DNA Methyltransferase Activity Research Articles

Botulinum toxin type A prevents the phenotypic transformation of fibroblasts induced by TGF‑β1 via the PTEN/PI3K/Akt signaling pathway.

Hypertrophic scar (HS) is a common type of dermatosis. Botulinum toxin type A (BTXA) can exert an anti-HS effect; however, the regulatory mechanisms underlying this effect remain unclear. Thus, the aim of this study was to examine the effects of BTXA on phosphatase and tensin homolog deleted on chromosome ten (PTEN) expression and the fibroblast phenotypic transformation induced by transforming growth factor (TGF)-β1, which is an important regulatory factor involved in the process of HS. For this purpose, fibroblasts were treated with various concentrations of BTXA and then treated with 10 ng/ml of TGF-β1 with gradient concentrations of BTXA. The proliferation and apoptosis of fibroblasts were measured by cell counting kit-8 assay (CCK-8) and flow cytometry, respectively. PTEN methylation was analyzed by methylation-specific PCR (MSP) and DNA methyltransferase (DNMT) activity was determined using a corresponding kit. RT-qPCR and western blot analysis were performed to detect the transcription and translation levels. The results revealed that BTXA suppressed the proliferation and increased the apoptosis of fibroblasts treated with TGF-β1 in a dose-dependent manner. BTXA in combination with TGF-β1 suppressed the expression of molecules related to the extracellular matrix (ECM), epithelial-mesenchymal transition (EMT) and apoptosis. BTXA reduced the PTEN methylation level and downregulated the expression levels of methylation-associated genes. BTXA also inhibited the phosphorylation of phosphoinositide 3-kinase (PI3K) and Akt. On the whole, the findings of this study indicate that BTXA may inhibit fibroblast phenotypic transformation by regulating PTEN methylation and the phosphorylation of related pathways. The findings of this study can provide a theoretical basis for HS treatment.

DNA methylation and regulation of DNA methyltransferases in a freeze-tolerant vertebrate.

The wood frog is one of the few freeze-tolerance vertebrates. This is accomplished in part by the accumulation of cryoprotectant glucose, metabolic rate depression, and stress response activation. These may be achieved by mechanisms such as DNA methylation, which is typically associated with transcriptional repression. Hyperglycemia is also associated with modifications to epigenetic profiles, indicating an additional role that the high levels of glucose play in freeze tolerance. We sought to determine whether DNA methylation is affected during freezing exposure, and whether this is due to the wood frog's response to hyperglycemia. We examined global DNA methylation and DNA methyltransferases (DNMTs) in the liver and muscle of frozen and glucose-loaded wood frogs. The results showed that levels of 5-methylcytosine (5mC) increased in the muscle, suggesting elevated DNA methylation during freezing. DNMT activities also decreased in muscle during thawing, glucose loading, and in vitro glucose experiments. Liver DNMT activities were similar to muscle; however, a varied response to DNMT levels and a decrease in 5mC highlight the metabolic role the liver plays during freezing. Glucose was also shown to decrease DNMT activity levels in the wood frog, in vitro, elucidating a potentially novel regulatory mechanism. Together these results suggest an interplay between freeze tolerance and hyperglycemic regulation of DNA methylation.

SALL3 expression balance underlies lineage biases in human induced pluripotent stem cell differentiation

Clinical applications of human induced pluripotent stem cells (hiPSCs) are expected, but hiPSC lines vary in their differentiation propensity. For efficient selection of hiPSC lines suitable for differentiation into desired cell lineages, here we identify SALL3 as a marker to predict differentiation propensity. SALL3 expression in hiPSCs correlates positively with ectoderm differentiation capacity and negatively with mesoderm/endoderm differentiation capacity. Without affecting self-renewal of hiPSCs, SALL3 knockdown inhibits ectoderm differentiation and conversely enhances mesodermal/endodermal differentiation. Similarly, loss- and gain-of-function studies reveal that SALL3 inversely regulates the differentiation of hiPSCs into cardiomyocytes and neural cells. Mechanistically, SALL3 modulates DNMT3B function and DNA methyltransferase activity, and influences gene body methylation of Wnt signaling-related genes in hiPSCs. These findings suggest that SALL3 switches the differentiation propensity of hiPSCs toward distinct cell lineages by changing the epigenetic profile and serves as a marker for evaluating the hiPSC differentiation propensity.

