RB1 methylation by SMYD2 enhances cell cycle progression through an increase of RB1 phosphorylation

Role of SMYD2 in gastrointestinal cancer progression (Review)

Gastrointestinal cancer is one of the most prevalent malignancies in humans and is often associated with a poor prognosis. Understanding the molecular mechanisms underlying cancer progression and severity is essential for the development of effective cancer therapies. Abnormal protein methylation is associated with the occurrence and advancement of cancer, highlighting the importance of protein methyltransferase research. SET and MYND domain-containing protein 2 (SMYD2), a lysine methyltransferase, has emerged as a promising small molecule target for cancer treatment. Notably, SMYD2 is implicated in the pathogenesis of several diseases, including gastrointestinal cancer. SMYD2 is closely associated with the tumorigenesis, proliferation, migration and other biological processes of gastrointestinal cancer, indicating its potential as a novel therapeutic target. The present review offers an in-depth analysis of SMYD2, covering its structural characteristics, regulatory pathways and functional significance. By assessing the biological roles and therapeutic potential of SMYD2, the current review presents fresh insights and perspectives for advancing research in different types of gastrointestinal cancer.

Mechanism of SMYD2 promoting stemness maintenance of bladder cancer stem cells by regulating PYCR1 expression and PINK1/Parkin mitophagy pathway

SET and MYND domain‑containing protein 2 (SMYD2), an identified protein‑lysine methyltransferase, is key for bladder cancer (BC) progression. The tumor‑formation capacity and metastatic potential of bladder cancer stem cells (BCSCs) are due to their stemness characteristics. The present study explores the mechanism of SMYD2 in promoting BCSC stemness maintenance by pyrroline‑5‑carboxylate reductase 1 (PYCR1). BC cells were treated with PYCR1, SMYD2 and putative kinase 1 (PINK1) small interfering (si)RNA, pcDNA3.1‑PYCR1 and pcDNA3.1‑SMYD2. Mito‑Tracker Green and light chain‑3B (LC3B) expression, in vitro colony formation ability and tumor stemness were assessed, as well as histone H3 lysine 4 trimethylation (H3K4me3) enrichment and PYCR1, SMYD2, H3K4me3, LC3B II/I, p62, PINK1, Parkin, Nanog and SRY‑box transcription factor 2 (Sox2) expression. A nude mouse xenograft model was used for in vivo verification. PYCR1 mRNA and protein expression were elevated in BCSCs. Following PYCR1 or SMYD2 siRNA treatment, PYCR1, SMYD2 and CD44+CD33+ expression, cancer cell colony formation, number of tumor spheres and Nanog and Sox2 expression were decreased, but pcDNA3.1‑PYCR1 or pcDNA3.1‑SMYD2 transfection enhanced BCSC stemness maintenance. SMYD2 was associated with PYCR1 expression. SMYD2 upregulated PYCR1 expression through H3K4me3, subsequently activating the PINK1/Parkin mitophagy pathway, which supports maintenance of BCSC stemness.

SMAD2/3-SMYD2 and developmental transcription factors cooperate with cell-cycle inhibitors to guide tissue formation

Tissue formation and organ homeostasis are achieved by precise coordination of proliferation and differentiation of stem cells and progenitors. While deregulation of these processes can result in degenerative disease or cancer, their molecular interplays remain unclear. Here we show that the switch of human pluripotent stem cell (hPSC) self-renewal to differentiation is associated with the induction of distinct cyclin-dependent kinase inhibitors (CDKIs). In hPSCs, Activin/Nodal/TGFβ signaling maintains CDKIs in a poised state via SMAD2/3-NANOG-OCT4-EZH2-SNON transcriptional complex. Upon gradual differentiation, CDKIs are induced by successive transcriptional complexes between SMAD2/3-SMYD2 and developmental regulators such as EOMES, thereby lengthening the G1 phase. This, in turn, induces SMAD2/3 transcriptional activity by blocking its linker phosphorylation. Such SMAD2/3-CDKI positive feedback loops drive the exit from pluripotency and stepwise cell-fate specification that could be harnessed for producing cells for therapeutic applications. Our study uncovers fundamental mechanisms of how cell-fate specification is interconnected to cell-cycle dynamics and provides insight into autonomous circuitries governing tissue self-formation.

