Nucleosomes and Epigenetics from a Chemical Perspective

HIST3H2A promotes the progression of prostate cancer through inhibiting cell necroptosis

In recent years, there has been an increase in the incidence and mortality rates of prostate cancer (PCa). However, the specific molecular mechanisms underlying its occurrence and development remain unclear, necessitating the identification of new therapeutic targets. Through bioinformatics analysis, we discovered a previously unstudied differential gene called HIST3H2A in prostate cancer. Our study revealed that HIST3H2A is highly expressed in PCa tissues, as confirmed by analysis of both the GEO and UALCAN databases. Further analysis using the KEGG database demonstrated that HIST3H2A regulates the pathway of programmed necroptosis in cells. Additionally, we observed significant up-regulation of HIST3H2A in PCa tissues and cell lines. HIST3H2A was found to regulate cell proliferation, migration, invasion, and the epithelial-mesenchymal transition (EMT) process in tumors. Notably, HIST3H2A's role in regulating programmed necroptosis in prostate cancer cells differs from its role in apoptosis. In vitro and in vivo experiments collectively support the key role of HIST3H2A in promoting the development of prostate cancer, highlighting its potential as a therapeutic target for patients with PCa.

Unveiling the epigenetic landscape of plants using flow cytometry approach

Plants are sessile creatures that have to adapt constantly changing environmental circumstances. Plants are subjected to a range of abiotic stressors as a result of unpredictable climate change. Understanding how stress-responsive genes are regulated can help us better understand how plants can adapt to changing environmental conditions. Epigenetic markers that dynamically change in response to stimuli, such as DNA methylation and histone modifications are known to regulate gene expression. Individual cells or particles' physical and/or chemical properties can be measured using the method known as flow cytometry. It may therefore be used to evaluate changes in DNA methylation, histone modifications, and other epigenetic markers, making it a potent tool for researching epigenetics in plants. We explore the use of flow cytometry as a technique for examining epigenetic traits in this thorough discussion. The separation of cell nuclei and their subsequent labeling with fluorescent antibodies, offering information on the epigenetic mechanisms in plants when utilizing flow cytometry. We also go through the use of high-throughput data analysis methods to unravel the complex epigenetic processes occurring inside plant systems.

Mechanistic Insights into Harmine-Mediated Inhibition of Human DNA Methyltransferases and Prostate Cancer Cell Growth

Mammalian DNA methyltransferases (DNMTs), including DNMT1, DNMT3A, and DNMT3B, are key DNA methylation enzymes and play important roles in gene expression regulation. Dysregulation of DNMTs is linked to various diseases and carcinogenesis, and therefore except for the two approved anticancer azanucleoside drugs, various non-nucleoside DNMT inhibitors have been identified and reported. However, the underlying mechanisms for the inhibitory activity of these non-nucleoside inhibitors still remain largely unknown. Here, we systematically tested and compared the inhibition activities of five non-nucleoside inhibitors toward the three human DNMTs. We found that harmine and nanaomycin A blocked the methyltransferase activity of DNMT3A and DNMT3B more efficiently than resveratrol, EGCG, and RG108. We further determined the crystal structure of harmine in complex with the catalytic domain of the DNMT3B-DNMT3L tetramer revealing that harmine binds at the adenine cavity of the SAM-binding pocket in DNMT3B. Our kinetics assays confirm that harmine competes with SAM to competitively inhibit DNMT3B-3L activity with a Ki of 6.6 μM. Cell-based studies further show that harmine treatment inhibits castration-resistant prostate cancer cell (CRPC) proliferation with an IC50 of ∼14 μM. The CPRC cells treated with harmine resulted in reactivating silenced hypermethylated genes compared to the untreated cells, and harmine cooperated with an androgen antagonist, bicalutamide, to effectively inhibit the proliferation of CRPC cells. Our study thus reveals, for the first time, the inhibitory mechanism of harmine on DNMTs and highlights new strategies for developing novel DNMT inhibitors for cancer treatment.

Evaluation by Experimentation and Simulation of a FRET Pair Comprising Fluorescent Nucleobase Analogs in Nucleosomes

Förster resonance energy transfer (FRET) is an attractive tool for understanding biomolecular dynamics. FRET-based analysis of nucleosomes has the potential to fill the knowledge gaps between static structures and dynamic cellular behaviors. Compared with typical FRET pairs using bulky fluorophores introduced by flexible linkers, fluorescent nucleoside-based FRET pair has great potential since it can be fitted within the helical structures of nucleic acids. Herein we report on the construction of nucleosomes containing a nucleobase FRET pair and the investigation of experimental and theoretical FRET efficiencies through steady-state fluorescence spectroscopy and calculation based on molecular dynamics simulations, respectively. Distinguishable experimental FRET efficiencies were observed depending on the positions of FRET pairs in nucleosomal DNA. The tendency could be supported by theoretical study. This work suggests the possibility of our approach to analyze structural changes of nucleosomes by epigenetic modifications or internucleosomal interactions.

