Histone demethylase LSD2 acts as an E3 ubiquitin ligase and inhibits cancer cell growth through promoting proteasomal degradation of OGT

Epigenetic code underlying EGFR-TKI resistance in non-small cell lung cancer: Elucidation of mechanisms and perspectives on therapeutic strategies

Non-small-cell lung cancer (NSCLC) is the most common lung cancer subtype, and epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the core drugs used for its treatment. However, the emergence of drug resistance poses a significant challenge to their clinical efficacy. As a significant role-player in cancer development and maintenance, histone modifications, DNA methylation and noncoding RNA (ncRNA) changes have been proven to play a crucial part in driving EGFR-TKI resistance, which provides promising potential therapeutic targets and biomarkers for overcoming drug resistance. This review delves into the complex epigenetic mechanisms that cause EGFR-TKI resistance and emphasizes the potential of combined epigenetic therapies, aiming to provide better-targeted treatment options for NSCLC patients with NSCLC and drive innovative strategies to overcome the challenges of drug resistance.

FBXO31-mediated ubiquitination of OGT maintains O-GlcNAcylation homeostasis to restrain endometrial malignancy

Protein O-GlcNAcylation is a post-translational modification coupled to cellular metabolic plasticity. Aberrant O-GlcNAcylation has been observed in many cancers including endometrial cancer (EC), a common malignancy in women. However, clinical characterization of dysregulated O-GlcNAcylation homeostasis in EC and interrogating its molecular mechanism remain incomplete. Here we report that O-GlcNAcylation level is positively correlated with EC histologic grade in a Chinese cohort containing 219 tumors, validated in The Cancer Genome Atlas dataset. Increasing O-GlcNAcylation in patient-derived endometrial epithelial organoids promotes proliferation and stem-like cell properties, whereas decreasing O-GlcNAcylation limits the growth of endometrial cancer organoids. CRISPR screen and biochemical characterization reveal that tumor suppressor F-box only protein 31 (FBXO31) regulates O-GlcNAcylation homeostasis in EC by ubiquitinating the O-GlcNAc transferase OGT. Downregulation of O-GlcNAcylation impedes EC tumor formation in mouse models. Collectively, our study highlights O-GlcNAcylation as a useful stratification marker and a therapeutic vulnerability for the advanced, poorly differentiated EC cases.

CARM1-mediated OGT arginine methylation promotes non-small cell lung cancer glycolysis by stabilizing OGT

O-GlcNAcylation catalyzed by O-GlcNAc transferase (OGT) plays an important role in the regulation of tumor glycolysis. However, the mechanism underlying OGT regulation remains largely unknown. Here, we showed that coactivator associated arginine methyltransferase 1 (CARM1) sensed changes of extracellular glucose levels in non-small cell lung cancer (NSCLC) cells. Increased glucose upregulated CARM1 and OGT. CARM1 methylated OGT at arginine 348, promoting its stability through binding of the deubiquitinase USP9X. The arginine methylation of OGT increased global O-GlcNAcylation levels, thereby promoting glycolysis in NSCLC cells. OGT arginine methylation also upregulated c-Myc expression and promoted the proliferation of NSCLC cells in vitro and in vivo. Consistently, OGT expression was positively correlated with CARM1 in human NSCLC samples. The present findings shed light on the mechanism underlying the stabilization of OGT by arginine methylation in response to changes of glucose concentration. The study also clarified the role of the CARM1-USP9X-OGT axis in glycolysis in NSCLC, providing a potential new target or therapeutic strategy in NSCLC.

Opportunities for Therapeutic Modulation of O-GlcNAc

O-Linked β-N-acetylglucosamine (O-GlcNAc) is an essential, dynamic monosaccharide post-translational modification (PTM) found on serine and threonine residues of thousands of nucleocytoplasmic proteins. The installation and removal of O-GlcNAc is controlled by a single pair of enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. Since its discovery four decades ago, O-GlcNAc has been found on diverse classes of proteins, playing important functional roles in many cellular processes. Dysregulation of O-GlcNAc homeostasis has been implicated in the pathogenesis of disease, including neurodegeneration, X-linked intellectual disability (XLID), cancer, diabetes, and immunological disorders. These foundational studies of O-GlcNAc in disease biology have motivated efforts to target O-GlcNAc therapeutically, with multiple clinical candidates under evaluation. In this review, we describe the characterization and biochemistry of OGT and OGA, cellular O-GlcNAc regulation, development of OGT and OGA inhibitors, O-GlcNAc in pathophysiology, clinical progress of O-GlcNAc modulators, and emerging opportunities for targeting O-GlcNAc. This comprehensive resource should motivate further study into O-GlcNAc function and inspire strategies for therapeutic modulation of O-GlcNAc.

14-3-3ε augments OGT stability by binding with S20-phosphorylated OGT

The relationship between O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) and mitosis is intertwined. Besides the numerous mitotic OGT substrates that have been identified, OGT itself is also a target of the mitotic machinery. Previously, our investigations have shown that Checkpoint kinase 1 (Chk1) phosphorylates OGT at Ser-20 to increase OGT levels during cytokinesis, suggesting that OGT levels oscillate as mitosis progresses. Herein we studied its underlying mechanism. We set out from an R17C mutation of OGT, which is a uterine carcinoma mutation in The Cancer Genome Atlas. We found that R17C abolishes the S20 phosphorylation of OGT, as it lies in the Chk1 phosphorylating consensus motif. Consistent with our previous report that pSer-20 is essential for OGT level increases during cytokinesis, we further demonstrate that the R17C mutation renders OGT less stable, decreases vimentin phosphorylation levels and results in cytokinesis defects. Based on bioinformatic predictions, pSer-20 renders OGT more likely to interact with 14-3-3 proteins, the phospho-binding signal adaptor/scaffold protein family. By screening the seven isoforms of 14-3-3 family, we show that 14-3-3ε specifically associates with Ser-20-phosphorylated OGT. Moreover, we studied the R17C and S20A mutations in xenograft models and demonstrated that they both inhibit uterine carcinoma compared to wild-type OGT, probably due to less cellular reproduction. Our work is a sequel of our previous report on pS20 of OGT and is in line with the notion that OGT is intricately regulated by the mitotic network.

Navigating the complexity of Polycomb repression: Enzymatic cores and regulatory modules

Polycomb proteins are a fundamental repressive system that plays crucial developmental roles by orchestrating cell-type-specific transcription programs that govern cell identity. Direct alterations of Polycomb activity are indeed implicated in human pathologies, including developmental disorders and cancer. General Polycomb repression is coordinated by three distinct activities that regulate the deposition of two histone post-translational modifications: tri-methylation of histone H3 lysine 27 (H3K27me3) and histone H2A at lysine 119 (H2AK119ub1). These activities exist in large and heterogeneous multiprotein ensembles consisting of common enzymatic cores regulated by heterogeneous non-catalytic modules composed of a large number of accessory proteins with diverse biochemical properties. Here, we have analyzed the current molecular knowledge, focusing on the functional interaction between the core enzymatic activities and their regulation mediated by distinct accessory modules. This provides a comprehensive analysis of the molecular details that control the establishment and maintenance of Polycomb repression, examining their underlying coordination and highlighting missing information and emerging new features of Polycomb-mediated transcriptional control.

