On your histone mark, SET, methylate!

Histone H2B lysine 122 and lysine 130, as the putative targets of Penicillium oxalicum LaeA, play important roles in asexual development, expression of secondary metabolite gene clusters, and extracellular glycoside hydrolase synthesis

Core histones in the nucleosome are subject to a wide variety of posttranslational modifications (PTMs), such as methylation, phosphorylation, ubiquitylation, and acetylation, all of which are crucial in shaping the structure of the chromatin and the expression of the target genes. A putative histone methyltransferase LaeA/Lae1, which is conserved in numerous filamentous fungi, functions as a global regulator of fungal growth, virulence, secondary metabolite formation, and the production of extracellular glycoside hydrolases (GHs). LaeA's direct histone targets, however, were not yet recognized. Previous research has shown that LaeA interacts with core histone H2B. Using S-adenosyl-L-methionine (SAM) as a methyl group donor and recombinant human histone H2B as the substrate, it was found that Penicillium oxalicum LaeA can transfer the methyl groups to the C-terminal lysine (K) 108 and K116 residues in vitro. The H2BK108 and H2BK116 sites on recombinant histone correspond to P. oxalicum H2BK122 and H2BK130, respectively. H2BK122A and H2BK130A, two mutants with histone H2B K122 or K130 mutation to alanine (A), were constructed in P. oxalicum. The mutants H2BK122A and H2BK130A demonstrated altered asexual development and decreased extracellular GH production, consistent with the findings of the laeA gene deletion strain (ΔlaeA). The transcriptome data showed that when compared to wild-type (WT) of P. oxalicum, 38 of the 47 differentially expressed (fold change ≥ 2, FDR ≤ 0.05) genes that encode extracellular GHs showed the same expression pattern in the three mutants ΔlaeA, H2BK122A, and H2BK130A. The four secondary metabolic gene clusters that considerably decreased expression in ΔlaeA also significantly decreased in H2BK122A or H2BK130A. The chromatin of promotor regions of the key cellulolytic genes cel7A/cbh1 and cel7B/eg1 compacted in the ΔlaeA, H2BK122A, and H2BK130A mutants, according to the results of chromatin accessibility real-time PCR (CHART-PCR). The chromatin accessibility index dropped. The histone binding pocket of the LaeA-methyltransf_23 domain is compatible with particular histone H2B peptides, providing appropriate electrostatic and steric compatibility to stabilize these peptides, according to molecular docking. The findings of the study demonstrate that H2BK122 and H2BK130, which are histone targets of P. oxalicum LaeA in vitro, are crucial for fungal conidiation, the expression of gene clusters encoding secondary metabolites, and the production of extracellular GHs.

Alterations in Histone Methylation States Increased Profusion of Lethal(2)-Essential-for-Life-Like (l(2)elf), Trithorax and Polycomb Genes in Apis mellifera under Heat Stress

Histone post-translational modifications (PTMs) represent a key mechanism in the thermal adaptation of the honeybee Apis mellifera. In this study, a chromatin immunoprecipitation assay and qPCR were employed to explore the changes in the methylation states of H3K4m2, H3K4m3, H3K27m2 and H3K27m3 associated with l2efl (ID: 72474, 724405, 724488), histone methyltransferases (HMTs) ((trx) and PR-set7) and Polycomb (Pc) and (Su(z)12) genes in A. m. jemenitica (tolerant subspecies) and A. m. carnica (susceptible subspecies) in response to heat treatment (42 °C for 1 h). The results revealed significant enrichment fold changes in the methylation/demethylation of most H3K4 and H3K27 marks at all targeted genes. These changes increased the profusion of l2efl (ID: 72474, 724405, 724488), histone methyltransferases (HMTs) (trx) and Polycomb (Pc) and Su(z)12 and decreased the profusion of HMT (PR-set7) in both honeybee subspecies. The changes in the methylation enrichment folds of histone methyltransferases (HMTs) ((trx), PR-set) and Polycomb (Pc), Su(z)12 genes demonstrate the well-harmonized coordination of epigenetic gene regulation in response to heat treatment. Compared to the control, the changes in the methylation enrichment folds of H3K4m3 at Polycomb Su(z)12 were about 30× and 100× higher in treated A. m. jemenitica and A.m. carnica, respectively. Similarly, changes in the methylation/demethylation enrichment folds of HMT (trx) and Polycomb (Pc) and Su(z)12 were 2-3× higher in A. m. carnica than in A. m. jemenitica after treatment (42 °C). It is evident that post-translational chromatin modification in both honeybee subspecies can diminish heat stress impact by (I) increasing the transcriptional provision of l2efl associated with survival and (II) increasing the silencing of genes associated with general cellular activities.

SETD7 promotes metastasis of triple-negative breast cancer by YY1 lysine methylation

Breast cancer has gradually become the predominant cause for cancer-associated death in women. The metastatic dissemination and underlying mechanisms of triple-negative breast cancer (TNBC) are not sufficiently understood. (Su(var)3-9, enhancer of zeste, Trithorax) domain-containing protein 7 (SETD7) is vital for promoting the metastasis of TNBC, as demonstrated in this study. Clinical outcomes were significantly worse in primary metastatic TNBC with upregulated SETD7. Overexpression of SETD7 in vitro and in vivo promotes migration of TNBC cells. Two highly conserved lysine (K) residues K173 and K411 of Yin Yang 1 (YY1) are methylated by SETD7. Further, we found that SETD7-mediated K173 residue methylation protects YY1 from the ubiquitin-proteasome degradation. Mechanistically, it was found that the SETD7/YY1 axis regulates epithelial-mesenchymal transition (EMT) and tumor cell migration via the ERK/MAPK pathway in TNBC. The findings indicated that TNBC metastasis is driven by a novel pathway, which may be a promising target for advanced TNBC treatment.

Expression Levels of Heat-Shock Proteins in Apis mellifera jemenetica and Apis mellifera carnica Foragers in the Desert Climate of Saudi Arabia

A. m. jemenetica is the indigenous honeybee of the Arabian Peninsula. It is highly adapted to extreme temperatures exceeding 40 °C, yet important molecular aspects of its adaptation are not well documented. In this study we quantify relative expression levels of small- and large-molecular-weight heat-shock proteins (hsp10, hsp28, hsp70, hsp83, hsp90 and hsc70 (mRNAs)) in the thermos-tolerant A. m. jemenetica and thermosusceptible A. m. carnica forager honeybee subspecies under desert (Riyadh) and semi-arid (Baha) summer conditions. The results showed significant day-long higher expression levels of hsp mRNAs in A. m. jemenetica compared to A. m. carnica under the same conditions. In Baha, the expression levels were very modest in both subspecies compared those in Riyadh though the expression levels were higher in A. m. jemenetica. The results also revealed a significant interaction between subspecies, which indicated milder stress conditions in Baha. In conclusion, the higher expression levels of hsp10, hsp28, hsp70ab, hsp83 and hsp90 mRNAs in A. m. jemenetica are key elements in the adaptive nature of A. m. jemenetica to local conditions that enhance its survival and fitness in high summer temperatures.