Effect of Disease-Associated Germline Mutations on Structure Function Relationship of DNA Methyltransferases.

Despite a large body of evidence supporting the role of aberrant DNA methylation in etiology of several human diseases, the fundamental mechanisms that regulate the activity of mammalian DNA methyltransferases (DNMTs) are not fully understood. Recent advances in whole genome association studies have helped identify mutations and genetic alterations of DNMTs in various diseases that have a potential to affect the biological function and activity of these enzymes. Several of these mutations are germline-transmitted and associated with a number of hereditary disorders, which are potentially caused by aberrant DNA methylation patterns in the regulatory compartments of the genome. These hereditary disorders usually cause neurological dysfunction, growth defects, and inherited cancers. Biochemical and biological characterization of DNMT variants can reveal the molecular mechanism of these enzymes and give insights on their specific functions. In this review, we introduce roles and regulation of DNA methylation and DNMTs. We discuss DNMT mutations that are associated with rare diseases, the characterized effects of these mutations on enzyme activity and provide insights on their potential effects based on the known crystal structure of these proteins.

Detection of epigenetic effects of citrinin using a yeast-based bioassay.

The present study investigated the effects of citrinin (CIT) on a yeast-transformed human DNA methyltransferase (DNMT) associated with flocculation that can be inhibited by epigenetic mutagens. CIT (0.5-2μmol/L) inhibited the flocculation levels of yeast transfected with DNMT-genes (DNMT yeast) and the reporter gene activity of FLO1, which has been associated with flocculation. In contrast, the same concentrations of CIT had little effect on reporter activity under the control of a less methylation-sensitive FLO1 promoter. It was also shown that bacterial DNMT activity could be inhibited in the presence of CIT (4 and 40μmol/L). These results show that CIT has inhibitory activity of DNMT, suggesting that the cytotoxicity of CIT may be involved in epigenetic mutagenicity.

Chromatin architecture and DNA methylation-associated epigenetic changes in ethephon-primed sprouts of soybean [Glycine max (L.) Merrill

The simplest structure phytohormone ethylene (C2H4) regulates the important aspect of plant growth and development throughout its life cycle. So far, no systemic studies were performed to determine the ethylene effect on seed germination-associated epigenetic phenomenon. Henceforth, a laboratory investigation was performed to explore the epigenetic impact of ethephon (ET) priming on soybean [Glycine max (L.) Merrill] germination. Our findings demonstrated that ET (250 ppm) induced soybean germination significantly: (1) altered the chromatin architecture; (2) reduced the global DNA methylation and 5-methylcytosine levels; (3) reduced the DNA methyltransferases (DNMTs) activity; (4) decreased and increased the transcript levels of DNA methylases (viz. GmMET1, GmDRM1 and GmCMT3) and demethylase (viz. GmROS1), respectively; and (5) enhanced the endogenous levels of DNMT inhibitor, genistein. Based on these observations, a novel epigenetic impact of ethylene in seed germination process has been proposed.

A DNMT3A PWWP mutation leads to methylation of bivalent chromatin and growth retardation in mice

DNA methyltransferases (DNMTs) deposit DNA methylation, which regulates gene expression and is essential for mammalian development. Histone post-translational modifications modulate the recruitment and activity of DNMTs. The PWWP domains of DNMT3A and DNMT3B are posited to interact with histone 3 lysine 36 trimethylation (H3K36me3); however, the functionality of this interaction for DNMT3A remains untested in vivo. Here we present a mouse model carrying a D329A point mutation in the DNMT3A PWWP domain. The mutation causes dominant postnatal growth retardation. At the molecular level, it results in progressive DNA hypermethylation across domains marked by H3K27me3 and bivalent chromatin, and de-repression of developmental regulatory genes in adult hypothalamus. Evaluation of non-CpG methylation, a marker of de novo methylation, further demonstrates the altered recruitment and activity of DNMT3AD329A at bivalent domains. This work provides key molecular insights into the function of the DNMT3A-PWWP domain and role of DNMT3A in regulating postnatal growth.