O-GlcNAcylation of RBM14 contributes to elevated cellular O-GlcNAc through regulation of OGA protein stability

Dysregulation of O-GlcNAcylation has emerged as a potential biomarker for several diseases, particularly cancer. The role of OGT (O-GlcNAc transferase) in maintaining O-GlcNAc homeostasis has been extensively studied; nevertheless, the regulation of OGA (O-GlcNAcase) in cancer remains elusive. Here, we demonstrated that the multifunctional protein RBM14 is a regulator of cellular O-GlcNAcylation. By investigating the correlation between elevated O-GlcNAcylation and increased RBM14 expression in lung cancer cells, we discovered that RBM14 promotes ubiquitin-dependent proteasomal degradation of OGA, ultimately mediating cellular O-GlcNAcylation levels. In addition, RBM14 itself is O-GlcNAcylated at serine 521, regulating its interaction with the E3 ligase TRIM33, consequently affecting OGA protein stability. Moreover, we demonstrated that mutation of serine 521 to alanine abrogated the oncogenic properties of RBM14. Collectively, our findings reveal a previously unknown mechanism for the regulation of OGA and suggest a potential therapeutic target for the treatment of cancers with dysregulated O-GlcNAcylation.

LSD2 Is an Epigenetic Player in Multiple Types of Cancer and Beyond

Histone demethylases, enzymes responsible for removing methyl groups from histone proteins, have emerged as critical players in regulating gene expression and chromatin dynamics, thereby influencing various cellular processes. LSD2 and LSD1 have attracted considerable interest among these demethylases because of their associations with cancer. However, while LSD1 has received significant attention, LSD2 has not been recognized to the same extent. In this study, we conduct a comprehensive comparison between LSD2 and LSD1, with a focus on exploring LSD2's implications. While both share structural similarities, LSD2 possesses unique features as well. Functionally, LSD2 shows diverse roles, particularly in cancer, with tissue-dependent roles. Additionally, LSD2 extends beyond histone demethylation, impacting DNA methylation, cancer cell reprogramming, E3 ubiquitin ligase activity and DNA damage repair pathways. This study underscores the distinct roles of LSD2, providing insights into their contributions to cancer and other cellular processes.

Current knowledge and potential intervention of hexosamine biosynthesis pathway in lung cancer

Lung cancer is a highly prevalent malignancy characterized by significant metabolic alterations. Understanding the metabolic rewiring in lung cancer is crucial for the development of effective therapeutic strategies. The hexosamine biosynthesis pathway (HBP) is a metabolic pathway that plays a vital role in cellular metabolism and has been implicated in various cancers, including lung cancer. Abnormal activation of HBP is involved in the proliferation, progression, metastasis, and drug resistance of tumor cells. In this review, we will discuss the function and regulation of metabolic enzymes related to HBP in lung cancer. Furthermore, the implications of targeting the HBP for lung cancer treatment are also discussed, along with the challenges and future directions in this field. This review provides a comprehensive understanding of the role and intervention of HBP in lung cancer. Future research focusing on the HBP in lung cancer is essential to uncover novel treatment strategies and improve patient outcomes.

O-GlcNAcylation in cancer development and immunotherapy

O-linked β-D-N-acetylglucosamine (O-GlcNAc), as a posttranslational modification (PTM), is a reversible reaction that attaches β-N-GlcNAc to Ser/Thr residues on specific proteins by O-GlcNAc transferase (OGT). O-GlcNAcase (OGA) removes the O-GlcNAc from O-GlcNAcylated proteins. O-GlcNAcylation regulates numerous cellular processes, including signal transduction, the cell cycle, metabolism, and energy homeostasis. Dysregulation of O-GlcNAcylation contributes to the development of various diseases, including cancers. Accumulating evidence has revealed that higher expression levels of OGT and hyper-O-GlcNAcylation are detected in many cancer types and governs glucose metabolism, proliferation, metastasis, invasion, angiogenesis, migration and drug resistance. In this review, we describe the biological functions and molecular mechanisms of OGT- or O-GlcNAcylation-mediated tumorigenesis. Moreover, we discuss the potential role of O-GlcNAcylation in tumor immunotherapy. Furthermore, we highlight that compounds can target O-GlcNAcylation by regulating OGT to suppress oncogenesis. Taken together, targeting protein O-GlcNAcylation might be a promising strategy for the treatment of human malignancies.

Cellular differentiation into hyphae and spores in halophilic archaea

Several groups of bacteria have complex life cycles involving cellular differentiation and multicellular structures. For example, actinobacteria of the genus Streptomyces form multicellular vegetative hyphae, aerial hyphae, and spores. However, similar life cycles have not yet been described for archaea. Here, we show that several haloarchaea of the family Halobacteriaceae display a life cycle resembling that of Streptomyces bacteria. Strain YIM 93972 (isolated from a salt marsh) undergoes cellular differentiation into mycelia and spores. Other closely related strains are also able to form mycelia, and comparative genomic analyses point to gene signatures (apparent gain or loss of certain genes) that are shared by members of this clade within the Halobacteriaceae. Genomic, transcriptomic and proteomic analyses of non-differentiating mutants suggest that a Cdc48-family ATPase might be involved in cellular differentiation in strain YIM 93972. Additionally, a gene encoding a putative oligopeptide transporter from YIM 93972 can restore the ability to form hyphae in a Streptomyces coelicolor mutant that carries a deletion in a homologous gene cluster (bldKA-bldKE), suggesting functional equivalence. We propose strain YIM 93972 as representative of a new species in a new genus within the family Halobacteriaceae, for which the name Actinoarchaeum halophilum gen. nov., sp. nov. is herewith proposed. Our demonstration of a complex life cycle in a group of haloarchaea adds a new dimension to our understanding of the biological diversity and environmental adaptation of archaea.

Hepatocyte Kctd17 Inhibition Ameliorates Glucose Intolerance and Hepatic Steatosis Caused by Obesity-induced Chrebp Stabilization

BACKGROUND & AIMS

Obesity predisposes to type 2 diabetes (T2D) and nonalcoholic fatty liver disease (NAFLD), but underlying mechanisms are incompletely understood. Potassium channel tetramerization domain-containing protein 17 (Kctd17) levels are increased in livers from obese mice and humans. In this study, we investigated the mechanism of increased Kctd17 and whether it is causal to obesity-induced metabolic complications.

METHODS

We transduced Rosa26-LSL-Cas9 knockin mice with AAV8-TBG-Cre (Control), AAV8-U6-Kctd17 sgRNA-TBG-Cre (L-Kctd17), AAV8-U6-Oga sgRNA-TBG-Cre (L-Oga), or AAV8-U6-Kctd17/Oga sgRNA-TBG-Cre (DKO). We fed mice a high-fat diet (HFD) and assessed for hepatic glucose and lipid homeostasis. We generated Kctd17, O-GlcNAcase (Oga), or Kctd17/Oga-knockout hepatoma cells by CRISPR-Cas9, and Kctd17-directed antisense oligonucleotide to test therapeutic potential in vivo. We analyzed transcriptomic data from patients with NAFLD.