Linking Histone Methylation States and hsp Transcriptional Regulation in Thermo-Tolerant and Thermo-Susceptible A. mellifera L. Subspecies in Response to Heat Stress

Genetic and epigenetic responses to environmental cues of worker honeybees mediate hsp synthesis, a key mechanism to tolerate high ambient temperatures in Apis mellifera. In this study, the chromatin immunoprecipitation assay followed by qPCR were used to determine alterations in histone methylation states (H3K27me2, H3K27me3, H3K4me2, and H3K4me3) associated with hsp/hsc/trx in A. m. jemenetica (thermo-tolerant subspecies) and A. m. carnica (thermo-susceptible subspecies) after heat treatment. The results revealed significant changes in enrichment folds of histone methylation states associated with hsp/hsc/trx. Indeed, the enrichment of H3K27me2 decreased strongly in response to heat stress. Changes in histone methylation states were significantly higher in A. m. carnica samples compared to A. m. jemenitica samples. Our study provides a new perception on linking histone post-translational methylation as an epigenetic mechanism of gene regulation with hsp/hsc/trx in A. mellifera subspecies exposed to heat stress.

SETD6 Regulates E2-Dependent Human Papillomavirus Transcription

Human papillomaviruses (HPV) cause cervical, anogenital, and oral cancers. Brd4 plays an important role in the HPV life cycle. SETD6 was recently shown to methylate Brd4. The current study demonstrates that methylation of Brd4 by SETD6 in HPV-episomal cells is required for the activation of viral transcription. This study illustrates a novel regulatory mechanism involving E2, Brd4, and SETD6 in the HPV life cycle and provides insight into the multiple roles of Brd4 in viral pathogenesis.

The histone code of the fungal genus Aspergillus uncovered by evolutionary and proteomic analyses

Chemical modifications of DNA and histone proteins impact the organization of chromatin within the nucleus. Changes in these modifications, catalysed by different chromatin-modifying enzymes, influence chromatin organization, which in turn is thought to impact the spatial and temporal regulation of gene expression. While combinations of different histone modifications, the histone code, have been studied in several model species, we know very little about histone modifications in the fungal genus Aspergillus, whose members are generally well studied due to their importance as models in cell and molecular biology as well as their medical and biotechnological relevance. Here, we used phylogenetic analyses in 94 Aspergilli as well as other fungi to uncover the occurrence and evolutionary trajectories of enzymes and protein complexes with roles in chromatin modifications or regulation. We found that these enzymes and complexes are highly conserved in Aspergilli, pointing towards a complex repertoire of chromatin modifications. Nevertheless, we also observed few recent gene duplications or losses, highlighting Aspergillus species to further study the roles of specific chromatin modifications. SET7 (KMT6) and other components of PRC2 (Polycomb Repressive Complex 2), which is responsible for methylation on histone H3 at lysine 27 in many eukaryotes including fungi, are absent in Aspergilli as well as in closely related Penicillium species, suggesting that these lost the capacity for this histone modification. We corroborated our computational predictions by performing untargeted MS analysis of histone post-translational modifications in Aspergillus nidulans. This systematic analysis will pave the way for future research into the complexity of the histone code and its functional implications on genome architecture and gene regulation in fungi.

Post-Translational Modifications of Histones Are Versatile Regulators of Fungal Development and Secondary Metabolism

Chromatin structure is a major regulator of DNA-associated processes, such as transcription, DNA repair, and replication. Histone post-translational modifications, or PTMs, play a key role on chromatin dynamics. PTMs are involved in a wide range of biological processes in eukaryotes, including fungal species. Their deposition/removal and their underlying functions have been extensively investigated in yeasts but much less in other fungi. Nonetheless, the major role of histone PTMs in regulating primary and secondary metabolisms of filamentous fungi, including human and plant pathogens, has been pinpointed. In this review, an overview of major identified PTMs and their respective functions in fungi is provided, with a focus on filamentous fungi when knowledge is available. To date, most of these studies investigated histone acetylations and methylations, but the development of new methodologies and technologies increasingly allows the wider exploration of other PTMs, such as phosphorylation, ubiquitylation, sumoylation, and acylation. Considering the increasing number of known PTMs and the full range of their possible interactions, investigations of the subsequent Histone Code, i.e., the biological consequence of the combinatorial language of all histone PTMs, from a functional point of view, are exponentially complex. Better knowledge about histone PTMs would make it possible to efficiently fight plant or human contamination, avoid the production of toxic secondary metabolites, or optimize the industrial biosynthesis of certain beneficial compounds.

Expression of the histone lysine methyltransferases SETD1B, SETDB1, SETD2, and CFP1 exhibits significant changes in the oocytes and granulosa cells of aged mouse ovaries

Histone methylation is one of the main epigenetic mechanisms by which methyl groups are dynamically added to the lysine and arginine residues of histone tails in nucleosomes. This process is catalyzed by specific histone methyltransferase enzymes. Methylation of these residues promotes gene expression regulation through chromatin remodeling. Functional analysis and knockout studies have revealed that the histone lysine methyltransferases SETD1B, SETDB1, SETD2, and CFP1 play key roles in establishing the methylation marks required for proper oocyte maturation and follicle development. As oocyte quality and follicle numbers progressively decrease with advancing maternal age, investigating their expression patterns in the ovaries at different reproductive periods may elucidate the fertility loss occurring during ovarian aging. The aim of our study was to determine the spatiotemporal distributions and relative expression levels of the Setd1b, Setdb1, Setd2, and Cxxc1 (encoding the CFP1 protein) genes in the postnatal mouse ovaries from prepuberty to late aged periods. For this purpose, five groups based on their reproductive periods and histological structures were created: prepuberty (3 weeks old; n = 6), puberty (7 weeks old; n = 7), postpuberty (18 weeks old; n = 7), early aged (52 weeks old; n = 7), and late aged (60 weeks old; n = 7). We found that Setd1b, Setdb1, Setd2, and Cxxc1 mRNA levels showed significant changes among postnatal ovary groups (P < 0.05). Furthermore, SETD1B, SETDB1, SETD2, and CFP1 proteins exhibited different subcellular localizations in the ovarian cells, including oocytes, granulosa cells, stromal and germinal epithelial cells. In general, their levels in the follicles, oocytes, and granulosa cells as well as in the germinal epithelial and stromal cells significantly decreased in the aged groups when compared the other groups (P < 0.05). These decreases were concordant with the reduced numbers of the follicles at different stages and the luteal structures in the aged groups (P < 0.05). In conclusion, these findings suggest that altered expression of the histone methyltransferase genes in the ovarian cells may be associated with female fertility loss in advancing maternal age.

