Flavonoidal alkaloids from the flowers of Chromolaena odorata (L.) R.M.King & H.Rob.

A pair of epimers of flavonoid alkaloids, with a pyrrolidone moiety, 2S,5''R-eupodoratin A (1), 2S,5''S-eupodoratin A (2), together with two known analogues, drahebephin A (3), drahebephin B (4), were isolated from the flowers of Chromolaena odorata (L.) R.M.King & H.Rob. Their structures were elucidated on the basis of HR-ESI-MS, 1D/2D NMR spectral analyses. The absolute configuration of compounds (1) and (2) was determined by its experimental and calculated electronic circular dichroism (ECD) spectra. All compounds were isolated from the Asteraceae family for the first time. The ABTS·+ scavenging activity of compound (4) reached 93.56% at a concentration of 0.5 mM, while the scavenging capacity of positive control Trolox was 55.94%. In addition, all compounds show moderate antimicrobial activity against Escherichia coli (ATCC, 337304), Staphylococcus aureus (ATCC, 337371) and Candida albicans (ATCC, 186382) with a MIC value of more than 50 µg/mL.

[Effect of fire needling on imiquimod induced psoriasis-like lesion and STAT3 pathway in mice].

OBJECTIVE: To observe the effect of fire needling on psoriasis-like lesion and the signal transducer and activator of transcription 3 (STAT3) pathway in mice and compare the therapeutic effect between different interventions of fire needling therapy (surrounding technique of fire needling, fire needling at "Dazhui" [GV 14] and "Zusanli" [ST 36]). METHODS: Thirty male BALB/c mice were randomized into a blank group, a model group, a dexamthasone group, a surrounding technique group and an acupoint group, 6 mice in each one. Except the blank group, the mice in the rest groups were established as psoriasis-like lesion model by topical application with imiquimod cream, once daily, consecutively for 8 days. From day 4 to day 8, in the dexamthasone group, gastric infusion with 0.2 mL dexamthasone was administered, once daily. On day 4, 6 and 8, in the surrounding technique group, fire needling was exerted around the skin lesion; and fire needling was applied to "Dazhui" (GV 14) and "Zusanli" (ST 36) in the acupoint group, once a day. The changes in skin lesion on the dorsal parts of mice were observed in each group to score the psoriasis area and severity index (PASI). Using HE staining, the dermal morphological changes and epidermal thickness were observed in the mice of each group. The positive expression of proliferating cell-associated antigen Ki-67 was determined by immunofluorescence. Immunohistochemistry method was used to determine the expressions of , and T cells of skin tissue in each group. Using real-time PCR, the expressions of interleukin (IL)-17, IL-22, tumor necrosis factor α(TNF-α) mRNA were determined. Western blot method was adopted to determine the protein expressions of STAT3 and p-STAT3 in skin tissue in each group. RESULTS: Compared with the blank group, the scores of each item and the total scores of PASI, as well as the epidermal thickness were all increased in the mice of the model group (P<0.01). Except for the erythema scores of the dexamethasone group and the surrounding technique group, the scores of each item and the total scores of PASI, as well as the epidermal thickness were all decreased in each intervention group as compared with the model group (P<0.01). The infiltration scores and the total scores in the dexamethasone group and the acupoint group were lower than those in the surrounding technique group respectively (P<0.01, P<0.05). In comparison with the blank group, Ki-67 positive cell numbers and the numbers of , and T cells in skin tissue were increased in the mice of the model group (P<0.01). Ki-67 positive cell numbers and the numbers of , and T cells were reduced in each intervention group as compared with the model group (P<0.01), and the numbers of and T cells in the acupoint group were less than the surrounding technique group (P<0.01). Compared with the blank group, the mRNA expressions of IL-17, IL-22 and TNF-α and the ratio of p-STAT3 to STAT3 were all increased in the model group (P<0.01). The mRNA expressions of IL-17, IL-22 and TNF-α and the ratio of p-STAT3 to STAT3 were all decreased in each intervention group as compared with the model group (P<0.01, P<0.05). The mRNA expressions of IL-17, IL-22 and TNF-α in the acupoint group, as well as mRNA expression of IL-17 in the surrounding technique group were all lower than the dexamethasone group (P<0.01), while, the mRNA expression of IL-22 in the acupoint group was lower than the surrounding technique group (P<0.01). CONCLUSION: Fire needling therapy improves skin lesion severity in imiquimod induced psoriasis-like lesion of the mice, which is probably related to the inhibition of STAT3 pathway activation and the decrease of Th17 inflammatory factors expression. The systemic regulation of fire needling at "Dazhui" (GV 14) and "Zusanli" (ST 36) is superior to the local treatment.

