cases, which calls for treatment. Thus, in this study, we have identified miRNAs and genes involved in endometriosis progression, leading to infertility, by performing gene expression analysis followed by pathway analysis and protein-protein networks study. Further, we have predicted repurposed small molecule drugs that will neutralize the regulatory effect of targeting miRNAs that induce sterility in endometriosis. This study predicted two transcription factors, FOXO1, and CREB1, targeted by miRNAs that can be modulated by the repurposed drugs, BRD-K55473186, and methylstat, respectively, for the treatment of infertility due to endometriosis. The former drug seems better and more effective than the other as it showed stronger binding at the active site of FOXO1. These findings provide the rationale for targeting miRNA-regulated transcriptional regulators controlling several biological processes to treat endometriosis and prevent the recurrence of implantation failure or infertility.

Recent Advances with KDM4 Inhibitors and Potential Applications

The histone lysine demethylase 4 (KDM4) family plays an important role in regulating gene transcription, DNA repair, and metabolism. The dysregulation of KDM4 functions is associated with many human disorders, including cancer, obesity, and cardiovascular diseases. Selective and potent KDM4 inhibitors may help not only to understand the role of KDM4 in these disorders but also to provide potential therapeutic opportunities. Here, we provide an overview of the field and discuss current status, challenges, and opportunities lying ahead in the development of KDM4-based anticancer therapeutics.

Discovery of JMJD7 inhibitors with the aid of virtual screening and bioactivity evaluation

Jumonji-C (JmjC) domain-containing 7 (JMJD7), which is a 2-oxoglutarate (2OG)-dependent oxygenase, has been demonstrated to play an important role in the occurrence and development of a number of diseases, particularly cancer. Discovery of JMJD7 inhibitors is thus of great importance. Herein consensus docking/scoring strategy and bioactivity evaluation were used to identify JMJD7 inhibitors from various chemical databases. Seven active compounds were retrieved. The most potent compound, Cpd-3, showed an IC₅₀ value of 6.62 μM against JMJD7. Further biophysical assays confirmed that Cpd-3 could efficiently bind to JMJD7 in vitro. Flexible docking was used to predict the binding mode of Cpd-3 with JMJD7. In a cellular assay, Cpd-3 displayed good inhibitory activity against cancer cell lines expressing a high level of JMJD7. As far as we know, Cpd-3 is the first JMJD7 inhibitor reported so far. Overall, this study established a good starting point for drug discovery targeting JMJD7.

Emerging of lysine demethylases (KDMs): From pathophysiological insights to novel therapeutic opportunities

In recent years, there have been remarkable scientific advancements in the understanding of lysine demethylases (KDMs) because of their demethylation of diverse substrates, including nucleic acids and proteins. Novel structural architectures, physiological roles in the gene expression regulation, and ability to modify protein functions made KDMs the topic of interest in biomedical research. These structural diversities allow them to exert their function either alone or in complex with numerous other bio-macromolecules. Impressive number of studies have demonstrated that KDMs are localized dynamically across the cellular and tissue microenvironment. Their dysregulation is often associated with human diseases, such as cancer, immune disorders, neurological disorders, and developmental abnormalities. Advancements in the knowledge of the underlying biochemistry and disease associations have led to the development of a series of modulators and technical compounds. Given the distinct biophysical and biochemical properties of KDMs, in this review we have focused on advances related to the structure, function, disease association, and therapeutic targeting of KDMs highlighting improvements in both the specificity and efficacy of KDM modulation.

Small molecule KDM4s inhibitors as anti-cancer agents

Histone demethylation is a vital process in epigenetic regulation of gene expression. A number of histone demethylases are present to control the methylated states of histone. Among these enzymes, KDM4s are one subfamily of JmjC KDMs and play important roles in both normal and cancer cells. The discovery of KDM4s inhibitors is a potential therapeutic strategy against different diseases including cancer. Here, we summarize the development of KDM4s inhibitors and some related pharmaceutical information to provide an update of recent progress in KDM4s inhibitors.