Diabetes Mellitus Is a Chronic Disease that Can Benefit from Therapy with Induced Pluripotent Stem Cells

Diabetes mellitus (DM) is one of the main causes of morbidity and mortality, with an increasing incidence worldwide. The impact of DM on public health in developing countries has triggered alarm due to the exaggerated costs of the treatment and monitoring of patients with this disease. Considerable efforts have been made to try to prevent the onset and reduce the complications of DM. However, because insulin-producing pancreatic β-cells progressively deteriorate, many people must receive insulin through subcutaneous injection. Additionally, current therapies do not have consistent results regarding the prevention of chronic complications. Leveraging the approval of real-time continuous glucose monitors and sophisticated algorithms that partially automate insulin infusion pumps has improved glycemic control, decreasing the burden of diabetes management. However, these advances are facing physiologic barriers. New findings in molecular and cellular biology have produced an extraordinary advancement in tissue development for the treatment of DM. Obtaining pancreatic β-cells from somatic cells is a great resource that currently exists for patients with DM. Although this therapeutic option has great prospects for patients, some challenges remain for this therapeutic plan to be used clinically. The purpose of this review is to describe the new techniques in cell biology and regenerative medicine as possible treatments for DM. In particular, this review highlights the origin of induced pluripotent cells (iPSCs) and how they have begun to emerge as a regenerative treatment that may mitigate the pathology of this disease.

ARTP/EMS-combined multiple mutagenesis efficiently improved production of raw starch-degrading enzymes in Penicillium oxalicum and characterization of the enzyme-hyperproducing mutant

BACKGROUND

Application of raw starch-degrading enzymes (RSDEs) in starch processing for biofuel production can effectively reduce energy consumption and processing costs. RSDEs are generally produced by filamentous fungi, such as Penicillium oxalicum, but with very low yields, which seriously hampers industrialization of raw starch processing. Breeding assisted by random mutagenesis is an efficient way to improve fungal enzyme production.

RESULTS

A total of 3532 P. oxalicum colonies were generated after multiple rounds of mutagenesis, by atmospheric and room-temperature plasma (ARTP) and/or ethyl methanesulfonate (EMS). Of these, one mutant A2-13 had the highest RSDE activity of 162.7 U/mL, using raw cassava flour as substrate, a yield increase of 61.1%, compared with that of the starting strain, OXPoxGA15A. RSDE activity of A2-13 further increased to 191.0 U/mL, through optimization of culture conditions. Increased expression of major amylase genes, including the raw starch-degrading glucoamylase gene, PoxGA15A, and its regulatory gene, PoxAmyR, as well as several single-nucleotide polymorphisms in the A2-13 genome, were detected by real-time reverse transcription quantitative PCR and genomic re-sequencing, respectively. In addition, crude RSDEs produced by A2-13, combined with commercial α-amylase, could efficiently digest raw corn flour and cassava flour at 40 °C.

CONCLUSIONS

Overall, ARTP/EMS-combined mutagenesis effectively improved fungal RSDE yield. An RSDE-hyperproducing mutant, A2-13, was obtained, and its RSDEs could efficiently hydrolyze raw starch, in combination with commercial α-amylase at low temperature, which provides a useful RSDE resource for future starch processing.

Histone methyltransferase SETDB1 promotes colorectal cancer proliferation through the STAT1-CCND1/CDK6 axis

Upregulation of histone methyltransferase SET domain bifurcated 1 (SETDB1) is associated with poor prognosis in cancer patients. However, the mechanism of oncogenicity of SETDB1 in cancer is hitherto unknown. Here, we show that SETDB1 is upregulated in human colorectal cancer (CRC) where its level correlates with poor clinical outcome. Ectopic SETDB1 promotes CRC cell proliferation, whereas SETDB1 attenuation inhibits this process. Flow cytometry reveals that SETDB1 promotes proliferation by driving the CRC cell cycle from G0/G1 phase to S phase. Mechanistically, SETDB1 binds directly to the STAT1 promoter region resulting in increased STAT1 expression. Functional characterization reveals that STAT1-CCND1/CDK6 axis is a downstream effector of SETDB1-mediated CRC cell proliferation. Furthermore, SETDB1 upregulation is sufficient to accelerate in vivo proliferation in xenograft animal model. Taken together, our results provide insight into the upregulation of SETDB1 within CRC and can lead to novel treatment strategies targeting this cell proliferation-promoting gene.

Insights on the regulation of the MLL/SET1 family histone methyltransferases

In eukaryotes, histone H3K4 methylation by the MLL/SET1 family histone methyltransferases is enriched at transcription regulatory elements including gene promoters and enhancers. The level of H3K4 methylation is highly correlated with transcription activation and is one of the most frequently used histone post-translational modifications to predict transcriptional outcome. Recently, it has been shown that rearrangement of the cellular landscape of H3K4 mono-methylation at distal enhancers precedes cell fate transition and is used for identification of novel regulatory elements for development and disease progression. Similarly, broad H3K4 tri-methylation regions have also been used to predict intrinsic tumor suppression properties of regulator regions in a variety of cellular models. Understanding the regulation for how H3K4 methylation is deposited and regulated is of paramount importance. In this review, we will discuss new findings on how the MLL/SET1 family enzymes are regulated on chromatin and their potential functional and regulatory implications. This article is part of a Special Issue entitled: The MLL family of proteins in normal development and disease edited by Thomas A Milne.