Self-Reinforced Cancer Targeting (SRCT) Depending on Reciprocally Enhancing Feedback between Targeting and Therapy.

Conventional cancer targeting methodology needs to be reformed to overcome the intrinsic barriers responsible for poor targeting efficiency. This study describes a concept of self-reinforced cancer targeting (SRCT) by correlating targeting with therapy in a reciprocally enhancing manner. SRCT is achieved on the basis of two prerequisites: (1) target molecules have to be expressed on cancer cell membranes but not on normal cells, and (2) notably, their expression on cancer cells must be actively upregulated in response to cellular attack by cancer treatments. As a proof-of-concept, a GRP78-targeting nanovehicle for chemotherapy was designed. Resultant data showed that chemotherapeutic drugs could effectively elevate GRP78 expression on the plasma membranes of cancer cells while having minimal influence on normal cells. DOX pretreatment of cancer cells and tumor tissues can greatly increase the targeting efficacy and therapeutic performance of the prepared GRP78-targeting nanomedicine while somewhat disfavoring the nontargeting counterpart. In vivo and in vitro results demonstrated that this GRP78-targeting nanomedicine could accurately target cancer cells to not only implement chemotherapy but also induce GRP78 upregulation on cancer cells, eventually benefiting continuous cancer-cell-targeted attack by the nanomedicines remaining in the blood circulation or administered in the next dose. The GRP78-targeting nanomedicine displays much better antitumor performance compared with the nontargeting counterpart. SRCT is expected to advance cancer-targeted therapy based on the positive dependency between targeting and therapeutic modalities.

[Effect of moxibustion on skin lesions and immune inflammatory response in psoriasis mice].

OBJECTIVE: To observe the effect of moxibustion on skin lesions and immune inflammatory response in psoriasis mice, and to explore the possible mechanism of moxibustion for psoriasis. METHODS: A total of 32 male BALB/c mice were randomly divided into a normal group, a model group, a moxibustion group and a medication group, 8 mice in each group. Psoriasis model was induced by applying 5% imiquimod cream on the back for 7 days in the model group, the moxibustion group and the medication group. At the same time of model establishment, the moxibustion group was treated with suspension moxibustion on skin lesions on the back, 20 min each time, once a day; the medication group was treated with 1 mg/kg methotrexate tablet solution by gavage, once a day. Both groups were intervened for 7 days. The daily changes of skin lesions were observed, and the psoriasis area and severity index (PASI) score was evaluated; the histopathological changes of skin lesions were observed by HE staining; the positive expression of proliferating cell nuclear antigen (PCNA) and T lymphocyte surface marker CD3 were detected by immunohistochemistry; the expression level of serum interleukin (IL) -17A was detected by ELISA, and the relative expressions of tumor necrosis factor-α (TNF-α), IL-1ß and IL-6 mRNA in skin lesions were detected by real-time PCR. RESULTS: The increased and hypertrophy scale, dry skin, red and swollen epidermis and obvious infiltration were observed in the model group, and each score and total score of PASI were higher than those in the normal group (P<0.01). The scale score, infiltration score, and total score of PASI in the moxibustion group were lower than those in the model group (P<0.01); the infiltration score and total score of PASI in the medication group were lower than those in the model group (P<0.01, P<0.05). The inflammatory cell infiltration in the model group was obvious, and the thickness of epidermal layer was increased compared with that in the normal group (P<0.01); the inflammatory cell infiltration and Munro micro abscess were decreased in the moxibustion group and the medication group, and the thickness of epidermal layer was decreased compared with that in the model group (P<0.01). Compared with the normal group, the positive cell number of PCNA and T was increased (P<0.01), and the body mass was decreased, and the spleen index was increased (P<0.01), and the expression of serum IL-17A and the relative expression of TNF-α, IL-1ß and IL-6 mRNA in the skin lesions was increased in the model group (P<0.01). Compared with the model group, the positive cell number of PCNA and T was reduced (P<0.01), and the spleen index and the relative expression of TNF-α, IL-1ß and IL-6 mRNA were reduced (P<0.01) in the moxibustion group and the medication group; the body mass of mice in the moxibustion group was higher than that in the model group (P<0.01); the content of serum IL-17A in the medication group was lower than that in the model group (P<0.01); the relative expression of TNF-α, IL-1ß mRNA in the moxibustion group was higher than that in the medication group (P<0.01). CONCLUSION: Moxibustion could effectively improve the scale and infiltration of skin lesions in psoriasis mice. Its mechanism may be related to inhibiting inflammatory response and regulating immunity.