Structure-Based Design of a New Scaffold for Cell-Penetrating Peptidic Inhibitors of the Histone Demethylase PHF8

The histone demethylase PHF8 catalyzes demethylation of mono- and di-methylated Lys9 on histone H3 (H3K9me1/2), and is a transcriptional activator involved in the development and cancer. Affinity and specificity of PHF8 towards H3K9me2 is affected by interaction with both the catalytic domain and a PHD reader domain. The latter specifically recognizes tri-methylated Ly4 on histone H3. A fragment of the histone H3 tail with tri-methylated Lys4 was used as a template for the structure-based design of a cyclic, cell-penetrating peptide that exhibits micromolar binding affinity to PHF8 in biochemical assays. The inhibitor has significantly lower affinity towards KDM2 enzymes (the phylogenetically closest subfamily), and to KDM3 and KDM6 subfamilies. Selectivity is only marginal towards an enzyme from the KDM4 family, which shares histone tail specificity with PHF8. It is a substrate of KDM5B, thus implying that the free N terminus is not part of the KDM5 enzyme substrate recognition machinery. The cyclic peptide's ability to penetrate cells is achieved by incorporation of a sequence derived from HIV Tat. The derived cyclic peptide can be used as a starting compound in the search for potent and selective PHF8 inhibitors.

Inhibitors of Protein Methyltransferases and Demethylases

Post-translational modifications of histones by protein methyltransferases (PMTs) and histone demethylases (KDMs) play an important role in the regulation of gene expression and transcription and are implicated in cancer and many other diseases. Many of these enzymes also target various nonhistone proteins impacting numerous crucial biological pathways. Given their key biological functions and implications in human diseases, there has been a growing interest in assessing these enzymes as potential therapeutic targets. Consequently, discovering and developing inhibitors of these enzymes has become a very active and fast-growing research area over the past decade. In this review, we cover the discovery, characterization, and biological application of inhibitors of PMTs and KDMs with emphasis on key advancements in the field. We also discuss challenges, opportunities, and future directions in this emerging, exciting research field.

Recent Progress in Histone Demethylase Inhibitors

There is increasing interest in targeting histone N-methyl-lysine demethylases (KDMs) with small molecules both for the generation of probes for target exploration and for therapeutic purposes. Here we update on previous reviews on the inhibition of the lysine-specific demethylases (LSDs or KDM1s) and JmjC families of N-methyl-lysine demethylases (JmjC KDMs, KDM2-7), focusing on the academic and patent literature from 2014 to date. We also highlight recent biochemical, biological, and structural studies which are relevant to KDM inhibitor development.

A Fluorescence Polarization Biophysical Assay for the Naegleria DNA Hydroxylase Tet1

The discovery of the 5-methylcytosine (5mC) oxidation by the ten–eleven translocation (Tet) protein family was an important advancement in our understanding of DNA-modified epigenetics. Potent inhibitors of these proteins are greatly desired for both the understanding of the functions of these enzymes and to serve as eventual therapeutic leads. So far, the discovery of such small molecules with high affinity has been quite limited. Original tools to screen for activity are greatly needed in order to accelerate this process. Here we present a novel fluorescent probe, and the results of a fluorescence polarization-based binding assay for Naegleria Tet1, a homologue to mammalian Tet. A fluorescence polarization-based competition assay was also established and applied to the rapid and quantitative measurement of the binding affinity of the cofactor αKG and several known Tet1 inhibitors.