The SET29 and SET7 proteins of Leishmania donovani exercise non-redundant convergent as well as collaborative functions in moderating the parasite's response to oxidative stress

SET proteins are lysine methyltransferases. In investigating Leishmania donovani SET29, we found depletion of LdSET29 by two-thirds did not affect promastigote growth, nor alter the parasite's response to UV-induced or HU-induced stress, but made it more tolerant to H2O2-induced oxidizing environment. The deviant response to oxidative stress was coupled to lowered accumulation of reactive oxygen species, which was linked to enhanced scavenging activity. The set29 mutants' response to H2O2 exposure was similar to that of set7 mutants, prompting an investigation into genetic and physical interactions between the two proteins. While neither protein could rescue the aberrant phenotypes of the other set mutant, the two proteins interacted physically in vitro and in vivo. Transcriptome analyses revealed that neither protein regulated global gene expression, but LdSET7 controlled transcript levels of a limited number of genes, including several peroxidases. In working towards identifying targets through which SET7/SET29 mediate the cell's response to an oxidative milieu, we found HSP60/CNP60 and TCP1 to be possible candidates. LdHSP60 has earlier been implicated in the regulation of the response of virulent promastigotes to H2O2 exposure, and LdTCP1 has previously been found to have a protective effect against oxidative stress. set7 and set29 mutants survived more proficiently in host macrophages as well. The data suggest an alliance between LdSET29 and LdSET7 in mounting the parasite's response to oxidative stress, each protein playing its own distinctive role. They ensure the parasite not only establishes infection but also maintains the balance with host cells to enable the persistence of infection.

NSD3 protein methylation and stabilization transforms human ES cells into variant state

Cultured human embryonic stem cells (hESCs) can develop genetic anomalies that increase their susceptibility to transformation. In this study, we characterized a variant hESC (vhESC) line and investigated the molecular mechanisms leading to the drift towards a transformed state. Our findings revealed that vhESCs up-regulate EMT-specific markers, accelerate wound healing, exhibit compromised lineage differentiation, and retain pluripotency gene expression in teratomas. Furthermore, we discovered an altered epigenomic landscape and overexpression of the lysine methyltransferases EHMT1, EHMT2, and NSD group of proteins in vhESCs. Remarkably, depleting NSD3 oncogene reversed the molecular and phenotypic changes in vhESCs. We identified a detailed mechanism where EHMT2 interacts and methylates NSD3 at lysine 477, stabilizing its protein levels in vhESCs. In addition, we showed that NSD3 levels are regulated by protein degradation in hESCs, and its stabilization leads to the emergence of the variant state. Overall, our study identify that misregulation of NSD3 in pluripotent stem cells, through methylation-mediated abrogation of its protein degradation, drives hESCs towards oncogenic transformation.

Emergent properties of the lysine methylome reveal regulatory roles via protein interactions and histone mimicry

AIMS

Epigenomics has significantly advanced through the incorporation of Systems Biology approaches. This study aims to investigate the human lysine methylome as a system, using a data-science approach to reveal its emergent properties, particularly focusing on histone mimicry and the broader implications of lysine methylation across the proteome.

METHODS

We employed a data-science-driven OMICS approach, leveraging high-dimensional proteomic data to study the lysine methylome. The analysis focused on identifying sequence-based recognition motifs of lysine methyltransferases and evaluating the prevalence and distribution of lysine methylation across the human proteome.

RESULTS

Our analysis revealed that lysine methylation impacts 15% of the known proteome, with a notable bias toward mono-methylation. We identified sequence-based recognition motifs of 13 lysine methyltransferases, highlighting candidates for histone mimicry. These findings suggest that the selective inhibition of individual lysine methyltransferases could have systemic effects rather than merely targeting histone methylation.