[Moxibustion on plaque psoriasis of blood stasis: a randomized controlled trial].

OBJECTIVE: To observe the short-term and long-term effects of moxibustion on plaque psoriasis of blood stasis, and to compare the curative effect between moxibustion and calcipotriol ointment. METHODS: A total of 80 patients with plaque psoriasis of blood stasis were randomly divided into an observation group (40 cases, 2 cases dropped off) and a control group (40 cases, 4 cases dropped off). Both groups were given routine medical vaseline topical emollient basic treatment. In the observation group, moxibustion was applied to ashi point (target skin lesions), Zusanli (ST 36), Xuehai (SP 10) and Qihai (CV 6) for 30 min each time, 3 times a week. The control group was treated with calcipotriol ointment (0.25 g each time, once in the morning and evening) on the target skin lesions. Both groups were treated for 8 weeks. The psoriasis area and severity index (PASI) score before and after treatment, main clinical symptoms of TCM score and dermatology life quality index (DLQI) score before and after treatment and 3 and 6 moths follow-up were observed in the two groups; the clinical efficacy after treatment was evaluated and the recurrence rates of the two groups were followed up for 3 and 6 months after treatment. RESULTS: After treatment, the PASI scores in the both groups were lower than before treatment (P<0.01). After treatment and 3 and 6 months follow-up, the main clinical symptoms of TCM scores and DLQI scores of the two groups were lower than those before treatment (P<0.05), and at 3 and 6 months follow-up, those in the observation group were lower than the control group (P<0.01). There was no statistically significant difference between the observation group and the control group in overall effective rate and target skin lesion effective rate (P>0.05). At 3 and 6 months follow-up, the overall recurrence rate and target skin lesion recurrence rate in the observation group were lower than those in the control group (P<0.05). CONCLUSION: Both moxibustion and calcipotriol ointment have good short-term effects on plaque psoriasis of blood stasis. Moxibustion has more advantages in reducing the recurrence rate of psoriasis, improving the main clinical symptoms of TCM and quality of life.

Identification and characterization of two novel melanocortin-3 receptor mutations in Chinese obese individuals.