160 Mechanisms governing promoter methylation and apoptosis in cutaneous T-cell lymphoma: implications for therapy with methotrexate and JAK-inhibitors

Cutaneous T-cell lymphoma (CTCL) is characterized by resistance to apoptosis involving dysregulation of the FAS ligand (FASL) - FAS death receptor pathway. CTCL cells also exhibit constitutively activated STAT proteins, which are known to upregulate and bind DNA methyltransferases (DNMTs). We hypothesized that, like many other tumor suppressor genes, FAS and FASL expression is at least partially regulated by promoter methylation. Earlier, we showed that methotrexate (MTX), a known folate antagonist, acts as a DNA methylation inhibitor via depleting the methyl donor, S-adenosylmethionine (SAM), in CTCL cells. Pyrosequencing analysis of FAS and FASL promoters showed that MTX inhibited methylation of certain CpG sites in these genes, which resulted in increased FAS/FASL expression and subsequent apoptosis via activated caspase 8. We found that shRNA mediated genetic knockdown of DNMT -1 and -3A also resulted in upregulation of FASL mRNA and protein in CTCL cell lines. However, the reduction in FASL promoter methylation induced by MTX was generally superior to that induced by shRNA knockdown and was not improved by a combination of MTX plus knockdown. Because STAT proteins help regulate DNMTs, we also evaluated the effect of multiple JAK inhibitors (fedratinib, tofacitinib, and ruxolitinib) in CTCL cells and Sezary patient’s blood. Among these, fedratinib treatment was most effective in decreasing viability, spheroid formation, and inducing apoptosis. These responses were accompanied by decreased phosphorylation of STAT3 at tyrosine-705. Taken together, our data demonstrate that enhanced apoptosis of CTCL can be induced by MTX, DNMT knockdown and JAK inhibitors. This is consistent with a mechanistic cascade in which activated STATs enhance DNMT activities that in turn suppress the expression of apoptotic factors and promote CTCL survival. Our findings suggest a therapeutic role for MTX and JAK inhibitors in the management of CTCL.

Spermine and gene methylation: a mechanism of lifespan extension induced by polyamine-rich diet.

The polyamines spermidine and spermine are synthesized in almost all organisms and are also contained in food. Polyamine synthesis decreases with aging, but no significant decrease in polyamine concentrations were found in organs, tissues, and blood of adult animals and humans. We found that healthy dietary patterns were associated with a preference for polyamine-rich foods, and first reported that increased polyamine intake extended the lifespan of mice and decreased the incidence of colon cancer induced by repeated administration of moderate amounts of a carcinogen. Recent investigations have revealed that changes in DNA methylation status play an important role in lifespan and aging-associated pathologies. The methylation of DNA is regulated by DNA methyltransferases in the presence of S-adenosylmethionine. Decarboxylated S-adenosylmethionine, converted from S-adenosylmethionine by S-adenosylmethionine decarboxylase, provides an aminopropyl group to synthesize spermine and spermidine and acts to inhibit DNMT activity. Long-term increased polyamine intake were shown to elevate blood spermine levels in mice and humans. In vitro studies demonstrated that spermine reversed changes induced by the inhibition of ornithine decarboxylase (e.g., increased decarboxylated S-adenosylmethionine, decreased DNA methyltransferase activity, increased aberrant DNA methylation), whose activity decreases with aging. Further, aged mice fed high-polyamine chow demonstrated suppression of aberrant DNA methylation and a consequent increase in protein levels of lymphocyte function-associated antigen 1, which plays a pivotal role on inflammatory process. This review discusses the relation between polyamine metabolism and DNA methylation, as well as the biological mechanism of lifespan extension induced by increased polyamine intake.