CONCLUSIONS

The lysine methylome has significant mechanistic value and should be considered in the design and testing of therapeutic strategies, particularly in precision oncology. The study underscores the importance of considering non-histone proteins involved in DNA damage and repair, cell signaling, metabolism, and cell cycle pathways when targeting lysine methyltransferases.

P16INK4A drives RB1 degradation by UTP14A-catalyzed K810 ubiquitination

P16INK4A expression is inversely associated with RB1 expression in cancer cells, and P16INK4A inhibits CDK4-catalyzed RB1 phosphorylation. How P16INK4A and RB1 coordinately express and regulate the cell cycle remains to be studied. In the present study, we found that P16INK4A upregulated the E3 ligase UTP14A, which led to the ubiquitination of RB1 at K810 and RB1 degradation. P16INK4A loss consistently disrupted the UTP14A-mediated degradation of RB1 and caused RB1 accumulation. Functionally, P16INK4A loss inhibited RB1 ubiquitination in a cell cycle progression-independent fashion and inhibited proteome-scale ubiquitination in a cell cycle progression-dependent manner. Our findings indicate that there is a negative feedback loop between P16INK4A and RB1 expression and that disruption of this loop may partially rescue the biological outcomes of P16INK4A loss. We also revealed a hitherto unknown function for P16 INK4A in regulating proteome-scale ubiquitination by inhibiting cell proliferation, which may be useful for the development of anticancer drugs.

Targeting histone methylation and demethylation for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide, facing increasing challenges in terms of prevention and treatment. The methylation of lysine and arginine residues on histone proteins is dynamically controlled by histone methyltransferases (HMTs) and histone demethylases (HDMs), regulating chromatin structure and gene transcription. Mutations, genetic translocations, and altered gene expression involving HMTs and HDMs are frequently observed in NAFLD. HMTs and HDMs are receiving increasing attention in regulating NALFD. Targeting specific HMTs and HDMs for drug development is becoming a new strategy for treating NAFLD. This review provides a comprehensive summary of the regulatory mechanism of histone methylation/demethylation in NAFLD. Additionally, we discuss the potential applications of HMTs and HDMs inhibitors in preventing NAFLD, which may provide a scientific basis for the treatment of NAFLD.

CircSP3 encodes SP3-461aa to promote ccRCC progression via stabilizing MYH9 and activating the PI3K-Akt signaling pathway

Clear cell renal cell carcinoma (ccRCC) is a primary kidney cancer with high aggressive phenotype and extremely poor prognosis. Accumulating evidence suggests that circular RNAs (circRNAs) play pivotal roles in the occurrence and development of various human cancers. However, the expression, clinical significance and regulatory role of circRNAs in ccRCC remain largely unclear. Here we report that circSP3 to be increased in tissues from ccRCC patients and ccRCC cells, and to positively correlate with ccRCC malignant features. Knockdown of circSP3 inhibits proliferation, triggers apoptosis, and reduces migration and invasion in different ccRCC cells in vitro. Correspondingly, circSP3 overexpression Promote ccRCC tumorigenicity in a mouse xenograft model. Mechanistically, circSP3 could bind with the ribosome to initiate the translation process to encodes a novel 461-amino acid peptide referred to as SP3-461aa, which protects the MYH9 protein from proteasomal degradation. SP3-461aa played a pivotal role in mediating the oncogenic effects of circSP3 by interacting with the MYH9 protein and activating the PI3K-Akt signaling pathway. These findings suggested that circSP3 plays an important role in ccRCC development and could be a potential biomarker for the treatment and prognosis of ccRCC.