The melanocortin-3 receptor (MC3R) and melanocortin-4 receptor (MC4R), known as neural melanocortin receptors, have been implicated to be critical components of the hypothalamic leptin-melanocortin pathway and related to obesity pathogenesis. In contrast to extensive evidence from physiologic, biological, genetic studies demonstrating that MC4R is a critical regulator in obesity, whether MC3R mutation causes obesity is still controversial. In the present study, we screened for coding variants in the MC3R gene of 176 obese individuals (mean BMI 34.84 ± 0.19 kg/m2) and 170 lean controls (mean BMI 20.70 ± 0.08 kg/m2) to assess the prevalence of MC3R mutations in a Chinese cohort. Two novel mutations, A33D (c.C98 > A) and A259T (c.G775 > A), were identified in two subjects with morbid obesity, respectively. A259T was also identified in the carrier's sibling. In vitro functional studies showed that A33D was defective in the cAMP signaling pathway, whereas A259T MC3R had defective maximal binding and cAMP generation in response to NDP- and α-MSH, likely due to decreased cell surface expression. In addition, we showed that A33D and A259T were biased receptors and defect in constitutive activation of ERK1/2 signaling through MC3R might be a cause for morbid obesity. Our sequencing and co-segregation studies combined with comprehensive functional analysis demonstrated that A259T might be predisposing to obesity. Further investigations in larger cohorts will be needed in order to define this association and the specific phenotypic characteristics resulting from these mutations.

A MSN-based tumor-targeted nanoplatform to interfere with lactate metabolism to induce tumor cell acidosis for tumor suppression and anti-metastasis.

Lactate, the main contributor to the acidic tumor microenvironment, not only promotes the proliferation of tumor cells, but also closely relates to tumor invasion and metastasis. Here, a tumor targeting nanoplatform, designated as Me&Flu@MSN@MnO2-FA, was fabricated for effective tumor suppression and anti-metastasis by interfering with lactate metabolism of tumor cells. Metformin (Me) and fluvastatin sodium (Flu) were incorporated into MnO2-coated mesoporous silicon nanoparticles (MSNs), the synergism between Me and Flu can modulate the pyruvate metabolic pathway to produce more lactate, and concurrently inhibit lactate efflux to induce intracellular acidosis to kill tumor cells. As a result of the restricted lactate efflux, the extracellular lactate concentration is reduced, and the ability of the tumor cells to migrate is also weakened. This ingenious strategy based on Me&Flu@MSN@MnO2-FA showed an obvious inhibitory effect on tumor growth and resistance to metastasis.

Remodeling extracellular matrix based on functional covalent organic framework to enhance tumor photodynamic therapy.

Photodynamic therapy (PDT) is a promising treatment modality for tumor suppression. However, the hypoxic state of most solid tumors might largely hinder the efficacy of PDT. Here, a functional covalent organic framework (COF) is fabricated to enhance PDT efficacy by remodeling the tumor extracellular matrix (ECM). Anti-fibrotic drug pirfenidone (PFD) is loaded in an imine-based COF (COFTTA-DHTA) and followed by the decoration of poly(lactic-co-glycolic-acid)-poly(ethylene glycol) (PLGA-PEG) to fabricate PFD@COFTTA-DHTA@PLGA-PEG, or PCPP. After injected intravenously, PCPP can accumulate and release PFD in tumor sites, leading to down-regulation of ECM compenents such as hyaluronic acid (HA) and collagen I. Such depletion of tumor ECM reduces the intratumoral solid stress, a compressive force exerted by the ECM and cells, decompresses tumor blood vessels, and increases the density of effective vascular areas, resulting in significantly improved oxygen supply in tumor. Furthermore, PCPP-mediated tumor ECM depletion also enhances the tumor uptake of subsequently injected Protoporphyrinl IX (PPIX)-conjugated peptide formed nanomicelles (NM-PPIX) due to the improved enhanced permeability and retention (EPR) effect. Both the alleviated tumor hypoxia and improved tumor homing of photosensitizer (PS) molecules after PCPP treatment significantly increase the reactive oxygen species (ROS) generation in tumor and therefore realize greatly enhanced PDT effect of tumor in vivo.

A Versatile Carbon Monoxide Nanogenerator for Enhanced Tumor Therapy and Anti-Inflammation.