Terminal Deoxynucleotidyl Transferase and Rolling Circle Amplification Induced G-triplex Formation: A Label-free Fluorescent Strategy for DNA Methyltransferase Activity Assay

It is of great significance to sensitively detect DNA methyltransferase (MTase) activity and screen its inhibitory drugs in the field of human cancer diagnosis and disease therapeutics. In this work, based on terminal deoxynucleotidyl transferase (TdT)-induced rolling circle amplification (RCA), we construct a label-free and highly sensitive fluorescence biosensing strategy for DNA MTase activity analysis. The hairpin substrate is methylated by Dam MTase and cleaved by Dpnl to generate a DNA fragment with a free 3′-hydroxy (3′−OH) terminus that is extended by TdT to obtain a long adenine (poly-A) tail. Subsequently, the resulting poly-A work as primer triggers RCA reaction and generate lots of G-triplexes which can combine with Thioflavin T (ThT) to achieve the apparent fluorescence signal. Integrate TdT-induced RCA with G-triplex@ThT, Dam MTase can be detected down to 0.058 U/mL with a wide linear range from 0.1 U/mL to 40 U/mL. In addition, the method exhibits high selectivity to other MTases. We also successfully demonstrate this work can be used in complex matrixes assay and screen MTase inhibitors. Thus, in the area of DNA MTase-related cancer diagnosis and disease therapeutics, the developed method may be a promising tool for the detection of Dam MTase.

A Photo‐responsive Small‐Molecule Approach for the Opto‐epigenetic Modulation of DNA Methylation

AbstractControlling the functional dynamics of DNA within living cells is essential in biomedical research. Epigenetic modifications such as DNA methylation play a key role in this endeavour. DNA methylation can be controlled by genetic means. Yet there are few chemical tools available for the spatial and temporal modulation of this modification. Herein, we present a small‐molecule approach to modulate DNA methylation with light. The strategy uses a photo‐tuneable version of a clinically used drug (5‐aza‐2′‐deoxycytidine) to alter the catalytic activity of DNA methyltransferases, the enzymes that methylate DNA. After uptake by cells, the photo‐regulated molecule can be light‐controlled to reduce genome‐wide DNA methylation levels in proliferating cells. The chemical tool complements genetic, biochemical, and pharmacological approaches to study the role of DNA methylation in biology and medicine.

A Photo-responsive Small-Molecule Approach for the Opto-epigenetic Modulation of DNA Methylation.

Controlling the functional dynamics of DNA within living cells is essential in biomedical research. Epigenetic modifications such as DNA methylation play a key role in this endeavour. DNA methylation can be controlled by genetic means. Yet there are few chemical tools available for the spatial and temporal modulation of this modification. Herein, we present a small‐molecule approach to modulate DNA methylation with light. The strategy uses a photo‐tuneable version of a clinically used drug (5‐aza‐2′‐deoxycytidine) to alter the catalytic activity of DNA methyltransferases, the enzymes that methylate DNA. After uptake by cells, the photo‐regulated molecule can be light‐controlled to reduce genome‐wide DNA methylation levels in proliferating cells. The chemical tool complements genetic, biochemical, and pharmacological approaches to study the role of DNA methylation in biology and medicine.

Epigenetic silencing of genes enhanced by collective role of reactive oxygen species and MAPK signaling downstream ERK/Snail axis: Ectopic application of hydrogen peroxide repress CDH1 gene by enhanced DNA methyltransferase activity in human breast cancer