The Indispensable Role of Histone Methyltransferase PoDot1 in Extracellular Glycoside Hydrolase Biosynthesis of Penicillium oxalicum

Histone methylation is associated with transcription regulation, but its role for glycoside hydrolase (GH) biosynthesis is still poorly understood. We identified the histone H3 lysine 79 (H3K79)-specific methyltransferase PoDot1 in Penicillium oxalicum. PoDot1 affects conidiation by regulating the transcription of key regulators (BrlA, FlbC, and StuA) of asexual development and is required in normal hyphae septum and branch formation by regulating the transcription of five septin-encoding genes, namely, aspA, aspB, aspC, aspD, and aspE. Tandem affinity purification/mass spectrometry showed that PoDot1 has no direct interaction with transcription machinery, but it affects the expressions of extracellular GH genes extensively. The expression of genes (amy15A, amy13A, cel7A/cbh1, cel61A, chi18A, cel3A/bgl1, xyn10A, cel7B/eg1, cel5B/eg2, and cel6A/cbh2) that encode the top 10 GHs was remarkably downregulated by Podot1 deletion (ΔPodot1). Consistent with the decrease in gene transcription level, the activities of amylases and cellulases were significantly decreased in ΔPodot1 mutants in agar (solid) and fermentation (liquid) media. The repression of GH gene expressions caused by PoDot1 deletion was not mediated by key transcription factors, such as AmyR, ClrB, CreA, and XlnR, but was accompanied by defects in global demethylated H3K79 (H3K79me2) and trimethylated H3K79 (H3K79me3). The impairment of H3K79me2 on specific GH gene loci was observed due to PoDot1 deletion. The results implies that defects of H3K79 methylation is the key reason of the downregulated transcription level of GH-encoding genes and reveals the indispensable role of PoDot1 in extracellular GH biosynthesis.

Normal transcription of cellulolytic enzyme genes relies on the balance between the methylation of H3K36 and H3K4 in Penicillium oxalicum

BACKGROUND

Enzymatic hydrolysis of lignocellulose by fungi is a key step in global carbon cycle and biomass utilization. Cellulolytic enzyme production is tightly controlled at a transcriptional level. Here, we investigated the roles of different histone lysine methylation modifications in regulating cellulolytic enzyme gene expression, as histone lysine methylation is an important process of chromatin regulation associated with gene transcription.

RESULTS

PoSet1 and PoSet2 in Penicillium oxalicum, orthologs of Set1 and Set2 in budding yeast, were associated with the methylation of histone H3 lysine 4 (H3K4) and lysine 36 (H3K36). Cellulolytic enzyme production was extensively upregulated by the disruption of PoSet2, but was significantly downregulated by the disruption of PoSet1. We revealed that the activation of cellulolytic enzyme genes was accompanied by the increase of H3K4me3 signal, as well as the decrease of H3K36me1 and H3K36me3 signal on specific gene loci. The repression of cellulolytic enzyme genes was accompanied by the absence of global H3K4me1 and H3K4me2. An increase in the H3K4me3 signal by Poset2 disruption was eliminated by the further disruption of Poset1 and accompanied by the repressed cellulolytic enzyme genes. The active or repressed genes were not always associated with transcription factors.

CONCLUSION

H3K4 methylation is an active marker of cellulolytic enzyme production, whereas H3K36 methylation is a marker of repression. A crosstalk occurs between H3K36 and H3K4 methylation, and PoSet2 negatively regulates cellulolytic enzyme production by antagonizing the PoSet1-H3K4me3 pathway. The balance of H3K4 and H3K36 methylation is required for the normal transcription of cellulolytic enzyme genes. These results extend our previous understanding that cellulolytic enzyme gene transcription is primarily controlled by transcription factors.

Lysine methyltransferase SETD6 modifies histones on a glycine-lysine motif

Although central to regulating the access to genetic information, most lysine methyltransferases remain poorly characterised relative to other family of enzymes. Herein, I report new substrates for the lysine methyltransferase SETD6. Based on the SETD6-catalysed site on the histone variant H2AZ, I identified similar sequences in the canonical histones H2A, H3, and H4 that are modified by SETD6 in vitro, and putative non-histone substrates. I herein expend the repertoire of substrates for methylation by SETD6.

Lysine methylation of transcription factors in cancer

Protein lysine methylation is a critical and dynamic post-translational modification that can regulate protein stability and function. This post-translational modification is regulated by lysine methyltransferases and lysine demethylases. Recent studies using mass-spectrometric techniques have revealed that in addition to histones, a great number of transcription factors are also methylated, often at multiple sites and to different degrees (mono-, di-, trimethyl lysine). The biomedical significance of transcription factor methylation in human diseases, including cancer, has been explored recently. Some studies have demonstrated that interfering with transcription factor lysine methylation both in vitro and in vivo can inhibit cancer cell proliferation, thereby reversing tumor progression. The inhibitors targeting lysine methyltransferases and lysine demethylases have been under development for the past two decades, and may be used as potential anticancer agents in the clinic. In this review, we focus on the current findings of transcription factor lysine methylation, and the effects on both transcriptional activity and target gene expression. We outlined the biological significance of transcription factor lysine methylation on tumor progression and highlighted its clinical value in cancer therapy.

Hibernation impacts lysine methylation dynamics in the 13-lined ground squirrel, Ictidomys tridecemlineatus

During winter hibernation in mammals, body temperature falls to near-ambient levels, metabolism shifts to favor lipid oxidation, and metabolic rate is strongly suppressed by inhibiting many ATP-expensive processes (e.g., transcription, translation) for animals in order to survive for many months on limited reserves of body fuels. Regulation of such profound changes (i.e., metabolic rate depression) requires rapid and reversible controls provided by protein posttranslational modifications. Protein lysine methylation provides one mechanism by which the functionality, activity, and stability of cellular proteins and enzymes can be modified for the needs of the hibernator. The present study reports the responses of seven lysine methyltransferases (SMYD2, SUV39H1, SET8, SET7/9, G9a, ASH2L, and RBBP5) in skeletal muscle and liver over seven stages of the torpor/arousal cycle in 13-lined ground squirrels (Ictidomys tridecemlineatus). A tissue-specific and stage-specific analysis revealed significant changes in the protein levels of lysine methyltransferases, methylation patterns on histone H3, histone methyltransferase activity, and methylation of the p53 transcription factor. Enzymes typically increased in protein amount in either torpor, arousal, or the transitory periods. Methylation of histone H3 and p53 typically followed the patterns of the methyltransferase enzymes. Overall, these data show that protein lysine methylation is an important regulator of the mammalian hibernation phenotype.

Post-translational Modification Control of HBV Biological Processes

Hepatitis B virus infection remains a global healthy issue that needs to be urgently solved. Novel strategies for anti-viral therapy are based on exploring the effective diagnostic markers and therapeutic targets of diseases caused by hepatitis B virus (HBV) infection. It is well-established that not only viral proteins themselves but also key factors from the host control the biological processes associated with HBV, including replication, transcription, packaging, and secretion. Protein post-translational modifications (PTMs), such as phosphorylation, acetylation, methylation, and ubiquitination, have been shown to control protein activity, regulate protein stability, promote protein interactions and alter protein subcellular localization, leading to the modulation of crucial signaling pathways and affected cellular processes. This review focuses on the functions and effects of diverse PTMs in regulating important processes in the HBV life cycle. The potential roles of PTMs in the pathogenesis of HBV-associated liver diseases are also discussed.