RNAPII driven post-translational modifications of nucleosomal histones

The current understanding of how specific distributions of histone post-translational modifications (PTMs) are achieved throughout the chromatin remains incomplete. This review focuses on the role of RNA polymerase II (RNAPII) in establishing H2BK120/K123 ubiquitination and H3K4/K36 methylation distribution. The rate of RNAPII transcription is mainly a function of the RNAPII elongation and recruitment rates. Two major mechanisms link RNAPII's transcription rate to the distribution of PTMs. First, the phosphorylation patterns of Ser2P/Ser5P in the C-terminal domain of RNAPII change as a function of time, since the start of elongation, linking them to the elongation rate. Ser2P/Ser5P recruits specific histone PTM enzymes/activators to the nucleosome. Second, multiple rounds of binding and catalysis by the enzymes are required to establish higher methylations (H3K4/36me3). Thus, methylation states are determined by the transcription rate. In summary, the first mechanism determines the location of methylations in the gene, while the second mechanism determines the methylation state.

Participation of Histones in DNA Damage and Repair within Nucleosome Core Particles: Mechanism and Applications

DNA is damaged by various endogenous and exogenous sources, leading to a diverse group of reactive intermediates that yield a complex mixture of products. The initially formed products are often metastable and can react to yield lesions that are more biologically deleterious. Mechanistic studies are frequently carried out on free DNA as the substrate. The observations do not necessarily reflect the reaction environment inside human cells where genomic DNA is condensed as chromatin in the nucleus. Chromatin is made up of monomeric structural units called nucleosomes, which are comprised of DNA wrapped around an octameric core of histone proteins (two copies each of histones H2A, H2B, H3, and H4).This account presents a summary of our work in the past decade on the mechanistic studies of DNA damage and repair in reconstituted nucleosome core particles (NCPs). A series of metastable lesions and reactive intermediates, such as abasic sites (AP), N7-methyl-2'-deoxyguanosine (MdG), and 2'-deoxyadenosin-N6-yl radical (dA^•), have been independently generated in a site-specific manner in bottom-up-synthesized NCPs. Detailed mechanistic studies on these NCPs revealed that histones actively participate in DNA damage and repair processes in diverse ways. For instance, nucleophilic residues in the flexible histone N-terminal tails, such as Lys and N-terminal α-amine, react with electrophilic DNA damage and reactive intermediates. In some cases, transient intermediates are produced, leading to the promotion or suppression of damage and repair processes. In other examples, reactions with histones yield reversible or stable DNA-protein cross-links (DPCs). Histones also utilize acidic and basic residues, such as histidine and aspartic acid, to catalyze DNA strand cleavage through general acid/base catalysis. Alternatively, a Tyr in histone plays a vital role in nucleosomal DNA damage and repair via radical transfer. Finally, the reactivity discovered during the mechanistic studies has facilitated the development of new reagents and methods with applications in biotechnology.This research has enriched our knowledge of the roles of histone proteins in DNA damage and repair and their contributions to epigenetics and may have significant biological implications. The residues in histone N-terminal tails that react with DNA lesions also play pivotal roles in regulating the structure and function of chromatin, indicating that there may be cross-talk between DNA damage and repair in eukaryotic cells and epigenetic regulation. Also, in view of the biased amino acid composition of histones, these results provide hints about how the proteins have evolved to minimize their deleterious effects but maximize beneficial ones for maintaining genome integrity. Finally, previously unreported DPCs and histone post-translational modifications have been discovered through this research. The effects of these newly identified lesions on the structure and function of chromatin and their fates inside cells remain to be elucidated.

Roles of Histone Deacetylases in Acute Myeloid Leukemia With Fusion Proteins

Accurate orchestration of gene expression is critical for the process of normal hematopoiesis, and dysregulation is closely associated with leukemogenesis. Epigenetic aberration is one of the major causes contributing to acute myeloid leukemia (AML), where chromosomal rearrangements are frequently found. Increasing evidences have shown the pivotal roles of histone deacetylases (HDACs) in chromatin remodeling, which are involved in stemness maintenance, cell fate determination, proliferation and differentiation, via mastering the transcriptional switch of key genes. In abnormal, these functions can be bloomed to elicit carcinogenesis. Presently, HDAC family members are appealing targets for drug exploration, many of which have been deployed to the AML treatment. As the majority of AML events are associated with chromosomal translocation resulting in oncogenic fusion proteins, it is valuable to comprehensively understand the mutual interactions between HDACs and oncogenic proteins. Therefore, we reviewed the process of leukemogenesis and roles of HDAC members acting in this progress, providing an insight for the target anchoring, investigation of hyperacetylated-agents, and how the current knowledge could be applied in AML treatment.