Loss of E-cadherin and epithelial to mesenchymal transition (EMT) are key steps in cancer progression. Reactive oxygen species (ROS) play significant roles in cellular physiology and homeostasis. Roles of E-cadherin (CDH1), EMT and ROS are intriguingly illustrated in many cancers without focusing their collective concert during cancer progression. We report that hydrogen peroxide (H2O2) treatment modulate CDH1 gene expression by epigenetic modification(s). Sublethal dosage of H2O2 treatment decrease E-cadherin, increase DNMT1, HDAC1, Snail, Slug and enrich H3K9me3 and H3K27me3 in the CDH1 promoter. The effect of H2O2 was attenuated by ROS scavengers; NAC, lupeol and beta-sitosterol. DNMT inhibitor, AZA prevented the H2O2 induced promoter-CpG-island methylation of CDH1. Treatment of cells with U0126 (inhibitor of ERK) reduced the expression of DNMT1, Snail and Slug, increased CDH1. This implicates that CDH1 is synergistically repressed by histone methylation, DNA methylation and histone deacetylation mediated chromatin remodelling and activation of Snail and Slug through ERK pathway. Increased ROS leads to activation of epigenetic machineries and EMT activators Snail/Slug which in their course of action inactivates CDH1 gene and lack of E-cadherin protein promotes EMT in breast cancer cells. ROS and ERK signaling facilitate epigenetic silencing and support the fact that subtle increase of ROS above basal level act as key cell signaling molecules. Free radical scavengers, lupeol and beta-sitosterol may be tested for therapeutic intervention of breast cancer. This work broadens the amplitude of epigenome and open avenues for investigations on conjoint effects of canonical and intrinsic metabolite signaling and epigenetic modulations in cancer.

A dual-response biosensor for electrochemical and glucometer detection of DNA methyltransferase activity based on functionalized metal-organic framework amplification

DNA methylation is catalyzed by DNA methyltransferase (MTase) and concerned with many biological processes including pathogenesis of various human diseases. The monitoring of MTase activity is thus of great significance in disease diagnosis and drug screening. Herein, we developed a facile way to synthesize biocompatible invertase enzyme modified metal-organic framework (Invertase/MOF) materials, and explored its application in constructing a dual-response Dam MTase sensor for the first time. By using them as signal probes, in which high density of metal sites could be electrochemically detected and invertase could hydrolyze sucrose into glucose for generation of glucometer signal output, dual-response for accurate detection of Dam MTase was realized. In the presence of Dam MTase, the methylation of hairpin probe 1 (HP1) occurred and thus caused the cleavage of HP1 assisted by a restriction endonuclease (DpnI) to produce the binding sequences. The binding sequences then hybridized with the electrode-assembled HP2 to expose their sticky termini which sequentially hybridized with the Invertase/MOFs-tethered capture probes. Finally, the electrodes were incubated with a sucrose solution, followed by the separate electrochemical and glucometer detection. The present assay brought good performance which could detect Dam MTase activity as low as 0.001 U mL−1 with wide linear range and good selectivity against other cytosine MTase (M.SssI MTase). Moreover, it also owns ability to be potentially applied for the inhibitors screening by utilization of 5-fluorouracil as an inhibitor model. The results imply that our proposed method provides a convenient platform for early cancer diagnosis and therapeutic applications.

A requirement for epigenetic modifications during noradrenergic stabilization of heterosynaptic LTP in the hippocampus.

Beta-adrenergic receptor (b-AR) activation by noradrenaline (NA) enhances memory formation and long-term potentiation (LTP), a form of synaptic plasticity characterized by an activity-dependent increase in synaptic strength. LTP is believed to be a cellular mechanism for contextual learning and memory. In the mammalian hippocampus, LTP can be observed at multiple synaptic pathways after strong stimulation of a single synaptic pathway. This heterosynaptic LTP is believed to involve synaptic tagging of active synapses and capture of plasticity-related proteins that enable heterosynaptic transfer of persistent potentiation. These processes may permit distinct neural pathways to associate information transmitted by separate, but convergent, synaptic inputs. We had previously shown that transcription and epigenetic modifications were necessary for stabilization of homosynaptic LTP. However, it is unclear whether transfer of LTP to a second, heterosynaptic pathway involves b-ARs signalling to the nucleus. Using electrophysiologic recordings in area CA1 of murine hippocampal slices, we show here that pharmacologically inhibiting b-AR activation, transcription, DNA methyltransferase or histone acetyltransferase activation, prevents stabilization of heterosynaptic LTP. Our data suggest that noradrenergic stabilization of heterosynaptic ("tagged") LTP requires not only transcription, but specifically, DNA methylation and histone acetylation. NA promotes stable heterosynaptic plasticity through engagement of nuclear processes that may contribute to prompt consolidation of short-term memories into resilient long-term memories under conditions when the brain's noradrenergic system is recruited.