RESULTS

Hepatocyte Kctd17 expression was increased in HFD-fed mice due to increased Srebp1c activity. HFD-fed L-Kctd17 or Kctd17 antisense oligonucleotide-treated mice show improved glucose tolerance and hepatic steatosis, whereas forced Kctd17 expression caused glucose intolerance and hepatic steatosis even in lean mice. Kctd17 induced Oga degradation, resulting in increasing carbohydrate response element-binding protein (Chrebp) protein, so concomitant Oga knockout negated metabolic benefits of hepatocyte Kctd17 deletion. In patients with NAFLD, KCTD17 messenger RNA was positively correlated with expression of Chrebp target and other lipogenic genes.

CONCLUSIONS

Srebp1c-induced hepatocyte Kctd17 expression in obesity disrupted glucose and lipid metabolism by stabilizing Chrebp, and may represent a novel therapeutic target for obesity-induced T2D and NAFLD.

Targeting epigenetic regulators to overcome drug resistance in cancers

Drug resistance is mainly responsible for cancer recurrence and poor prognosis. Epigenetic regulation is a heritable change in gene expressions independent of nucleotide sequence changes. As the common epigenetic regulation mechanisms, DNA methylation, histone modification, and non-coding RNA regulation have been well studied. Increasing evidence has shown that aberrant epigenetic regulations contribute to tumor resistance. Therefore, targeting epigenetic regulators represents an effective strategy to reverse drug resistance. In this review, we mainly summarize the roles of epigenetic regulation in tumor resistance. In addition, as the essential factors for epigenetic modifications, histone demethylases mediate the histone or genomic DNA modifications. Herein, we comprehensively describe the functions of the histone demethylase family including the lysine-specific demethylase family, the Jumonji C-domain-containing demethylase family, and the histone arginine demethylase family, and fully discuss their regulatory mechanisms related to cancer drug resistance. In addition, therapeutic strategies, including small-molecule inhibitors and small interfering RNA targeting histone demethylases to overcome drug resistance, are also described.

Structural and Functional Landscape of FAD-Dependent Histone Lysine Demethylases for New Drug Discovery

Small molecules targeting the flavin adenine dinucleotide (FAD)-dependent histone lysine demethylase LSD family have displayed therapeutic promise against various diseases. Nine clinical candidates targeting the classic demethylase-dependent functions of the LSD family are currently being investigated for treating cancers, neurodegenerative diseases, etc. Moreover, targeting noncatalytic functions of LSDs also represents an emerging strategy for treating human diseases. In this Perspective, we provide full structural and functional landscape of the LSD family and action modes of different types of LSD inhibitors including natural products, peptides, and synthetic compounds, aiming to reveal new druggable space for the design of new LSD inhibitors. Particularly, we first classify these inhibitors into three types based on their unique binding modes. Additionally, the strategies targeting the demethylase-independent functions of LSDs are also briefly discussed. This Perspective may benefit the discovery of new LSD inhibitors for probing LSD biology and/or treating human diseases.

Relationship between histone demethylase LSD family and development and prognosis of gastric cancer

Objective

to elucidate the correlation between histone demethylase and gastric cancer.

Research object

histone demethylase and gastric cancer.

Results

As one of the important regulatory mechanisms in molecular biology and epigenetics, histone modification plays an important role in gastric cancer including downstream gene expression regulation and epigenetics effect. Both histone methyltransferase and histone demethylases are involved in the formation and maintaining different of histone methylation status, which in turn through a variety of vital molecules and signaling pathways involved in the recognition of histone methylation modification caused by the downstream biological process, eventually participate in the regulation of chromatin function, and with a variety of important physiological activities, especially closely related to the occurrence of gastric cancer and embryonic development.

Conclusion

This paper intends to review the research progress in this field from the aspects of histone methylation modification and the protein structure, catalytic mechanism and biological function of the important histone demethylases LSD1 and LSD2, in order to provide the theoretical reference for further understanding and exploration of histone demethylases in development and prognosis of gastric cancer.

Targeting the LSD1/KDM1 Family of Lysine Demethylases in Cancer and Other Human Diseases

Lysine-specific demethylase 1 (LSD1) was the first histone demethylase discovered and the founding member of the flavin-dependent lysine demethylase family (KDM1). The human KDM1 family includes KDM1A and KDM1B, which primarily catalyze demethylation of histone H3K4me1/2. The KDM1 family is involved in epigenetic gene regulation and plays important roles in various biological and disease pathogenesis processes, including cell differentiation, embryonic development, hormone signaling, and carcinogenesis. Malfunction of many epigenetic regulators results in complex human diseases, including cancers. Regulators such as KDM1 have become potential therapeutic targets because of the reversibility of epigenetic control of genome function. Indeed, several classes of KDM1-selective small molecule inhibitors have been developed, some of which are currently in clinical trials to treat various cancers. In this chapter, we review the discovery, biochemical, and molecular mechanisms, atomic structure, genetics, biology, and pathology of the KDM1 family of lysine demethylases. Focusing on cancer, we also provide a comprehensive summary of recently developed KDM1 inhibitors and related preclinical and clinical studies to provide a better understanding of the mechanisms of action and applications of these KDM1-specific inhibitors in therapeutic treatment.

The Emerging Roles of Protein Interactions with O-GlcNAc Cycling Enzymes in Cancer

The dynamic O-GlcNAc modification of intracellular proteins is an important nutrient sensor for integrating metabolic signals into vast networks of highly coordinated cellular activities. Dysregulation of the sole enzymes responsible for O-GlcNAc cycling, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), and the associated cellular O-GlcNAc profile is a common feature across nearly every cancer type. Many studies have investigated the effects of aberrant OGT/OGA expression on global O-GlcNAcylation activity in cancer cells. However, recent studies have begun to elucidate the roles of protein-protein interactions (PPIs), potentially through regions outside of the immediate catalytic site of OGT/OGA, that regulate greater protein networks to facilitate substrate-specific modification, protein translocalization, and the assembly of larger biomolecular complexes. Perturbation of OGT/OGA PPI networks makes profound changes in the cell and may directly contribute to cancer malignancies. Herein, we highlight recent studies on the structural features of OGT and OGA, as well as the emerging roles and molecular mechanisms of their aberrant PPIs in rewiring cancer networks. By integrating complementary approaches, the research in this area will aid in the identification of key protein contacts and functional modules derived from OGT/OGA that drive oncogenesis and will illuminate new directions for anti-cancer drug development.

Nutrient-sensitive protein O-GlcNAcylation shapes daily biological rhythms

O-linked-N-acetylglucosaminylation (O-GlcNAcylation) is a nutrient-sensitive protein modification that alters the structure and function of a wide range of proteins involved in diverse cellular processes. Similar to phosphorylation, another protein modification that targets serine and threonine residues, O-GlcNAcylation occupancy on cellular proteins exhibits daily rhythmicity and has been shown to play critical roles in regulating daily rhythms in biology by modifying circadian clock proteins and downstream effectors. We recently reported that daily rhythm in global O-GlcNAcylation observed in Drosophila tissues is regulated via the integration of circadian and metabolic signals. Significantly, mistimed feeding, which disrupts coordination of these signals, is sufficient to dampen daily O-GlcNAcylation rhythm and is predicted to negatively impact animal biological rhythms and health span. In this review, we provide an overview of published and potential mechanisms by which metabolic and circadian signals regulate hexosamine biosynthetic pathway metabolites and enzymes, as well as O-GlcNAc processing enzymes to shape daily O-GlcNAcylation rhythms. We also discuss the significance of functional interactions between O-GlcNAcylation and other post-translational modifications in regulating biological rhythms. Finally, we highlight organ/tissue-specific cellular processes and molecular pathways that could be modulated by rhythmic O-GlcNAcylation to regulate time-of-day-specific biology.