Carbon monoxide (CO) is regarded as a potential therapeutic agent with multiple beneficial functions for biomedical applications. In this study, a versatile CO nanogenerator (designated as PPOSD) was fabricated and developed for tumor therapy and anti-inflammation. Partially oxidized tin disulfide (SnS2) nanosheets (POS NSs) were decorated with a tumor-targeting polymer (polyethylene glycol-cyclo(Asp-d-Phe-Lys-Arg-Gly), PEG-cRGD), followed by the loading of chemotherapeutic drug doxorubicin (DOX) to prepare polymer@POS@DOX, or PPOSD. After injected intravenously, PPOSD could selectively accumulate in tumor tissue via the cRGD-mediated tumor recognition. Upon 561 nm laser irradiation, the POS moiety in PPOSD can photoreduce CO2 to CO, which significantly sensitized the chemotherapeutic effect of DOX. The POS in PPOSD can also act as a photothermal agent for effective photothermal therapy (PTT) of the tumor upon 808 nm laser irradiation. Furthermore, the generated CO can simultaneously decrease the inflammatory reaction caused by PTT. Blood analysis and hematoxylin-eosin staining of major organs showed that no obvious systemic toxicity was induced after the treatment, suggesting good biosafety of PPOSD. This versatile CO nanogenerator will find great potential for both enhanced tumor inhibition and anti-inflammation.

A tungsten nitride-based degradable nanoplatform for dual-modal image-guided combinatorial chemo-photothermal therapy of tumors.

An innovative tungsten-based multifunctional nanoplatform composed of polyethylene glycol (PEG)-modified tungsten nitride nanoparticles (WN NPs) is constructed for tumor treatment. The PEG-WN NPs not only possess strong near-infrared (NIR) absorbance, high photothermal conversion efficiency, and excellent photothermal stability, but also effectively inhibit tumor cells upon 808 nm laser irradiation. After coating with thiolated (2-hydroxypropyl)-ß-cyclodextrin (MUA-CD) on the surface, such a nanoplatform can also be used for drug delivery (such as DOX) and presents a synergistic tumor inhibition effect both in vitro and in vivo. Furthermore, the PEG-WN NPs present good contrasting capability for X-ray computed tomography (CT) and photoacoustic (PA) imaging. With PA/CT imaging, the tumor can be accurately positioned for precise treatment. It is worth mentioning that PEG-WN NPs are biodegradable and could be effectively excreted from the body with no appreciable toxicity in vivo. It is expected that this biocompatible multifunctional nanoplatform can serve as a potential candidate for tumor treatment in future clinical applications.

Regulation of prostate cancer by hormone-responsive G protein-coupled receptors.

Regulation of prostate cancer by androgen and androgen receptor (AR), and blockade of AR signaling by AR antagonists and steroidogenic enzyme inhibitors have been extensively studied. G protein-coupled receptors (GPCRs) are a family of membrane receptors that regulate almost all physiological processes. Nearly 40% of FDA-approved drugs in the market target GPCRs. A variety of GPCRs that mediate reproductive function have been demonstrated to be involved in the regulation of prostate cancer. These GPCRs include gonadotropin-releasing hormone receptor, luteinizing hormone receptor, follicle-stimulating hormone receptor, relaxin receptor, ghrelin receptor, and kisspeptin receptor. We highlight here GPCR regulation of prostate cancer by these GPCRs. Further therapeutic approaches targeting these GPCRs for the treatment of prostate cancer are summarized.

Identification of Oct4-activating compounds that enhance reprogramming efficiency.