MIR29B mediates epigenetic mechanisms of HBG gene activation.

SummarySickle cell disease (SCD) affects over 2 million people worldwide with high morbidity and mortality in underdeveloped countries. Therapeutic interventions aimed at reactivating fetal haemoglobin (HbF) is an effective approach for improving survival and ameliorating the clinical severity of SCD. A class of agents that inhibit DNA methyltransferase (DNMT) activity show promise as HbF inducers because off‐target effects are not observed at low concentrations. However, these compounds are rapidly degraded by cytidine deaminase when taken by oral administration, creating a critical barrier to clinical development for SCD. We previously demonstrated that microRNA29B (MIR29B) inhibits de novo DNMT synthesis, therefore, the goal of our study was to determine if MIR29 mediates HbF induction. Overexpression of MIR29B in human KU812 cells and primary erythroid progenitors significantly increased the percentage of HbF positive cells, while decreasing the expression of DNMT3A and the HBG repressor MYB. Furthermore, HBG promoter methylation levels decreased significantly following MIR29B overexpression in human erythroid progenitors. We subsequently, observed higher MIR29B expression in SCD patients with higher HbF levels compared to those with low HbF. Our findings provide evidence for the ability of MIR29B to induce HbF and supports further investigation to expand treatment options for SCD.

Inhibitory effect of ochratoxin A on DNMT-mediated flocculation of yeast.

The mycotoxin ochratoxin A (OTA) is considered to be a human carcinogen. However, the mode of its carcinogenetic action has not been elucidated. Recently, it has become evident that epigenetic changes influence the risk of developing cancer. Since it has been revealed that the yeast flocculation displayed by the strains transformed with human DNA methyltransferases (DNMT) can be regulated by epigenetic mechanisms, we examined the effect of OTA on the transcription level of FLO1, which mediates the flocculation phenotype. OTA but not a non-carcinogenetic mycotoxin deoxynivalenol (DON) inhibited the intensity of GFP fluorescence under the transcriptional regulation of FLO1 promoter in a dose-dependent manner. At the same time, OTA had no effect on the reporter activity under the control of modified FLO1 promoter with reduced CpG motifs. In addition, it was confirmed that the flocculation and FLO1 mRNA of DNMT gene-transformed yeast (DNMT yeast) were decreased by OTA. In vitro methylation assay using a bacterial DNMT revealed an inhibitory effect of OTA on the DNMT activity, and OTA treatment reduced the frequency of abnormally shaped nuclei which were often observed in DNMT yeast. These results suggest that the carcinogenicity of OTA may involve inhibition of DNMT-mediated epigenetic regulation.

A study on alterations in mitochondrial biological characteristics during cellular senescence of human embryonic lung fibroblasts

Objective: To study the alterations of mitochondrial biological characteristics during both cellular replicative and premature senescence induced by hydrogen peroxide in human embryonic lung fibroblasts (HEFs). Methods: The premature senescence was induced by 400 μmol/L H(2)O(2) once a day at the same time and with 2 hours each time, after four consecutive days the premature senescence models were classified into premature senescence initiation group (PSi) and premature senescence persistence group (PSp). Based on the life span of HEFs, the cell replicative senescence was divided into five groups included young-age (22 PDL), middle-age (35 PDL), replicative senescence (49 PDL), PSi and PSp. The mitochondrial distribution, relative content, adenosine triphosphate (ATP) contents, 8-hydroxydeoxyguanosine (8-OHdG) levels, the relative mitochondrial transcription factor A (TFAM) as well as mitochondrial DNA methyltransferase 1 (mtDNMT1) mRNA levels, mtDNA copy number, the relative TFAM protein level and the total enzyme activity of mitochondrial DNA methyltransferases (mtDNMTs) were detected in five senescence groups. Results: The mtDNA copy number, 8-OHdG contents, level of mtDNMT1 mRNA and mtDNMTs activity in 49 PDL group were higher than those in 22 PDL group (all P values <0.05); The level of 8-OHdG in PSi was higher than that in 22 PDL group (P<0.05); The ATP contents, mtDNA copy number, the mRNA and protein expression levels of TFAM and mtDNMTs activity of PSp were higher than those in 22 PDL group (all P values<0.05). Conclusion: During the cellular senescence of HEFs, the higher mtDNA copy number and mtDNMTs activity were common features regardless of replicative or premature senescence, with possibility that oxidative stress was involved in modifying the occurrence of premature senescence.