O-GlcNAcylation links oncogenic signals and cancer epigenetics

Prevalent dysregulation of epigenetic modifications plays a pivotal role in cancer. Targeting epigenetic abnormality is a new strategy for cancer therapy. Understanding how conventional oncogenic factors cause epigenetic abnormality is of great basic and translational value. O-GlcNAcylation is a protein modification which affects physiology and pathophysiology. In mammals, O-GlcNAcylation is catalyzed by one single enzyme OGT and removed by one single enzyme OGA. O-GlcNAcylation is affected by the availability of the donor, UDP-GlcNAc, generated by the serial enzymatic reactions in the hexoamine biogenesis pathway (HBP). O-GlcNAcylation regulates a wide spectrum of substrates including many proteins involved in epigenetic modification. Like epigenetic modifications, abnormality of O-GlcNAcylation is also common in cancer. Studies have revealed substantial impact on HBP enzymes and OGT/OGA by oncogenic signals. In this review, we will first summarize how oncogenic signals regulate HBP enzymes, OGT and OGA in cancer. We will then integrate this knowledge with the up to date understanding how O-GlcNAcylation regulates epigenetic machinery. With this, we propose a signal axis from oncogenic signals through O-GlcNAcylation dysregulation to epigenetic abnormality in cancer. Further elucidation of this axis will not only advance our understanding of cancer biology but also provide new revenues towards cancer therapy.

Pathophysiological interplay between O-GlcNAc transferase and the Machado-Joseph disease protein ataxin-3

Aberrant O-GlcNAcylation, a protein posttranslational modification defined by the O-linked attachment of the monosaccharide N-acetylglucosamine (O-GlcNAc), has been implicated in neurodegenerative diseases. However, although many neuronal proteins are substrates for O-GlcNAcylation, this process has not been extensively investigated in polyglutamine disorders. We aimed to evaluate the enzyme O-GlcNAc transferase (OGT), which attaches O-GlcNAc to target proteins, in Machado-Joseph disease (MJD). MJD is a neurodegenerative condition characterized by ataxia and caused by the expansion of a polyglutamine stretch within the deubiquitinase ataxin-3, which then present increased propensity to aggregate. By analyzing MJD cell and animal models, we provide evidence that OGT is dysregulated in MJD, therefore compromising the O-GlcNAc cycle. Moreover, we demonstrate that wild-type ataxin-3 modulates OGT protein levels in a proteasome-dependent manner, and we present OGT as a substrate for ataxin-3. Targeting OGT levels and activity reduced ataxin-3 aggregates, improved protein clearance and cell viability, and alleviated motor impairment reminiscent of ataxia of MJD patients in zebrafish model of the disease. Taken together, our results point to a direct interaction between OGT and ataxin-3 in health and disease and propose the O-GlcNAc cycle as a promising target for the development of therapeutics in the yet incurable MJD.

Regulation of O-Linked N-Acetyl Glucosamine Transferase (OGT) through E6 Stimulation of the Ubiquitin Ligase Activity of E6AP

Glycosyltransferase OGT catalyzes the conjugation of O-linked β-D-N-acetylglucosamine (O-GlcNAc) to Ser and Thr residues of the cellular proteins and regulates many key processes in the cell. Here, we report the identification of OGT as a ubiquitination target of HECT-type E3 ubiquitin (UB) ligase E6AP, whose overexpression in HEK293 cells would induce the degradation of OGT. We also found that the expression of E6AP in HeLa cells with the endogenous expression of the E6 protein of the human papillomavirus (HPV) would accelerate OGT degradation by the proteasome and suppress O-GlcNAc modification of OGT substrates in the cell. Overall, our study establishes a new mechanism of OGT regulation by the ubiquitin-proteasome system (UPS) that mediates the crosstalk between protein ubiquitination and O-GlcNAcylation pathways underlying diverse cellular processes.

Histone demethylase KDM4A plays an oncogenic role in nasopharyngeal carcinoma by promoting cell migration and invasion

Compelling evidence has indicated the vital role of lysine-specific demethylase 4 A (KDM4A), hypoxia-inducible factor-1α (HIF1α) and the mechanistic target of rapamycin (mTOR) signaling pathway in nasopharyngeal carcinoma (NPC). Therefore, we aimed to investigate whether KDM4A affects NPC progression by regulating the HIF1α/DDIT4/mTOR signaling pathway. First, NPC and adjacent tissue samples were collected, and KDM4A protein expression was examined by immunohistochemistry. Then, the interactions among KDM4A, HIF1α and DDIT4 were assessed. Gain- and loss-of-function approaches were used to alter KDM4A, HIF1α and DDIT4 expression in NPC cells. The mechanism of KDM4A in NPC was evaluated both in vivo and in vitro via RT-qPCR, Western blot analysis, MTT assay, Transwell assay, flow cytometry and tumor formation experiments. KDM4A, HIF1α, and DDIT4 were highly expressed in NPC tissues and cells. Mechanistically, KDM4A inhibited the enrichment of histone H3 lysine 9 trimethylation (H3K9me3) in the HIF1α promoter region and thus inhibited the methylation of HIF1α to promote HIF1α expression, thus upregulating DDIT4 and activating the mTOR signaling pathway. Overexpression of KDM4A, HIF1α, or DDIT4 or activation of the mTOR signaling pathway promoted SUNE1 cell proliferation, migration, and invasion but inhibited apoptosis. KDM4A silencing blocked the mTOR signaling pathway by inhibiting the HIF1α/DDIT4 axis to inhibit the growth of SUNE1 cells in vivo. Collectively, KDM4A silencing could inhibit NPC progression by blocking the activation of the HIF1α/DDIT4/mTOR signaling pathway by increasing H3K9me3, highlighting a promising therapeutic target for NPC.

Histone demethylase AMX-1 is necessary for proper sensitivity to interstrand crosslink DNA damage

Histone methylation is dynamically regulated to shape the epigenome and adjust central nuclear processes including transcription, cell cycle control and DNA repair. Lysine-specific histone demethylase 2 (LSD2) has been implicated in multiple types of human cancers. However, its functions remain poorly understood. This study investigated the histone demethylase LSD2 homolog AMX-1 in C. elegans and uncovered a potential link between H3K4me2 modulation and DNA interstrand crosslink (ICL) repair. AMX-1 is a histone demethylase and mainly localizes to embryonic cells, the mitotic gut and sheath cells. Lack of AMX-1 expression resulted in embryonic lethality, a decreased brood size and disorganized premeiotic tip germline nuclei. Expression of AMX-1 and of the histone H3K4 demethylase SPR-5 is reciprocally up-regulated upon lack of each other and the mutants show increased H3K4me2 levels in the germline, indicating that AMX-1 and SPR-5 regulate H3K4me2 demethylation. Loss of AMX-1 function activates the CHK-1 kinase acting downstream of ATR and leads to the accumulation of RAD-51 foci and increased DNA damage-dependent apoptosis in the germline. AMX-1 is required for the proper expression of mismatch repair component MutL/MLH-1 and sensitivity against ICLs. Interestingly, formation of ICLs lead to ubiquitination-dependent subcellular relocalization of AMX-1. Taken together, our data suggest that AMX-1 functions in ICL repair in the germline.