Mass spectrometry and DigiWest technology emphasize protein acetylation profile from Quisinostat-treated HuT78 CTCL cell line

Histone deacetylases (HDACs) are key enzymes involved in epigenetic modulation and were targeted by HDAC inhibitors (HDACis) for cancer treatment. The action of HDACis is not restricted to histones and also prevents deacetylation of other proteins, supporting their wide biological actions. The HuT78 cell line is recognized as a key tool to support and understand cutaneous T-cell lymphoma (CTCL) biology and was used as a predictive model since HDACi such as Vorinostat and Panobinostat have both demonstrated apoptotic activities in HuT78 cells and in primary blood CTCL cells. In this study, Quisinostat (JNJ-26481585) a novel second-generation HDACi with highest potency for HDAC1, was tested on HuT78 cell line. Quantitative mass spectrometry (MS)-based proteomics after acetylated-lysine peptide enrichment and a targeted antibody-based immunoassay (DigiWest) were used as complementary technologies to assess the modifications of the acetylated proteome. As expected, several acetylated lysines of histones were increased by the HDACi. Additional acetylated non-histone proteins were modulated after treatment with Quisinostat including the nucleolin (a major nucleolar protein), the replication protein A 70 kDa DNA-binding subunit, the phosphoglycerate kinase 1, the stress-70 protein, the proto-oncogene Myc and the serine hydroxymethyltransferase. A better knowledge of histone and non-histone acetylated protein profile after Quisinostat treatment can strongly support the understanding of non-clinical and clinical results of this HDACi. These technological tools can also help in designing new HDACis in a pharmaceutical drug discovery program.

SIGNIFICANCE

A better knowledge of histone and non-histone acetylated protein profile after HDAC inhibitors (HDACis) treatment can strongly support the understanding of non-clinical and clinical investigations in a pharmaceutical drug discovery program. Relative quantification using mass spectrometry -based proteomics after acetylated-lysine peptide enrichment and a targeted antibody-based immunoassay (DigiWest) are proposed as complementary technologies to assess the modifications of the acetylated proteome. Quisinostat (JNJ-26481585) a novel second-generation HDACi with highest potency for HDAC1 was better characterized in vitro in HuT78 cells to support and understand cutaneous T-cell lymphoma (CTCL) therapeutic research program.

Lung Cancer Therapy Targeting Histone Methylation: Opportunities and Challenges

Lung cancer is one of the most common malignancies. In spite of the progress made in past decades, further studies to improve current therapy for lung cancer are required. Dynamically controlled by methyltransferases and demethylases, methylation of lysine and arginine residues on histone proteins regulates chromatin organization and thereby gene transcription. Aberrant alterations of histone methylation have been demonstrated to be associated with the progress of multiple cancers including lung cancer. Inhibitors of methyltransferases and demethylases have exhibited anti-tumor activities in lung cancer, and multiple lead candidates are under clinical trials. Here, we summarize how histone methylation functions in lung cancer, highlighting most recent progresses in small molecular inhibitors for lung cancer treatment.

Histone Lysine Methylases and Demethylases in the Landscape of Human Developmental Disorders

Histone lysine methyltransferases (KMTs) and demethylases (KDMs) underpin gene regulation. Here we demonstrate that variants causing haploinsufficiency of KMTs and KDMs are frequently encountered in individuals with developmental disorders. Using a combination of human variation databases and existing animal models, we determine 22 KMTs and KDMs as additional candidates for dominantly inherited developmental disorders. We show that KMTs and KDMs that are associated with, or are candidates for, dominant developmental disorders tend to have a higher level of transcription, longer canonical transcripts, more interactors, and a higher number and more types of post-translational modifications than other KMT and KDMs. We provide evidence to firmly associate KMT2C, ASH1L, and KMT5B haploinsufficiency with dominant developmental disorders. Whereas KMT2C or ASH1L haploinsufficiency results in a predominantly neurodevelopmental phenotype with occasional physical anomalies, KMT5B mutations cause an overgrowth syndrome with intellectual disability. We further expand the phenotypic spectrum of KMT2B-related disorders and show that some individuals can have severe developmental delay without dystonia at least until mid-childhood. Additionally, we describe a recessive histone lysine-methylation defect caused by homozygous or compound heterozygous KDM5B variants and resulting in a recognizable syndrome with developmental delay, facial dysmorphism, and camptodactyly. Collectively, these results emphasize the significance of histone lysine methylation in normal human development and the importance of this process in human developmental disorders. Our results demonstrate that systematic clinically oriented pathway-based analysis of genomic data can accelerate the discovery of rare genetic disorders.

The effects of blueberry anthocyanins on histone acetylation in rat liver fibrosis

To determine the effects ofanthocyanins from blueberries on hepatic stellate cell (HSCs-T6) and on histone acetylation during liver fibrosis induced by CCl4 in rats. Fifty male SD rats weighing 180 ± 20g were randomly placed into a control group, a hepatic fibrosis group, a blueberry treatment group, a blueberry intervention group, and a natural recovery group. After the rats were sacrificed, the livers and the liver indexes were measured, and the pathological changes were observed by HE staining and Masson staining. The blood was analyzed for the four indexes of liver fibrosis and liver function; nucleoprotein from liver tissues and karyoplasm were isolated to determine the expression of acH3K9, acH3K14, and acH3K18 by Western blotting. Compared with the lethal rate of the control group, the median lethal rate of HSCs-T6 cells treated with a the 50μmol/L concentration was 66.94% (P < 0.05). The protein expression on α-SMA, type I collagen, TIMP1 significantly decreased (P < 0.05) following treatment with 50 ug/ml of anthocyanin for 36 h; moreover, the expression of acH3K9, acH3K14 and acH3K18 modification were up-regulated (P < 0.05). Furthermore, compared with the liver in the model group, the liver in the intervention group showed the most obvious improvement (P < 0.01), and its karyoplasm had increased expression of acH3K9, acH3K14 and acH3K18 (P<0.01). Regulating histone acetylation could improve liver function and liver fibrosis indexes in rats with hepatic fibrosis. The mechanism might be related to certain genes that promote apoptosis, so as to inhibit the effect of anti hepatic fibrosis.