The role of DNA methyltransferase activity in cocaine treatment and withdrawal in the nucleus accumbens of mice.

An increasing number of reports have provided crucial evidence that epigenetic modifications, such as DNA methylation, may be involved in initiating and establishing psychostimulant-induced stable changes at the cellular level by coordinating the expression of gene networks, which then manifests as long-term behavioral changes. In this study, we evaluated the enzyme activity of DNA methyltransferases (DNMTs) after cocaine treatment and during withdrawal. Furthermore, we studied how genetic or pharmacological inhibition of DNMTs in mouse nucleus accumbens (NAc) affects the induction and expression of cocaine-induced behavioral sensitization. Our results showed that after silencing Dnmt3a in the NAc during the induction phase of cocaine-induced sensitization, overall DNMT activity decreases, correlating negatively with behavioral sensitization. Reduced Dnmt3a mRNA during this phase was the largest contributing factor for decreased DNMT activity. Cocaine withdrawal and a challenge dose increased DNMT activity in the NAc, which was associated with the expression of behavioral sensitization. Long-term selective Dnmt3a transcription silencing in the NAc did not alter DNMT activity or the expression of cocaine-induced behavioral sensitization. However, bilateral intra-NAc injection of a non-specific inhibitor of DNMT (RG108) during withdrawal from cocaine decreased DNMT activity in the NAc and had a small effect on the expression of cocaine-induced behavioral sensitization. Thus, cocaine treatment and withdrawal is associated with biphasic changes in DNMT activity in the NAc, and the expression of behavioral sensitization decreases with non-selective inhibition of DNMT but not with selective silencing of Dnmt3a.

Dual-Amplification Strategy-Based SERS Chip for Sensitive and Reproducible Detection of DNA Methyltransferase Activity in Human Serum.

Herein, we present a dual-amplification sensing strategy-based surface-enhanced Raman scattering (SERS) chip, which combines rolling circle amplification (RCA) and polyadenine (PolyA) assembly for sensitive and reproducible determination of the activity of M.SssI, a cytosine-guanine dinucleotide (CpG) methyltransferase (MTase). Typically, in the presence of M.SssI, RCA process is triggered, resulting in long, single-stranded DNA (ssDNA) fragments that are hybridized with thousands of Raman reporters of Cy3. Afterward, the resultant ssDNA fragments are conjugated to SERS-active substrates made of silver core-gold satellite nanocomposites-modified silicon wafer (Ag-Au NPs@Si), with the SERS enhancement factor of ∼5 × 106. The core-satellite nanostructures are assembled relied on the strong affinity of PolyA toward gold/silver surface. Of particular significance, the developed SERS chip displays an ultrahigh sensitivity with a low limit of detection (LOD) of 2.8 × 10-3 U/mL, which is around 2 orders of magnitude higher than most reported methods. In addition, the constructed chip features a broad detection range covering from 0.05 to 50 U/mL. Besides for the ultrahigh sensitivity and broad dynamic range, the chip also features good reproducibility (e.g., the relative standard deviation (RSD) is less than ∼12%). Taking advantages of these merits, the developed chip is feasible for accurate discrimination of M.SssI with various concentrations spiked in human serum samples with good recoveries ranging from 99.6% to 107%.