Histone lysine demethylases and their functions in cancer

Histone lysine demethylases (KDMs) are enzymes that remove the methylation marks on lysines in nucleosomes' histone tails. These changes in methylation marks regulate gene transcription during both development and malignant transformation. Depending on which lysine residue is targeted, the effect of a given KDM on gene transcription can be either activating or repressing, and KDMs can regulate the expression of both oncogenes and tumour suppressors. Thus, the functions of KDMs can be regarded as both oncogenic and tumour suppressive, contingent on cell context and the enzyme isoform. Finally, KDMs also demethylate nonhistone proteins and have a variety of demethylase-independent functions. These epigenetic and other mechanisms that KDMs control make them important regulators of malignant tumours. Here, we present an overview of eight KDM subfamilies, their most-studied lysine targets and selected recent data on their roles in cancer stem cells, tumour aggressiveness and drug tolerance.

KDM2B Overexpression Facilitates Lytic De Novo KSHV Infection by Inducing AP-1 Activity Through Interaction with the SCF E3 Ubiquitin Ligase Complex

It is still largely unknown what host factors are involved in controlling the expression of the lytic viral gene RTA during primary infection, which determines if Kaposi's sarcoma-associated herpesvirus (KSHV) establishes latent or lytic infection. We have recently identified the histone demethylase KDM2B as a repressor of RTA expression during both de novo KSHV infection and latency based on an epigenetic factor siRNA screen. Here, we report that surprisingly, KDM2B overexpression can promote lytic de novo infection by using a mechanism that differs from what is needed for its repressor function. Our study revealed that while the DNA-binding and demethylase activities of KDM2B linked to its transcription repressive function are dispensable, its C-terminal F-box and LRR domains are required for the lytic infection-inducing function of KDM2B. We found that overexpressed KDM2B increases the half-life of the AP-1 subunit c-Jun protein and induces the AP-1 signaling pathway. This effect is dependent upon the binding of KDM2B to the SKP1-CUL1-F-box (SCF) E3 ubiquitin ligase complex via its F-box domain. Importantly, the inhibition of AP-1 reduces KDM2B-mediated lytic de novo KSHV infection. Overall, our findings indicate that KDM2B may induce the degradation of some host factors by using the SCF complex resulting in the enrichment of c-Jun. This leads to increased AP-1 transcriptional activity, which facilitates lytic gene expression following de novo infection interfering with the establishment of viral latency.SignificanceThe expression of epigenetic factors is often dysregulated in cancers or upon specific stress signals, which often results in a display of non-canonical functions of the epigenetic factors that are independent from their chromatin-modifying roles. We have previously demonstrated that KDM2B normally inhibits KSHV lytic cycle using its histone demethylase activity. Surprisingly, we found that KDM2B overexpression can promote lytic de novo infection, which does not require its histone demethylase or DNA-binding functions. Instead, KDM2B uses the SKP1-CUL1-F-box (SCF) E3 ubiquitin ligase complex to induce AP-1 transcriptional activity, which promotes lytic gene expression. This is the first report that demonstrates a functional link between SFC^KDM2B and AP-1 in the regulation of KSHV lytic cycle.

Clinical Manifestations and Epigenetic Regulation of Oral Herpesvirus Infections

The oral cavity is often the first site where viruses interact with the human body. The oral epithelium is a major site of viral entry, replication and spread to other cell types, where chronic infection can be established. In addition, saliva has been shown as a primary route of person-to-person transmission for many viruses. From a clinical perspective, viral infection can lead to several oral manifestations, ranging from common intraoral lesions to tumors. Despite the clinical and biological relevance of initial oral infection, little is known about the mechanism of regulation of the viral life cycle in the oral cavity. Several viruses utilize host epigenetic machinery to promote their own life cycle. Importantly, viral hijacking of host chromatin-modifying enzymes can also lead to the dysregulation of host factors and in the case of oncogenic viruses may ultimately play a role in promoting tumorigenesis. Given the known roles of epigenetic regulation of viral infection, epigenetic-targeted antiviral therapy has been recently explored as a therapeutic option for chronic viral infection. In this review, we highlight three herpesviruses with known roles in oral infection, including herpes simplex virus type 1, Epstein–Barr virus and Kaposi’s sarcoma-associated herpesvirus. We focus on the respective oral clinical manifestations of these viruses and their epigenetic regulation, with a specific emphasis on the viral life cycle in the oral epithelium.

Nutrient regulation of the flow of genetic information by O-GlcNAcylation

O-linked-β-N-acetylglucosamine (O-GlcNAc) is a post-translational modification (PTM) that is actively added to and removed from thousands of intracellular proteins. As a PTM, O-GlcNAcylation tunes the functions of a protein in various ways, such as enzymatic activity, transcriptional activity, subcellular localization, intermolecular interactions, and degradation. Its regulatory roles often interplay with the phosphorylation of the same protein. Governed by 'the Central Dogma', the flow of genetic information is central to all cellular activities. Many proteins regulating this flow are O-GlcNAc modified, and their functions are tuned by the cycling sugar. Herein, we review the regulatory roles of O-GlcNAcylation on the epigenome, in DNA replication and repair, in transcription and in RNA processing, in protein translation and in protein turnover.

GASC1 promotes hepatocellular carcinoma progression by inhibiting the degradation of ROCK2

Hepatocellular carcinoma (HCC) is a devastating malignancy without targeted therapeutic options. Our results indicated that the histone demethylase GASC1 signature is associated with later tumor stage and poorer survival in HCC patients. GASC1 depletion led to diminished HCC proliferation and tumor growth. A distinct heterogeneity in GASC1 levels was observed among HCC cell populations, predicting their inherent high or low tumor-initiating capacity. Mechanistically, GASC1 is involved in the regulation of several components of the Rho-GTPase signaling pathway including its downstream target ROCK2. GASC1 demethylase activity ensured the transcriptional repression of FBXO42, a ROCK2 protein-ubiquitin ligase, thereby inhibiting ROCK2 degradation via K63-linked poly-ubiquitination. Treatment with the GASC1 inhibitor SD70 impaired the growth of both HCC cell lines and xenografts in mice, sensitizing them to standard-of-care chemotherapy. This work identifies GASC1 as a malignant-cell-selective target in HCC, and GASC1-specific therapeutics represent promising candidates for new treatment options to control this malignancy.