Histone lysine methylation and congenital heart disease: From bench to bedside (Review)

Histone post-translational modifications (PTM) as one of the key epigenetic regulatory mechanisms that plays critical role in various biological processes, including regulating chromatin structure dynamics and gene expression. Histone lysine methyltransferase contributes to the establishment and maintenance of differential histone methylation status, which can recognize histone methylated sites and build an association between these modifications and their downstream processes. Recently, it was found that abnormalities in the histone lysine methylation level or pattern may lead to the occurrence of many types of cardiovascular diseases, such as congenital heart disease (CHD). In order to provide new theoretical basis and targets for the treatment of CHD from the view of developmental biology and genetics, this review discusses and elaborates on the association between histone lysine methylation modifications and CHD.

Repair of DNA Double-Strand Breaks in Heterochromatin

DNA double-strand breaks (DSBs) are among the most damaging lesions in DNA, since, if not identified and repaired, they can lead to insertions, deletions or chromosomal rearrangements. DSBs can be in the form of simple or complex breaks, and may be repaired by one of a number of processes, the nature of which depends on the complexity of the break or the position of the break within the chromatin. In eukaryotic cells, nuclear DNA is maintained as either euchromatin (EC) which is loosely packed, or in a denser form, much of which is heterochromatin (HC). Due to the less accessible nature of the DNA in HC as compared to that in EC, repair of damage in HC is not as straightforward as repair in EC. Here we review the literature on how cells deal with DSBs in HC.

Histone H3 Methyltransferase Suv39h1 Prevents Myogenic Terminal Differentiation by Repressing MEF2 Activity in Muscle Cells

The myogenic regulatory factors (MRFs) and myocyte enhancer factor 2 (MEF2) transcription factors have been extensively studied as key transcription factors that regulate myogenic gene expression. However, few reports on the molecular mechanism that modulates chromatin remodeling during skeletal muscle differentiation are available. We reported here that the expression of the H3-K9 methyltransferase Suv39h1 was decreased during myoblast differentiation. Ectopic expression of Suv39h1 could inhibit myoblast differentiation, increasing H3-K9 methylation levels, whereas knockdown of Suv39h1 stimulated myoblast differentiation. Furthermore, Suv39h1 interacted with MEF2C directly and inhibited MEF2 transcription activity in a dose-dependent manner. Together, our studies revealed a molecular mechanism wherein Suv39h1 modulated myogenic gene expression and activation during skeletal muscle differentiation.

Continual removal of H3K9 promoter methylation by Jmjd2 demethylases is vital for ESC self-renewal and early development

Chromatin-associated proteins are essential for the specification and maintenance of cell identity. They exert these functions through modulating and maintaining transcriptional patterns. To elucidate the functions of the Jmjd2 family of H3K9/H3K36 histone demethylases, we generated conditional Jmjd2a/Kdm4a, Jmjd2b/Kdm4b and Jmjd2c/Kdm4c/Gasc1 single, double and triple knockout mouse embryonic stem cells (ESCs). We report that while individual Jmjd2 family members are dispensable for ESC maintenance and embryogenesis, combined deficiency for specifically Jmjd2a and Jmjd2c leads to early embryonic lethality and impaired ESC self-renewal, with spontaneous differentiation towards primitive endoderm under permissive culture conditions. We further show that Jmjd2a and Jmjd2c both localize to H3K4me3-positive promoters, where they have widespread and redundant roles in preventing accumulation of H3K9me3 and H3K36me3. Jmjd2 catalytic activity is required for ESC maintenance, and increased H3K9me3 levels in knockout ESCs compromise the expression of several Jmjd2a/c targets, including genes that are important for ESC self-renewal. Thus, continual removal of H3K9 promoter methylation by Jmjd2 demethylases represents a novel mechanism ensuring transcriptional competence and stability of the pluripotent cell identity.

AIRE expands: new roles in immune tolerance and beyond

More than 15 years ago, mutations in the autoimmune regulator (AIRE) gene were identified as the cause of autoimmune polyglandular syndrome type 1 (APS1). It is now clear that this transcription factor has a crucial role in promoting self-tolerance in the thymus by regulating the expression of a wide array of self-antigens that have the commonality of being tissue-restricted in their expression pattern in the periphery. In this Review, we highlight many of the recent advances in our understanding of the complex biology that is related to AIRE, with a particular focus on advances in genetics, molecular interactions and the effect of AIRE on thymic selection of regulatory T cells. Furthermore, we highlight new areas of biology that are potentially affected by this key regulator of immune tolerance.

Histone H3K4 trimethylation: dynamic interplay with pre-mRNA splicing

Histone H3 lysine 4 trimethylation (H3K4me3) is often stated as a mark of transcriptionally active promoters. However, closer study of the positioning of H3K4me3 shows the mark locating primarily after the first exon at the 5′ splice site and overlapping with a CpG island in mammalian cells. There are several enzyme complexes that are involved in the placement of the H3K4me3 mark, including multiple protein complexes containing SETD1A, SETD1B, and MLL1 enzymes (writers). CXXC1, which is associated with SETD1A and SETD1B, target these enzymes to unmethylated CpG islands. Lysine demethylases (KDM5 family members, erasers) demethylate H3K4me3. The H3K4me3 mark is recognized by several proteins (readers), including lysine acetyltransferase complexes, chromatin remodelers, and RNA bound proteins involved in pre-mRNA splicing. Interestingly, attenuation of H3K4me3 impacts pre-mRNA splicing, and inhibition of pre-mRNA splicing attenuates H3K4me3.

Histone methyltransferases and demethylases: regulators in balancing osteogenic and adipogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are characterized by their self-renewing capacity and differentiation potential into multiple tissues. Thus, management of the differentiation capacities of MSCs is important for MSC-based regenerative medicine, such as craniofacial bone regeneration, and in new treatments for metabolic bone diseases, such as osteoporosis. In recent years, histone modification has been a growing topic in the field of MSC lineage specification, in which the Su(var)3–9, enhancer-of-zeste, trithorax (SET) domain-containing family and the Jumonji C (JmjC) domain-containing family represent the major histone lysine methyltransferases (KMTs) and histone lysine demethylases (KDMs), respectively. In this review, we summarize the current understanding of the epigenetic mechanisms by which SET domain-containing KMTs and JmjC domain-containing KDMs balance the osteogenic and adipogenic differentiation of MSCs.