One of the hurdles for practical application of induced pluripotent stem cells (iPSC) is the low efficiency and slow process of reprogramming. Octamer-binding transcription factor 4 (Oct4) has been shown to be an essential regulator of embryonic stem cell (ESC) pluripotency and key to the reprogramming process. To identify small molecules that enhance reprogramming efficiency, we performed a cell-based high-throughput screening of chemical libraries. One of the compounds, termed Oct4-activating compound 1 (OAC1), was found to activate both Oct4 and Nanog promoter-driven luciferase reporter genes. Furthermore, when added to the reprogramming mixture along with the quartet reprogramming factors (Oct4, Sox2, c-Myc, and Klf4), OAC1 enhanced the iPSC reprogramming efficiency and accelerated the reprogramming process. Two structural analogs of OAC1 also activated Oct4 and Nanog promoters and enhanced iPSC formation. The iPSC colonies derived using the Oct4-activating compounds along with the quartet factors exhibited typical ESC morphology, gene-expression pattern, and developmental potential. OAC1 seems to enhance reprogramming efficiency in a unique manner, independent of either inhibition of the p53-p21 pathway or activation of the Wnt-ß-catenin signaling. OAC1 increases transcription of the Oct4-Nanog-Sox2 triad and Tet1, a gene known to be involved in DNA demethylation.

DNA methylation and demethylation in mammals.

Cell type-specific DNA methylation patterns are established during mammalian development and maintained in adult somatic cells. Understanding how these patterns of 5-methylcytosine are established and maintained requires the elucidation of mechanisms for both DNA methylation and demethylation. The enzymes involved in the de novo methylation of DNA and the maintenance of the resulting methylation patterns have been fairly well characterized. However, important remaining challenges are to understand how DNA methylation systems function in vivo and in the context of chromatin. In addition, the enzymes and mechanisms for demethylation remain to be elucidated. There is still no consensus as to how active enzymatic demethylation is achieved in mammalian cells, but recent studies implicate base excision repair for genome-wide DNA demethylation in germ cells and early embryos.

CpG island clusters and pro-epigenetic selection for CpGs in protein-coding exons of HOX and other transcription factors.

CpG dinucleotides contribute to epigenetic mechanisms by being the only site for DNA methylation in mammalian somatic cells. They are also mutation hotspots and approximately 5-fold depleted genome-wide. We report here a study focused on CpG sites in the coding regions of Hox and other transcription factor genes, comparing methylated genomes of Homo sapiens, Mus musculus, and Danio rerio with nonmethylated genomes of Drosophila melanogaster and Caenorhabditis elegans. We analyzed 4-fold degenerate, synonymous codons with the potential for CpG. That is, we studied "silent" changes that do not affect protein products but could damage epigenetic marking. We find that DNA-binding transcription factors and other developmentally relevant genes show, only in methylated genomes, a bimodal distribution of CpG usage. Several genetic code-based tests indicate, again for methylated genomes only, that the frequency of silent CpGs in Hox genes is much greater than expectation. Also informative are NCG-GNN and NCC-GNN codon doublets, for which an unusually high rate of G to C and C to G transversions was observed at the third (silent) position of the first codon. Together these results are interpreted as evidence for strong "pro-epigenetic" selection acting to preserve CpG sites in coding regions of many genes controlling development. We also report that DNA-binding transcription factors and developmentally important genes are dramatically overrepresented in or near clusters of three or more CpG islands, suggesting a possible relationship between evolutionary preservation of CpG dinucleotides in both coding regions and CpG islands.

[Effects of PPAR-gamma agonist rosiglitazone on MMP-9 and TIMP-1 expression of monocyte-derived macrophages isolated from patients with acute coronary syndrome].

