Curcumin inhibits hepatitis B virus infection by downregulating ccc DNA-bound histone acetylation

AIM To investigate the potential effect of curcumin on hepatitis B virus(HBV) covalently closed circular DNA(ccc DNA) and the underlying mechanism.METHODS A Hep G2.2.15 cell line stably transfected with HBV was treated with curcumin, and HBV surface antigen(HBs Ag) and e antigen(HBe Ag) expression levels were assessed by ELISA. Intracellular HBV DNA replication intermediates and ccc DNA were detected by Southern blot and real-time PCR, respectively. The acetylation levels of histones H3 and H4 were measured by Western blot. H3/H4-bound ccc DNA was detected by chromatin immunoprecipitation(Ch IP) assays. The deacetylase inhibitors trichostatin A and sodium butyrate were used to study the mechanism of action for curcumin. Additionally, short interfering RNAs(si RNAs) targeting HBV were tested along with curcumin.RESULTS Curcumin treatment led to time-and dose-dependent reductions in HBs Ag and HBe Ag expression and significant reductions in intracellular HBV DNA replication intermediates and HBV ccc DNA. After treatment with 20 μmol/L curcumin for 2 d, HBs Ag and ccc DNA levels in Hep G2.2.15 cells were reduced by up to 57.7%(P < 0.01) and 75.5%(P < 0.01), respectively, compared with levels in non-treated cells. Meanwhile, time-and dose-dependent reductions in the histone H3 acetylation levels were also detected upon treatment with curcumin, accompanied by reductions in H3-and H4-bound ccc DNA. Furthermore, the deacetylase inhibitors trichostatin A and sodium butyrate could block the effects of curcumin. Additionally, transfection of si RNAs targeting HBV enhanced the inhibitory effects of curcumin.CONCLUSION Curcumin inhibits HBV gene replication via downregulation of ccc DNA-bound histone acetylation and has the potential to be developed as a ccc DNA-targeting antiviral agent for hepatitis B.

Histone deacetylase inhibitors as a novel therapeutic approach for pheochromocytomas and paragangliomas

Epigenetic mechanisms,such as DNA methylation and histone modifications(e.g.,acetylation and deacetylation),are strongly implicated in the carcinogenesis of various malignancies.During transcription,the expression and functionality of coding gene products are altered following the histone acetylation and deacetylation.These processes are regulated by histone acetyltransferases(HATs)and histone deacetylases(HDACs),respectively.HDAC inhibitors(HDACis)have been developed as promising therapeutic agents,to limit exposure to traditional and toxic chemotherapies and offer more alternatives for some specific malignant diseases with limited options.Mechanistically,these agents affect many intracellular pathways,including cell cycle arrest,apoptosis and differentiation,and their mechanism of action mainly depends on the type of cancer.Currently,five HDACis have been approved for the treatment of several hematological malignancies(e.g.,T-cell lymphoma subtypes and multiple myeloma);while,many of them are tested for further therapeutic indications in solid tumors(e.g.,colorectal,thyroid,breast,lung and pancreatic cancer).Herein,we review the literature and gather all available evidence,from in vitro and in vivo data to clinical trial results,that recognizes the antitumor activity of HDACis on pheochromocytomas and paragangliomas;and supports their clinical implementation in the treatment of these rare neuroendocrine tumors at metastatic setting.

Curcumin-induced Histone Acetylation in Malignant Hematologic Cells

This study investigated the inhibitory effects of curcumin on proliferation of hematological malignant cells in vitro and the anti-tumor mechanism at histone acetylation/histone deacetylation levels. The effects of curcumin and histone deacetylase inhibitor trichostatin A （TSA） on the growth of Raji cells were tested by MTT assay. The expression of acetylated histone-3 （H3） in Raji, HL60 and K562 cells, and peripheral blood mononuclear cells （PBMCs） treated with curcumin or TSA was detected by immunohistochemistry and FACS. The results showed curcumin inhibited pro- liferation of Raji cells significantly in a time- and dose-dependent fashion, while exhibited low toxicity in PBMCs. Curcumin induced up-regulation of the expression of acetylated H3 dose-dependently in all malignant cell lines tested. In conclusion, curcumin inhibited proliferation of Raji cells selectively, enhanced the level of acetylated H3 in Raji, HL60, and K562 cells, which acted as a histone deacetylase inhibitor like TSA. Furthermore, up-regulation of H3 acetylation may play an important role in regulating the proliferation of Raji cells.