Roles and mechanisms of BAP1 deubiquitinase in tumor suppression

The BAP1 gene has emerged as a major tumor suppressor mutated with various frequencies in numerous human malignancies, including uveal melanoma, malignant pleural mesothelioma, clear cell renal cell carcinoma, intrahepatic cholangiocarcinoma, hepatocellular carcinoma, and thymic epithelial tumors. BAP1 mutations are also observed at low frequency in other malignancies including breast, colorectal, pancreatic, and bladder cancers. BAP1 germline mutations are associated with high incidence of mesothelioma, uveal melanoma, and other cancers, defining the "BAP1 cancer syndrome." Interestingly, germline BAP1 mutations constitute an important paradigm for gene-environment interactions, as loss of BAP1 predisposes to carcinogen-induced tumorigenesis. Inactivating mutations of BAP1 are also identified in sporadic cancers, denoting the importance of this gene for normal tissue homeostasis and tumor suppression, although some oncogenic properties have also been attributed to BAP1. BAP1 belongs to the deubiquitinase superfamily of enzymes, which are responsible for the maturation and turnover of ubiquitin as well as the reversal of substrate ubiquitination, thus regulating ubiquitin signaling. BAP1 is predominantly nuclear and interacts with several chromatin-associated factors, assembling multi-protein complexes with mutually exclusive partners. BAP1 exerts its function through highly regulated deubiquitination of its substrates. As such, BAP1 orchestrates chromatin-associated processes including gene expression, DNA replication, and DNA repair. BAP1 also exerts cytoplasmic functions, notably in regulating Ca²⁺ signaling at the endoplasmic reticulum. This DUB is also subjected to multiple post-translational modifications, notably phosphorylation and ubiquitination, indicating that several signaling pathways tightly regulate its function. Recent progress indicated that BAP1 plays essential roles in multiple cellular processes including cell proliferation and differentiation, cell metabolism, as well as cell survival and death. In this review, we summarize the biological and molecular functions of BAP1 and explain how the inactivation of this DUB might cause human cancers. We also highlight some of the unresolved questions and suggest potential new directions.

Collagen Peptide Provides Saccharomyces cerevisiae with Robust Stress Tolerance for Enhanced Bioethanol Production

Efficient production of bioethanol is desirable for bioenergy large-scale applications, but it is severely challenged by ethanol and sugar stresses. Here, collagen peptide (CP), as a renewable nitrogen-containing biomass, remarkably enhanced the stress resistance of Saccharomyces cerevisiae SLL-510 against ethanol challenge, based on its unique amino acid composition. Transcriptome analysis showed that the energy, lipid, cofactor, and vitamin metabolism may involve in stress tolerance provided by CP. When CP was added into the media containing 249.99 mg/mL glucose, the bioethanol yield increased from 8.03 to 12.25% (v/v) and 11.35 to 12.29% (v/v) at 43 and 120 h, respectively. Moreover, at 286.79 mg/mL glucose, the highest yield reached 14.48% (v/v), with 99.58% glucose utilization rate. The protection and promotion effects of CP were also shown by four other industrial S. cerevisiae strains. These results coupled with the advantages of abundant reserves, cleanliness, and renewability revealed that CP is a promising economically viable and industrially scalable enhancer for bioethanol fermentation.

Mutual regulation between OGT and XIAP to control colon cancer cell growth and invasion

O-GlcNAc transferase (OGT) is an enzyme that catalyzes the O-GlcNAc modification of nucleocytoplasmic proteins and is highly expressed in many types of cancer. However, the mechanism regulating its expression in cancer cells is not well understood. This study shows that OGT is a substrate of the E3 ubiquitin ligase X-linked inhibitor of apoptosis (XIAP) which plays an important role in cancer pathogenesis. Although LSD2 histone demethylase has already been reported as an E3 ubiquitin ligase in lung cancer cells, we identified XIAP as the main E3 ubiquitin ligase in colon cancer cells. Interestingly, OGT catalyzes the O-GlcNAc modification of XIAP at serine 406 and this modification is required for the E3 ubiquitin ligase activity of XIAP toward specifically OGT. Moreover, O-GlcNAcylation of XIAP suppresses colon cancer cell growth and invasion by promoting the proteasomal degradation of OGT. Therefore, our findings regarding the reciprocal regulation of OGT and XIAP provide a novel molecular mechanism for controlling cancer growth and invasion regulated by OGT and O-GlcNAc modification.

Prenatal Hyperglycemia Exposure and Cellular Stress, a Sugar-Coated View of Early Programming of Metabolic Diseases

Worldwide, the number of people with diabetes has quadrupled since 1980 reaching 422 million in 2014 (World Health Organization). This distressing rise in diabetes also affects pregnant women and thus, in regard to early programming of adult diseases, creates a vicious cycle of metabolic dysfunction passed from one generation to another. Metabolic diseases are complex and caused by the interplay between genetic and environmental factors. High-glucose exposure during in utero development, as observed with gestational diabetes mellitus (GDM), is an established risk factor for metabolic diseases. Despite intense efforts to better understand this phenomenon of early memory little is known about the molecular mechanisms associating early exposure to long-term diseases risk. However, evidence promotes glucose associated oxidative stress as one of the molecular mechanisms able to influence susceptibility to metabolic diseases. Thus, we decided here to further explore the relationship between early glucose exposure and cellular stress in the context of early development, and focus on the concept of glycemic memory, its consequences, and sexual dimorphic and epigenetic aspects.

Emerging of lysine demethylases (KDMs): From pathophysiological insights to novel therapeutic opportunities

In recent years, there have been remarkable scientific advancements in the understanding of lysine demethylases (KDMs) because of their demethylation of diverse substrates, including nucleic acids and proteins. Novel structural architectures, physiological roles in the gene expression regulation, and ability to modify protein functions made KDMs the topic of interest in biomedical research. These structural diversities allow them to exert their function either alone or in complex with numerous other bio-macromolecules. Impressive number of studies have demonstrated that KDMs are localized dynamically across the cellular and tissue microenvironment. Their dysregulation is often associated with human diseases, such as cancer, immune disorders, neurological disorders, and developmental abnormalities. Advancements in the knowledge of the underlying biochemistry and disease associations have led to the development of a series of modulators and technical compounds. Given the distinct biophysical and biochemical properties of KDMs, in this review we have focused on advances related to the structure, function, disease association, and therapeutic targeting of KDMs highlighting improvements in both the specificity and efficacy of KDM modulation.

Epi-drugs as triple-negative breast cancer treatment

Triple-negative breast cancer (TNBC) types with poor prognosis are due to the absence of estrogen receptors, progesterone receptors and HEGFR-2. The lack of suitable therapy for TNBC has led the research community to turn toward epigenetic regulation and its protagonists that can modulate certain oncogenes and tumor suppressors. This has opened an important new field of therapy using epi-drugs, in preclinical and clinical trials. The epi-drugs are natural or synthetic molecules capable of inhibiting or modulating the activity of epigenetic proteins such as DNA methyltransferases, modulating the expression of interferon microRNAs, as well as histone methyltransferases, demethylases, acetyltransferases and deacetylases. This review investigated the epi-drugs used in the treatment of TNBC.