OBJECTIVE: Coronary arterial plaque rupture and secondary thrombosis are the major pathogenesis of acute coronary syndrome (ACS). Metalloprotease (MMPs) secreted by monocyte/macrophage was the main predisposing factor of the plaque rupture and peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is involved in a variety of inflammatory cytokine gene transcriptional regulations. We explored the possible role of PPAR-gamma in the regulation of MMP-9 and TIMP-1 expressed by peripheral monocyte-derived macrophages (MDMs) from patients with ACS. METHODS: Peripheral blood mononuclear cells were isolated from 48 patients with ACS and 28 healthy controls and stimulated by macrophage colony-stimulating factor (0.1 microg/ml for 24 hours) to form MDMs. MDMs were then incubated under various concentrations of rosiglitazone (0, 1, 10, 20 micromol/L) for 48 hours. The concentrations of MMP-9 and TIMP-1 in the supernatant were measured by enzyme linked immunosorbent assay, and the mRNA expression of PPAR-gamma, MMP-9 by RT-PCR and nuclear factor-kappaB P65 (NF-kappaB P65) expression by immunohistochemistry. RESULTS: PPAR-gamma mRNA expression was significantly lower while NF-kappaB P65 and MMP-9 expression as well as MMP-9 and TIMP-1 concentrations in supernatant were significantly higher in ACS group than those in control group (all P < 0.05). After rosiglitazone intervention, PPAR-gamma mRNA expression was significantly upregulated in both ACS and control groups in a dose-dependent manner. Both the MMP-9 concentration in the supernatant and MMP-9 mRNA expression were reduced post intervention with rosiglitazone in both groups. The TIMP-1 mRNA expression and concentration in supernatant were not affected by rosiglitazone in both groups. Rosiglitazone induced significant downregulation of NF-kappaB P65 expression in both groups. CONCLUSION: Rosiglitazone intervention may downregulate MMP-9 expression by upregulating PPAR-gamma expression, and by downregulating NF-kappaB expression in MDMs isolated from patients with ACS.

The histone methyltransferase SETDB1 and the DNA methyltransferase DNMT3A interact directly and localize to promoters silenced in cancer cells.

DNA CpG methylation can cooperate with histone H3 lysine 9 (H3-K9) methylation in heterochromatin formation and gene silencing. Trimethylation of H3-K9 by the recently identified euchromatic histone methyltransferase SETDB1/ESET may be responsible for transcriptional repression of certain promoters. Here, we show that SETDB1 associates with endogenous DNA methyltransferase activity. SETDB1 interacts with the de novo DNA methyltransferases DNMT3A and DNMT3B but not with the maintenance methyltransferase DNMT1. The interaction of SETDB1 with DNMT3A was further characterized and confirmed by in vivo and in vitro interaction studies. A direct interaction of the two proteins occurs through the N terminus of SETDB1 and the plant homeodomain of DNMT3A. Co-expression of SETDB1 and DNMT3A was essential for repression of reporter gene expression in a Gal4-based tethering assay and resulted in their recruitment to the artificial promoter. We further demonstrate that the CpG-methylated promoters of the endogenous p53BP2 gene in HeLa cells and the RASSF1A gene in MDA-MB-231 cells are simultaneously occupied by both SETDB1 and DNMT3A proteins, which provides evidence for SETDB1 being at least partly responsible for H3-K9 trimethylation at the promoter of RASSF1A, a gene frequently silenced in human cancers. In summary, our data demonstrate the direct physical interaction and functional connection between the H3-K9 trimethylase SETDB1 and the DNA methyltransferase DNMT3A and thus contribute to a better understanding of the complexity of the self-reinforcing heterochromatin machinery operating at silenced promoters.

Mutations in DNA methyltransferase DNMT3B in ICF syndrome affect its regulation by DNMT3L.

Deficiency in DNA methyltransferase DNMT3B causes a recessive human disorder characterized by immunodeficiency, centromeric instability and facial anomalies (ICF) in association with defects in genomic methylation. The majority of ICF mutations are single amino acid substitutions in the conserved catalytic domain of DNMT3B, which are believed to impair its enzymatic activity directly. The establishment of intact genomic methylation patterns in development requires a fine regulation of the de novo methylation activity of the two related methyltransferases DNMT3A and DNMT3B by regulatory factors including DNMT3L which has a stimulatory effect. Here, we show that two DNMT3B mutant proteins with ICF-causing substitution (A766P and R840Q) displayed a methylation activity similar to the wild-type enzyme both in vitro and in vivo. However, their stimulation by DNMT3L was severely compromised due to deficient protein interaction. Our findings suggest that methylation defects in ICF syndrome may also result from impaired stimulation of DNMT3B activity by DNMT3L or other unknown regulatory factors as well as from a weakened basal catalytic activity of the mutant DNMT3B protein per se.