Novel Scaffolds of Cell-Active Histone Demethylase Inhibitors Identified from High-Throughput Screening

Jumonji C domain-containing histone demethylases (JHDMs) are epigenetic proteins capable of demethylating methylated lysine residues on histones proteins and for which high-quality chemical probes and eventual therapeutic leads are highly desirable. To expand the extent of known scaffolds targeting JHDMs, we initiated an unbiased high-throughput screening approach using a fluorescence polarization (FP)–based competitive binding assay we recently reported for JHDM1A (aka KDM2A). In total, 14,400 compounds in the HitFinder collection v.11 were screened, which represent all the distinct skeletons of the Maybridge Library. An eventual three compounds with two new scaffolds were discovered and further validated, which not only show in vitro binding for two different JHDMs, JHDM1A and JMJD2A (aka KDM4A), but also induce hypermethylation of their substrate in cells. These represent novel scaffolds as JHDM inhibitors and provide a basis for future optimization of affinity and selectivity.

Development of substrate-selective probes for affinity pulldown of histone demethylases

JmjC-domain containing histone demethylases (JHDMs) play critical roles in many key cellular processes and have been implicated in multiple disease conditions. Each enzyme within this family is known to have a strict substrate scope, specifically the position of the lysine within the histone and its degree of methylation. While much progress has been made in determining the substrates of each enzyme, new methods with which to systematically profile each histone mark are greatly needed. Novel chemical tools have the potential to fill this role and, furthermore, can be used as probes to answer fundamental questions about these enzymes and serve as potential therapeutic leads. In this work, we first investigated three small-molecule probes differing in the degree of “methylation state” and their differential bindings to JHDM1A (an H3K36me1/2 demethylase) using a fluorescence polarization-based competition assay. We then applied this specificity toward the “methylation state” and combined it with specificity toward lysine position in the design and synthesis of a peptidic probe targeting H3K36me2 JHDMs. The probe is further functionalized with a benzophenone cross-linking moiety and a biotin for affinity purification. Results showed binding of the peptidic probe to JHDM1A and specific enrichment of this protein in the presence of its native histone substrates. Affinity purification pulldown experiments from nuclear lysate coupled with mass spectrometry revealed the capability of the probe to pull out and enrich JHDMs along with other epigenetic proteins and transcriptional regulators.

Digging deep into "dirty" drugs - modulation of the methylation machinery

DNA methylation and histone modification are epigenetic mechanisms that result in altered gene expression and cellular phenotype. The exact role of methylation in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) remains unclear. However, aberrations (e.g. loss-/gain-of-function or up-/down-regulation) in components of epigenetic transcriptional regulation in general, and of the methylation machinery in particular, have been implicated in the pathogenesis of these diseases. In addition, many of these components have been identified as therapeutic targets for patients with MDS/AML, and are also being assessed as potential biomarkers of response or resistance to hypomethylating agents (HMAs). The HMAs 5-azacitidine (AZA) and 2'-deoxy-5-azacitidine (decitabine, DAC) inhibit DNA methylation and have shown significant clinical benefits in patients with myeloid malignancies. Despite being viewed as mechanistically similar drugs, AZA and DAC have differing mechanisms of action. DAC is incorporated 100% into DNA, whereas AZA is incorporated into RNA (80-90%) as well as DNA (10-20%). As such, both drugs inhibit DNA methyltransferases (DNMTs; dependently or independently of DNA replication) resulting in the re-expression of tumor-suppressor genes; however, AZA also has an impact on mRNA and protein metabolism via its inhibition of ribonucleotide reductase, resulting in apoptosis. Herein, we first give an overview of transcriptional regulation, including DNA methylation, post-translational histone-tail modifications, the role of micro-RNA and long-range epigenetic gene silencing. We place special emphasis on epigenetic transcriptional regulation and discuss the implication of various components in the pathogenesis of MDS/AML, their potential as therapeutic targets, and their therapeutic modulation by HMAs and other substances (if known). The main focus of this review is laid on dissecting the rapidly evolving knowledge of AZA and DAC with a special focus on their differing mechanisms of action, and the effect of HMAs on transcriptional regulation.

A novel graphene oxide amplified fluorescence anisotropy assay with improved accuracy and sensitivity

A novel and versatile graphene oxide (GO) amplified fluorescence anisotropy (FA) strategy with improved accuracy and sensitivity has been successfully developed.