Histone methyltransferases: novel targets for tumor and developmental defects

Histone lysine methylation plays a critical role in epigenetic regulation of eukaryotes. To date, studies have shown that lysine residues of K4, K9, K27, K36 and K79 in histone H3 and K20 in histone H4 can be modified by histone methyltransferases (HMTs). Such histone methylation can specifically activate or repress the transcriptional activity to play a key role in gene expression/regulation and biological genetics. Importantly, abnormities of patterns or levels of histone methylation in higher eukaryotes may result in tumorigenesis and developmental defects, suggesting histone methylation will be one of the important targets or markers for treating these diseases. This review will outline the structural characteristics, active sites and specificity of HMTs, correlation between histone methylation and human diseases and lay special emphasis on the progress of the research on H3K36 methylation.

A Phosphotyrosine Switch Controls the Association of Histone Mark Readers with Methylated Proteins

Although histone post-translational modifications play a paramount role in controlling access to genetic information, our understanding of the precise mechanisms regulating chromatin signaling remains superficial. For instance, histone H3 trimethylated on lysine 9 (H3K9(me3)) favors the association of chromodomain proteins such as heterochromatin protein 1α (HP1α) with chromatin. However, HP1α and other such chromatin proteins are not covering all specific histone marks at all times. Thus, how are these reader-histone interactions regulated? We propose tyrosine phosphorylation within the aromatic cage of histone mark readers as a molecular switch that can either turn ON or OFF and even alter the specificity of reader-histone interactions. We have identified tyrosine phosphorylation events on the chromatin proteins HP1α and M-phase phosphoprotein 8 that regulate their association with methylated histones in vitro (synthetic peptides, calf thymus purified histones, and nucleosomes), but also in cells, thus controlling access to genetic information.

Binding of 14-3-3 reader proteins to phosphorylated DNMT1 facilitates aberrant DNA methylation and gene expression

Mammalian DNA (cytosine-5) methyltransferase 1 (DNMT1) is essential for maintenance methylation. Phosphorylation of Ser143 (pSer143) stabilizes DNMT1 during DNA replication. Here, we show 14-3-3 is a reader protein of DNMT1pSer143. In mammalian cells 14-3-3 colocalizes and binds DNMT1pSer143 post-DNA replication. The level of DNMT1pSer143 increased with overexpression of 14-3-3 and decreased by its depletion. Binding of 14-3-3 proteins with DNMT1pSer143 resulted in inhibition of DNA methylation activity in vitro. In addition, overexpression of 14-3-3 in NIH3T3 cells led to decrease in DNMT1 specific activity resulting in hypomethylation of the genome that was rescued by transfection of DNMT1. Genes representing cell migration, mobility, proliferation and focal adhesion pathway were hypomethylated and overexpressed. Furthermore, overexpression of 14-3-3 also resulted in enhanced cell invasion. Analysis of TCGA breast cancer patient data showed significant correlation for DNA hypomethylation and reduced patient survival with increased 14-3-3 expressions. Therefore, we suggest that 14-3-3 is a crucial reader of DNMT1pSer143 that regulates DNA methylation and altered gene expression that contributes to cell invasion.

HBx relieves chromatin-mediated transcriptional repression of hepatitis B viral cccDNA involving SETDB1 histone methyltransferase

BACKGROUND & AIMS

Maintenance of the covalently closed circular HBV DNA (cccDNA) that serves as a template for HBV transcription is responsible for the failure of antiviral therapies. While studies in chronic hepatitis patients have shown that high viremia correlates with hyperacetylation of cccDNA-associated histones, the molecular mechanisms controlling cccDNA stability and transcriptional regulation are still poorly understood. This study aimed to decipher the role of chromatin and chromatin modifier proteins on HBV transcription.

METHODS

We analyzed the chromatin structure of actively transcribed or silenced cccDNA by infecting primary human hepatocytes and differentiated HepaRG cells with wild-type virus or virus deficient (HBVX-) for the expression of hepatitis B virus X protein (HBx), that is required for HBV expression.

RESULTS

In the absence of HBx, HBV cccDNA was transcriptionally silenced with the concomitant decrease of histone 3 (H3) acetylation and H3K4me3, increase of H3 di- and tri-methylation (H3K9me) and the recruitment of heterochromatin protein 1 factors (HP1) that correlate with condensed chromatin. SETDB1 was found to be the main histone methyltransferase responsible for the deposition of H3K9me3 and HBV repression. Finally, full transcriptional reactivation of HBVX- upon HBx re-expression correlated with an increase of histone acetylation and H3K4me3, and a concomitant decrease of HP1 binding and of H3K9me3 on the cccDNA.

CONCLUSION

Upon HBV infection, cellular mechanisms involving SETDB1-mediated H3K9me3 and HP1 induce silencing of HBV cccDNA transcription through modulation of chromatin structure. HBx is able to relieve this repression and allow the establishment of active chromatin.

Exposure to coplanar PCBs induces endothelial cell inflammation through epigenetic regulation of NF-κB subunit p65

Epigenetic modifications of DNA and histones alter cellular phenotypes without changing genetic codes. Alterations of epigenetic marks can be induced by exposure to environmental pollutants and may contribute to associated disease risks. Here we test the hypothesis that endothelial cell dysfunction induced by exposure to polychlorinated biphenyls (PCBs) is mediated in part though histone modifications. In this study, human vascular endothelial cells were exposed to physiologically relevant concentrations of several PCBs congeners (e.g., PCBs 77, 118, 126 and 153) followed by quantification of inflammatory gene expression and changes of histone methylation. Only exposure to coplanar PCBs 77 and 126 induced the expression of histone H3K9 trimethyl demethylase jumonji domain-containing protein 2B (JMJD2B) and nuclear factor-kappa B (NF-κB) subunit p65, activated NF-κB signaling as evidenced by nuclear translocation of p65, and up-regulated p65 target inflammatory genes, such as interleukin (IL)-6, C-reactive protein (CRP), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and IL-1α/β. The increased accumulation of JMJD2B in the p65 promoter led to a depletion of H3K9me3 repression mark, which accounts for the observed up-regulation of p65 and associated inflammatory genes. JMJD2B gene knockdown confirmed a critical role for this histone demethylase in mediating PCB-induced inflammation of the vascular endothelium. Finally, it was determined, via chemical inhibition, that PCB-induced up-regulation of JMJD2B was estrogen receptor-alpha (ER-α) dependent. These data suggest that coplanar PCBs may exert endothelial cell toxicity through changes in histone modifications.