The Catalytic-Dependent and -Independent Roles of Lsd1 and Lsd2 Lysine Demethylases in Heterochromatin Formation in Schizosaccharomyces pombe

In eukaryotes, heterochromatin plays a critical role in organismal development and cell fate acquisition, through regulating gene expression. The evolutionarily conserved lysine-specific demethylases, Lsd1 and Lsd2, remove mono- and dimethylation on histone H3, serving complex roles in gene expression. In the fission yeast Schizosaccharomyces pombe, null mutations of Lsd1 and Lsd2 result in either severe growth defects or inviability, while catalytic inactivation causes minimal defects, indicating that Lsd1 and Lsd2 have essential functions beyond their known demethylase activity. Here, we show that catalytic mutants of Lsd1 or Lsd2 partially assemble functional heterochromatin at centromeres in RNAi-deficient cells, while the C-terminal truncated alleles of Lsd1 or Lsd2 exacerbate heterochromatin formation at all major heterochromatic regions, suggesting that Lsd1 and Lsd2 repress heterochromatic transcripts through mechanisms both dependent on and independent of their catalytic activities. Lsd1 and Lsd2 are also involved in the establishment and maintenance of heterochromatin. At constitutive heterochromatic regions, Lsd1 and Lsd2 regulate one another and cooperate with other histone modifiers, including the class II HDAC Clr3 and the Sirtuin family protein Sir2 for gene silencing, but not with the class I HDAC Clr6. Our findings explore the roles of lysine-specific demethylases in epigenetic gene silencing at heterochromatic regions.

Crystal structures of REF6 and its complex with DNA reveal diverse recognition mechanisms

Relative of Early Flowing 6 (REF6) is a DNA-sequence-specific H3K27me3/2 demethylase that contains four zinc finger (ZnF) domains and targets several thousand genes in Arabidopsis thaliana. The ZnF domains are essential for binding target genes, but the structural basis remains unclear. Here, we determined crystal structures of the ZnF domains and REF6-DNA complex, revealing a unique REF6-family-specific half-cross-braced ZnF (RCZ) domain and two C2H2-type ZnFs. DNA-binding induces a profound conformational change in the hinge region of REF6. Each REF6 recognizes six bases and DNA methylation reduces the binding affinity. Both the acidic region and basic region are important for the self-association of REF6. The REF6 DNA-binding affinity is determined by the sequence-dependent conformations of DNA and also the cooperativity in different target motifs. The conformational plasticity enables REF6 to function as a global transcriptional regulator that directly binds to many diverse genes, revealing the structural basis for the epigenetic modification recognition.

LSD1/KDM1A inhibitors in clinical trials: advances and prospects

Histone demethylase LSD1 plays key roles during carcinogenesis, targeting LSD1 is becoming an emerging option for the treatment of cancers. Numerous LSD1 inhibitors have been reported to date, some of them such as TCP, ORY-1001, GSK-2879552, IMG-7289, INCB059872, CC-90011, and ORY-2001 currently undergo clinical assessment for cancer therapy, particularly for small lung cancer cells (SCLC) and acute myeloid leukemia (AML). This review is to provide a comprehensive overview of LSD1 inhibitors in clinical trials including molecular mechanistic studies, clinical efficacy, adverse drug reactions, and PD/PK studies and offer prospects in this field.

Molecular mechanisms regulating O-linked N-acetylglucosamine (O-GlcNAc)-processing enzymes

The post-translational modification of proteins by O-linked N-acetylglucosamine (O-GlcNAc) dynamically programmes cellular physiology to maintain homoeostasis and tailor biochemical pathways to meet context-dependent cellular needs. Despite diverse roles of played by O-GlcNAc, only two enzymes act antagonistically to govern its cycling; O-GlcNAc transferase installs the monosaccharide on target proteins, and O-GlcNAc hydrolase removes it. The recent literature has exposed a network of mechanisms regulating these two enzymes to choreograph global, and target-specific, O-GlcNAc cycling in response to cellular stress and nutrient availability. Herein, we amalgamate these emerging mechanisms from a structural and molecular perspective to explore how the cell exerts fine control to regulate O-GlcNAcylation of diverse proteins in a selective fashion.

Reduction in H3K4me patterns due to aberrant expression of methyltransferases and demethylases in renal cell carcinoma: prognostic and therapeutic implications

Renal cell carcinoma (RCC) is the leading cause among cancer-related deaths due to urological cancers, which results in response to combination of genetic and epigenetic factors. Histone methylations have been implicated in renal tumorigenesis but their clinical significance and underlying pathology are unexplored. Here, we elucidated the histone 3 lysine 4 (H3K4) methylation patterns in clear cell RCC and its underlying pathology. Lower cellular levels of H3K4 mono-methylation, -dimethylation and -tri-methylation were fraternized with higher TNM staging and Fuhrman grading as well as tumor metastasis. Further, the expression profile of 20 H3K4 modifiers revealed the significant over-expression of histone demethylases compared to methyltransferases, indicating their role in the reduction of H3K4 methylation levels. In view of above facts, the role of LSD2 and KDM5A demethylases in RCC pathogenesis were explored using respective siRNAs. The RCC cells exhibited reduced cell viability after knockdown of LSD2 and KDM5A genes with concomitant induction of apoptosis. In addition, propidium iodide staining demonstrated an arrest of RCC cells at S-phase and sub-G1 phase of the cell cycle. Taken together, these observations provide new pathological insights behind the alterations of H3K4 methylation patterns in ccRCC with their prognostic and therapeutic implications.

Lysine-specific demethylase-2 is distinctively involved in brown and beige adipogenic differentiation

Transcriptional and epigenetic regulation is fundamentally involved in initiating and maintaining progression of cellular differentiation. The 2 types of thermogenic adipocytes, brown and beige, are thought to be of different origins but share functionally similar phenotypes. Here, we report that lysine-specific demethylase 2 (LSD2) regulates the expression of genes associated with lineage identity during the differentiation of brown and beige adipogenic progenitors in mice. In HB2 mouse brown preadipocytes, short hairpin RNA-mediated knockdown (KD) of LSD2 impaired formation of lipid droplet-containing adipocytes and down-regulated brown adipogenesis-associated genes. Transcriptomic analysis revealed that myogenesis-associated genes were up-regulated in LSD2-KD cells under adipogenic induction. In addition, loss of LSD2 during later phases of differentiation had no obvious influence on adipogenic traits, suggesting that LSD2 functions during earlier phases of brown adipocyte differentiation. Using adipogenic cells from the brown adipose tissues of LSD2-knockout (KO) mice, we found reduced expression of brown adipogenesis genes, whereas myogenesis genes were not affected. In contrast, when LSD2-KO cells from inguinal white adipose tissues were subjected to beige induction, these cells showed a dramatic rise in myogenic gene expression. Collectively, these results suggest that LSD2 regulates distinct sets of genes during brown and beige adipocyte formation.-Takase, R., Hino, S., Nagaoka, K., Anan, K., Kohrogi, K., Araki, H., Hino, Y., Sakamoto, A., Nicholson, T. B., Chen, T., Nakao, M. Lysine-specific demethylase-2 is distinctively involved in brown and beige adipogenic differentiation.

Regulation of histone arginine methylation/demethylation by methylase and demethylase (Review)

Histone arginine methylation is a universal post-translational modification that has been implicated in multiple cellular and sub-cellular processes, including pre-mRNA splicing, DNA damage signaling, mRNA translation, cell signaling and cell death. Despite these important roles, the understanding of its regulation with respect to certain other modifications, such as phosphorylation and acetylation, is very poor. Thus far, few histone arginine demethylases have been identified in mammalian cells, compared with nine protein arginine methyltransferases (PRMTs) that have been reported. Studies have reported that aberrant histone arginine methylation is strongly associated with carcinogenesis and metastasis. This increases the requirement for understanding the regulation of histone arginine demethylation. The present review summarizes the published studies and provides further insights into histone arginine methylases and demethylases.