Targeting histone deacetylase suppresses tumor growth through eliciting METTL14-modified m^(6)A RNA methylation in ocular melanoma

Background Diversified histone deacetylation inhibitors(HDACis)have demonstrated encouraging outcomes in multiple malignancies.N6-methyladenine(m6A)is the most prevalent messenger RNA modification that plays an essential role in the regulation of tumorigenesis.Howbeit,an in-depth understanding of the crosstalk between histone acetylation and m6A RNA modifications remains enigmatic.This study aimed to explore the role of histone acetylation and m6A modifications in the regulation of tumorigenesis of ocular melanoma.Methods Histone modification inhibitor screening was used to explore the effects of HDACis on ocular melanoma cells.Dot blot assay was used to detect the global m6A RNA modification level.Multi-omics assays,including RNA-sequencing,cleavage under targets and tagmentation,single-cell sequencing,methylated RNA immunoprecipitation-sequencing(meRIP-seq),and m6A individual nucleotide resolution cross-linking and immunoprecipitation-sequencing(miCLIP-seq),were performed to reveal the mechanisms of HDACis on methyltransferase-like 14(METTL14)and FAT tumor suppressor homolog 4(FAT4)in ocular melanoma.Quantitative real-time polymerase chain reaction(qPCR),western blotting,and immunofluorescent staining were applied to detect the expression of METTL14 and FAT4 in ocular melanoma cells and tissues.Cell models and orthotopic xenograft models were established to determine the roles of METTL14 and FAT4 in the growth of ocular melanoma.RNA-binding protein immunoprecipitation-qPCR,meRIP-seq,miCLIP-seq,and RNA stability assay were adopted to investigate the mechanism by which m6A levels of FAT4 were affected.Results First,we found that ocular melanoma cells presented vulnerability towards HDACis.HDACis triggered the elevation of m6A RNA modification in ocular melanoma.Further studies revealed that METTL14 served as a downstream candidate for HDACis.METTL14 was silenced by the hypo-histone acetylation status,whereas HDACi restored the normal histone acetylation level of METTL14,thereby inducing its expression.Subsequently,METTL14 served as a tumor suppressor by promoting the expression of FAT4,a tumor suppressor,in a m6A-YTH N6-methyladenosine RNA-binding protein 1-dependent manner.Taken together,we found that HDACi restored the histone acetylation level of METTL14 and subsequently elicited METTL14-mediated m6A modification in tumorigenesis.Conclusions These results demonstrate that HDACis exert anti-cancer effects by orchestrating m6A modification,which unveiling a“histone-RNA crosstalk”of the HDAC/METTL14/FAT4 epigenetic cascade in ocular melanoma.

The chromatin remodeler BRAHMA recruits HISTONE DEACETYLASE6 to regulate root growth inhibition in response to phosphate starvation in Arabidopsis

Plasticity in root system architecture(RSA)allows plants to adapt to changing nutritional status in the soil.Phosphorus availability is a major determinant of crop yield,and RSA remodeling is critical to increasing the efficiency of phosphorus acquisition.Although substantial progress has been made in understanding the signaling mechanism driving phosphate starvation responses in plants,whether and how epigenetic regulatory mechanisms contribute is poorly understood.Here,we report that the Switch defective/sucrose non-fermentable(SWI/SNF)ATPase BRAHMA(BRM)is involved in the local response to phosphate(Pi)starvation.The loss of BRM function induces iron(Fe)accumulation through increased LOW PHOSPHATE ROOT1(LPR1)and LPR2 expression,reducing primary root length under Pi deficiency.We also demonstrate that BRM recruits the histone deacetylase(HDA)complex HDA6-HDC1 to facilitate histone H3 deacetylation at LPR loci,thereby negatively regulating local Pi deficiency responses.BRM is degraded under Pi deficiency conditions through the 26 S proteasome pathway,leading to increased histone H3 acetylation at the LPR loci.Collectively,our data suggest that the chromatin remodeler BRM,in concert with HDA6,negatively regulates Fe-dependent local Pi starvation responses by transcriptionally repressing the RSA-related genes LPR1 and LPR2 in Arabidopsis thaliana.

The Intronic cis Element SE1 Recruits trans-Acting Repressor Complexes to Repress the Expression of ELONGATED UPPERMOST INTERNODE1 in Rice

Plant height has a major effect on grain yield in crops such as rice （Oryza sativa）, and the hormone gibberellic acid （GA） regulates many developmental processes that feed into plant height. Rice ELONGATED UPPERMOST INTERNODE1 （Euil） encodes a GA-deactivating enzyme governing elongation of the uppermost internode. The expression of Euil is finely tuned, thereby maintaining homeostasis of endogenous bioactive GA and producing plants of normal plant height. Here, we identified a dominant dwarf mutant, dEuil, caused by the deletion of an RY motif-containing cis-silencing element （SE1） in the intron of Euil. Detailed genetic and molecular analysis of SE1 revealed that this intronic cis element recruits at least one trans-acting repressor complex, containing the B3 repressors OsVAL2 and OsGD1, the SAP18 corepressor, and the histone deacetylase OsHDA710, to negatively regulate the expression of Euil. This com- plex generates closed chromatin at Euil, suppressing Euil expression and modulating GA homeostasis. Loss of SE1 or dysfunction of the complex components impairs histone deacetylation and H3K27me3 methylation of Euil chromatin, thereby increasing Euil transcription and decreasing bioactive GA, producing dwarfism in rice. Together, our results reveal a novel silencing mechanism in which the intronic cis element SE1 negatively regulates Euil expression via repressor complexes that modulate histone deacetylation and/or methylation.