Methionine-dependent histone methylation at developmentally important gene loci in mouse preimplantation embryos

The involvement of specific nutrients in epigenetic gene regulation is a possible mechanism underlying nutrition-directed phenotypic alteration. However, the involvement of nutrients in gene-specific epigenetic regulation remains poorly understood. Methionine has been received attention as a possible nutrient involved in epigenetic modifications, as it is a precursor of the universal methyl donor for epigenetic methylation of DNA and histones. In the present study, the disruption of methionine metabolism by ethionine, an antimetabolite of methionine, induced abnormally higher expression of genes related to cell lineage differentiation and resulted in impaired blastocyst development of mouse preimplantation embryos in vitro. These effects were mitigated by the presence of methionine. Importantly, ethionine treatment induced lower trimethylation of histone H3 lysine 9 but did not affect methylation of DNA in the promoter regions of the examined genes. These results demonstrated that intact methionine metabolism is required for proper epigenetic histone modifications and normal expression of developmentally important genes during preimplantation development.

Evolution and conservation of JmjC domain proteins in the green lineage

Histone modification regulates plant development events by epigenetically silencing or activating gene expression, and histone methylation is regulated by histone lysine methyltransferases (KMTs) and histone lysine demethylases (KDMs). The JmjC domain proteins, an important KDM family, erase methyl marks (CH3-) from histones and play key roles in maintaining homeostasis of histone methylation in vivo. Here, we analyzed 169 JmjC domain proteins from whole genomes of plants ranging from green alga to higher plants together with 36 from two animals (fruit fly and human). The plant JmjC domain proteins were divided into seven groups. Group-I KDM4/JHDM3 and Group-V JMJD6 were found in all the plant species and the other groups were detected mainly in vascular or seed plants. Group-I KDM4/JHDM3 was potentially associated with demethylation of H3K9me2/3, H3K27me2/3, and H3K36me1/2/3, Group-II KDM5A with H3K4me1/2/3, Group-III KDM5B with H3K4me1/2/3 and H3K9me1/2/3, Group-V JMJD6 with H3R2, H4R3, and hydroxylation of H4, and Group-VII KDM3/JHDM2 with H3K9me1/2/3. Group-IV/Group-VI JmjC domain-only A/B proteins were involved in hydroxylation and demethylation of unknown substrate sites. The binding sites for the cofactors Fe(II) and α-ketoglutarate in the JmjC domains also were analyzed. In the α-ketoglutarate binding sites, Thr/Phe/Ser and Lys were conserved and in the Fe(II) binding sites, two His and Glu/Asp were conserved. The results show that JmjC domain proteins are a conserved family in which domain organization and cofactor binding sites have been modified in some species. Our results provide insights into KDM evolution and lay a foundation for functional characterization of KDMs.

Advances in the development of histone lysine demethylase inhibitors

The covalent modification of histones is closely associated with regulation of gene transcription. Chromatin modifications have been suggested to represent an epigenetic code that is dynamically 'written' and 'erased' by specialized proteins, and 'read', or interpreted, by proteins that translate the code into gene expression changes. Initially thought to be an irreversible process, histone methylation is now known to be reversed by demethylases, FAD dependent amineoxidases and by iron(II)-alpha-ketoglutarate dependent deoxygenases of the Jumonji family. Altered histone demethylase activities have been associated with human disease, including cancer. The first wave of novel investigational drugs directed against KDM1A has recently entered the clinic, and the first specific inhibitor targeting a Jumonji KDM is advancing in preclinical regulatory studies.

Histone modifications: Targeting head and neck cancer stem cells

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, and is responsible for a quarter of a million deaths annually. The survival rate for HNSCC patients is poor, showing only minor improvement in the last three decades. Despite new surgical techniques and chemotherapy protocols, tumor resistance to chemotherapy remains a significant challenge for HNSCC patients. Numerous mechanisms underlie chemoresistance, including genetic and epigenetic alterations in cancer cells that may be acquired during treatment and activation of mitogenic signaling pathways, such as nuclear factor kappa-light-chain-enhancer-of activated B cell, that cause reduced apoptosis. In addition to dysfunctional molecular signaling, emerging evidence reveals involvement of cancer stem cells (CSCs) in tumor development and in tumor resistance to chemotherapy and radiotherapy. These observations have sparked interest in understanding the mechanisms involved in the control of CSC function and fate. Post-translational modifications of histones dynamically influence gene expression independent of alterations to the DNA sequence. Recent findings from our group have shown that pharmacological induction of post-translational modifications of tumor histones dynamically modulates CSC plasticity. These findings suggest that a better understanding of the biology of CSCs in response to epigenetic switches and pharmacological inhibitors of histone function may directly translate to the development of a mechanism-based strategy to disrupt CSCs. In this review, we present and discuss current knowledge on epigenetic modifications of HNSCC and CSC response to DNA methylation and histone modifications. In addition, we discuss chromatin modifications and their role in tumor resistance to therapy.

MMSET: role and therapeutic opportunities in multiple myeloma

Recurrent chromosomal translocations are central to the pathogenesis, diagnosis, and prognosis of hematologic malignancies. The translocation t(4; 14)(p16; q32) is one of the most common translocations in multiple myeloma (MM) and is associated with very poor prognosis. The t(4; 14) translocation leads to the simultaneous overexpression of two genes, FGFR3 (fibroblast growth factor receptor 3) and MMSET (multiple myeloma SET domain), both of which have potential oncogenic activity. However, approximately 30% of t(4; 14) MM patients do not express FGFR3 and have poor prognosis irrespective of FGFR3 expression, whereas MMSET overexpression is universal in t(4; 14) cases. In this review, we provide an overview of recent findings regarding the oncogenic roles of MMSET in MM and its functions on histone methylation. We also highlight some of MMSET partners and its downstream signalling pathways and discuss the potential therapeutics targeting MMSET.

Histones and long non-coding RNAs: the new insights of epigenetic deregulation involved in oral cancer

Oral squamous cell carcinoma (OSCC) is a category of aggressive malignancies that represent clinically, molecularly, and etiologically heterogeneous tumors. The majority of OSCCs are associated with tobacco and alcohol use, acting both independently and synergistically, which suggests that the environment plays an important role in carcinogenesis; however, the mechanisms associated with the development of OSCC are not well understood. It has been proposed that the epigenetic components could be implicated in the initiation and progression of OSCC. Primarily, aberrant DNA methylation patterns have been widely addressed in the study of OSCC. Diverse studies have proposed that other epigenetic processes such as post-translational histone modification, the deposition of histone variants, histone chaperones, and recently non-coding RNA, can be also involved in the development of oral cancer. In this review we focus on describing the new insights of the epigenetics processes that are related with OSCC as histones variants and long non-coding RNAs.