O-GlcNAc Transferase Suppresses Inflammation and Necroptosis by Targeting Receptor-Interacting Serine/Threonine-Protein Kinase 3

Elevated glucose metabolism in immune cells represents a hallmark feature of many inflammatory diseases, such as sepsis. However, the role of individual glucose metabolic pathways during immune cell activation and inflammation remains incompletely understood. Here, we demonstrate a previously unrecognized anti-inflammatory function of the O-linked β-N-acetylglucosamine (O-GlcNAc) signaling associated with the hexosamine biosynthesis pathway (HBP). Despite elevated activities of glycolysis and the pentose phosphate pathway, activation of macrophages with lipopolysaccharide (LPS) resulted in attenuated HBP activity and protein O-GlcNAcylation. Deletion of O-GlcNAc transferase (OGT), a key enzyme for protein O-GlcNAcylation, led to enhanced innate immune activation and exacerbated septic inflammation. Mechanistically, OGT-mediated O-GlcNAcylation of the serine-threonine kinase RIPK3 on threonine 467 (T467) prevented RIPK3-RIPK1 hetero- and RIPK3-RIPK3 homo-interaction and inhibited downstream innate immunity and necroptosis signaling. Thus, our study identifies an immuno-metabolic crosstalk essential for fine-tuning innate immune cell activation and highlights the importance of glucose metabolism in septic inflammation.

The Many Ways by Which O-GlcNAcylation May Orchestrate the Diversity of Complex Glycosylations

Unlike complex glycosylations, O-GlcNAcylation consists of the addition of a single N-acetylglucosamine unit to serine and threonine residues of target proteins, and is confined within the nucleocytoplasmic and mitochondrial compartments. Nevertheless, a number of clues tend to show that O-GlcNAcylation is a pivotal regulatory element of its complex counterparts. In this perspective, we gather the evidence reported to date regarding this connection. We propose different levels of regulation that encompass the competition for the nucleotide sugar UDP-GlcNAc, and that control the wide class of glycosylation enzymes via their expression, catalytic activity, and trafficking. We sought to better envision that nutrient fluxes control the elaboration of glycans, not only at the level of their structure composition, but also through sweet regulating actors.

Lysine‑specific demethylase 2 contributes to the proliferation of small cell lung cancer by regulating the expression of TFPI‑2

The present study aimed to investigate the effect of lysine‑specific demethylase 2 (LSD2) in small cell lung cancer (SCLC) and explore its underlying regulatory mechanism. Cell growth was tested by MTT assay and mRNA and protein expression was determined by quantitative polymerase chain reaction (q‑PCR) and western blot analysis, respectively. Chromatin immunoprecipitation (ChIP) was used to investigate the degree of H3K4me2 enrichment in the promoter region of tissue factor pathway inhibitor‑2 (TFPI‑2). SCLC tissues and cell lines presented significantly higher expression of LSD2 and DNA methyltransferase 3B (DNMT3B) and lower expression of TFPI‑2 compared with the controls. In H1417 cells LSD2 overexpression increased the mRNA and protein expression of DNMT3B, while inhibiting the mRNA and protein expression of TFPI‑2. Following transfection with short interfering (si) RNA‑DNMT3B, the expression of TFPI‑2 increased in H1417 cells. The results of ChIP demonstrated that compared with the controls, H3K4me1 enrichment in the TFPI‑2 promoter region was to a lower degree in the H1417 cells with LSD2 overexpression and a higher degree in the H1417 cells with LSD2 silencing. MTT assays revealed that LSD2 overexpression significantly promoted the growth of H69, DMS‑114 and H1417 cells, which was contradictory to the effect on LSD2 silencing. Compared with the LSD2 overexpression cells, SCLC cells with simultaneous overexpression of LSD2 and TFPI‑2 demonstrated a decreased proliferation. These results suggest that LSD2 achieves a promoting effect on SCLC by indirectly regulating TFPI‑2 expression through the mediation of DNMT3B expression or through the regulation of the demethylation of H3K4me1 in the promoter region of the TFPI‑2 gene.

O-GlcNAc in cancer: An Oncometabolism-fueled vicious cycle

Cancer cells exhibit unregulated growth, altered metabolism, enhanced metastatic potential and altered cell surface glycans. Fueled by oncometabolism and elevated uptake of glucose and glutamine, the hexosamine biosynthetic pathway (HBP) sustains glycosylation in the endomembrane system. In addition, the elevated pools of UDP-GlcNAc drives the O-GlcNAc modification of key targets in the cytoplasm, nucleus and mitochondrion. These targets include transcription factors, kinases, key cytoplasmic enzymes of intermediary metabolism, and electron transport chain complexes. O-GlcNAcylation can thereby alter epigenetics, transcription, signaling, proteostasis, and bioenergetics, key 'hallmarks of cancer'. In this review, we summarize accumulating evidence that many cancer hallmarks are linked to dysregulation of O-GlcNAc cycling on cancer-relevant targets. We argue that onconutrient and oncometabolite-fueled elevation increases HBP flux and triggers O-GlcNAcylation of key regulatory enzymes in glycolysis, Kreb's cycle, pentose-phosphate pathway, and the HBP itself. The resulting rerouting of glucose metabolites leads to elevated O-GlcNAcylation of oncogenes and tumor suppressors further escalating elevation in HBP flux creating a 'vicious cycle'. Downstream, elevated O-GlcNAcylation alters DNA repair and cellular stress pathways which influence oncogenesis. The elevated steady-state levels of O-GlcNAcylated targets found in many cancers may also provide these cells with a selective advantage for sustained growth, enhanced metastatic potential, and immune evasion in the tumor microenvironment.

Checkpoint kinase 1-induced phosphorylation of O-linked β-N-acetylglucosamine transferase regulates the intermediate filament network during cytokinesis

Checkpoint kinase 1 (Chk1) is a kinase instrumental for orchestrating DNA replication, DNA damage checkpoints, the spindle assembly checkpoint, and cytokinesis. Despite Chk1's pivotal role in multiple cellular processes, many of its substrates remain elusive. Here, we identified O-linked β-N-acetylglucosamine (O-GlcNAc)-transferase (OGT) as one of Chk1's substrates. We found that Chk1 interacts with and phosphorylates OGT at Ser-20, which not only stabilizes OGT, but also is required for cytokinesis. Phospho-specific antibodies of OGT-pSer-20 exhibited specific signals at the midbody of the cell, consistent with midbody localization of OGT as reported previously. Moreover, phospho-deficient OGT (S20A) cells attenuated cellular O-GlcNAcylation levels and also reduced phosphorylation of Ser-71 in the cytoskeletal protein vimentin, a modification critical for severing vimentin filament during cytokinesis. Consequently, elongated vimentin bridges were observed in cells depleted of OGT via an siOGT-based approach. Lastly, expression of plasmids resistant to siOGT efficiently rescued the vimentin bridge phenotype, but the OGT-S20A rescue plasmids did not. Our results suggest a Chk1-OGT-vimentin pathway that regulates the intermediate filament network during cytokinesis.