The antisense strand of small interfering RNAs directs histone methylation and transcriptional gene silencing in human cells.

To determine mechanistically how siRNAs mediate transcriptional gene silencing (TGS) in human cells, we have measured histone methylation at targeted promoters, the dependency on active transcription, and whether or not both strands of the siRNA are required for siRNA-mediated TGS. We report here that siRNA treatment increases both H3K9 and H3K27 methylation of the targeted EF1A promoter and that this increase is dependent on nuclear specific delivery of the siRNA. We also find that TGS can be directed by the antisense strand alone, and requires active transcription by RNA polymerase II in human cells as evidenced by sensitivity to alpha-amanatin. The observation of antisense strand-specific siRNA-mediated TGS of EF1A was substantiated by targeting the U3 region of the HIV-1 LTR/promoter. Furthermore, we show that the antisense strand of siRNA EF52 associates with the transiently expressed Flag-tagged DNMT3A, the targeted EF1A promoter, and trimethylated H3K27. The observations reported here implicate a functional link between siRNA-mediated targeting of genomic regions (promoters), RNA Pol II function, histone methylation, and DNMT3A and support a paradigm in which the antisense strands of siRNAs alone can direct sequence-specific transcriptional gene silencing in human cells.

Maintenance and regulation of DNA methylation patterns in mammals.

Proper establishment and faithful maintenance of epigenetic information is crucial for the correct development of complex organisms. For mammals, it is now accepted that DNA methylation is an important mechanism for establishing stable heritable epigenetic marks. The distribution of methylation in the genome is not random, and patterns of methylated and unmethylated DNA are well regulated during normal development. The molecular mechanisms by which methylation patterns are established and maintained are complex and just beginning to be understood. In this review, we summarize recent progress in understanding the regulation of mammalian DNA methylation patterns, with an emphasis on the emerging roles of several protein and possible RNA factors. We also revisit the stochastic model of maintenance methylation and discuss its implications for epigenetic fidelity and gene regulation.

Physical and functional interactions between the human DNMT3L protein and members of the de novo methyltransferase family.

The de novo methyltransferase-like protein, DNMT3L, is required for methylation of imprinted genes in germ cells. Although enzymatically inactive, human DNMT3L was shown to act as a general stimulatory factor for de novo methylation by murine Dnmt3a. Several isoforms of DNMT3A and DNMT3B with development-stage and tissue-specific expression patterns have been described in mouse and human, thus bringing into question the identity of the physiological partner(s) for stimulation by DNMT3L. Here, we used an episome-based in vivo methyltransferase assay to systematically analyze five isoforms of human DNMT3A and DNMT3B for activity and stimulation by human DNMT3L. Our results show that human DNMT3A, DNMT3A2, DNMT3B1, and DNMT3B2 are catalytically competent, while DNMT3B3 is inactive in our assay. We also report that the activity of all four active isoforms is significantly increased upon co-expression with DNMT3L, albeit to varying extents. This is the first comprehensive description of the in vivo activities of the poorly characterized human DNMT3A and DNMT3B isoforms and of their functional interactions with DNMT3L. To further elucidate the mechanism by which DNMT3L stimulates DNA methylation, we have mapped in detail the domains that mediate interaction of human DNMT3L with human DNMT3A and DNMT3B. Our results show that the C-terminus of DNMT3L is the only region required for interaction with DNMT3A and DNMT3B and that interaction takes place through the C-terminal catalytic domain of DNMT3A and DNMT3B. The implications of these findings for the regulation of de novo methyltransferases and genomic imprinting are discussed. This article contains Supplementary Material available at http://www.mrw.interscience.wiley.com/suppmat/0730-2312/suppmat/2005/95/chen.html.