Epigenetic contribution to cancer

Epigenetics has transformed our understanding of cancer by revealing how changes in gene activity, which do not alter the DNA itself, can initiate and progress the disease. These changes include adjustments in DNA methylation, histone configuration, and non-coding RNA activity. For instance, DNA methylation can inactivate genes that typically protect against cancer, leading to broader genomic instability. Histone modifications can alter how tightly DNA is wound, influencing which genes are active or silenced; while non-coding RNAs can interfere with the messages that direct protein production, impacting cancer-related processes. Unlike genetic mutations, which are permanent and irreversible, epigenetic changes provide a malleable target for therapeutic intervention, allowing potentially reversible adjustments to gene expression patterns. This flexibility is essential in the complex landscape of cancer where static genetic solutions may be insufficient. Additionally, epigenetics bridges the gap between genetic predispositions and environmental influences on cancer, offering a comprehensive framework for understanding how lifestyle factors and external exposures impact cancer risk and progression. The integration of epigenetics into cancer research not only enhances our understanding of the disease but also opens innovative avenues for intervention that were previously unexplored in traditional genetic-focused studies. Technologies like advanced sequencing and precise epigenetic modification are paving the way for early cancer detection and more personalized treatment approaches, highlighting the critical role of epigenetics in modern cancer care.

Recent progress in retinoblastoma: Pathogenesis, presentation, diagnosis and management

Retinoblastoma, the primary ocular malignancy in pediatric patients, poses a substantial threat to mortality without prompt and effective management. The prognosis for survival and preservation of visual acuity hinges upon the disease severity at the time of initial diagnosis. Notably, retinoblastoma has played a crucial role in unraveling the genetic foundations of oncogenesis. The process of tumorigenesis commonly begins with the occurrence of biallelic mutation in the RB1 tumor suppressor gene, which is then followed by a cascade of genetic and epigenetic alterations that correspond to the clinical stage and pathological features of the tumor. The RB1 gene, recognized as a tumor suppressor, encodes the retinoblastoma protein, which plays a vital role in governing cellular replication through interactions with E2F transcription factors and chromatin remodeling proteins. The diagnosis and treatment of retinoblastoma necessitate consideration of numerous factors, including disease staging, germline mutation status, family psychosocial factors, and the resources available within the institution. This review has systematically compiled and categorized the latest developments in the diagnosis and treatment of retinoblastoma which enhanced the quality of care for this pediatric malignancy.

Lysine methyltransferase SMYD2 enhances androgen receptor signaling to modulate CRPC cell resistance to enzalutamide

Androgen receptors (ARs) play key roles in prostate cancer (PCa) progression and castration-resistant prostate cancer (CRPC) resistance to drug therapy. SET and MYND domain containing protein 2 (SMYD2), a lysine methyltransferase, has been reported to promote tumors by transcriptionally methylating important oncogenes or tumor repressor genes. However, the role of SMYD2 in CRPC drug resistance remains unclear. In this study, we found that SMYD2 expression was significantly upregulated in PCa tissues and cell lines. High SMYD2 expression indicated poor CRPC-free survival and overall survival in patients. SMYD2 knockdown dramatically inhibited the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) potential of 22Rv1 and C4-2 cells. Conversely, ectopic overexpression of SMYD2 promoted these effects in 22Rv1 and C4-2 cells. Mechanistically, SMYD2 methylated and phosphorylated ARs to affect AR ubiquitination and proteasome degradation, which further alters the AR transcriptome in CRPC cells. Importantly, the SMYD2 inhibitor AZ505 had a synergistic therapeutic effect with enzalutamide in CRPC cells and mouse models; however, it could also re-sensitize resistant CRPC cells to enzalutamide. Our findings demonstrated that SMYD2 enhances the methylation and phosphorylation of ARs and affects AR ubiquitination and proteasome degradation to modulate CRPC cell resistance to enzalutamide, indicating that SMYD2 serves as a crucial oncogene in PCa and is an ideal therapeutic target for CRPC.

Histone methyltransferase SUV420H1/KMT5B contributes to poor prognosis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a high rate of recurrence and poor prognosis, even after curative surgery. Multikinase inhibitors have been applied for HCC patients, but their effect has been restricted. This study aims to clarify the clinical impact of SUV420H1/KMT5B, one of the methyltransferases for histone H4 at lysine 20, and elucidate the novel mechanisms of HCC progression. We retrospectively investigated SUV420H1 expression using HCC clinical tissue samples employing immunohistochemical analysis (n = 350). We then performed loss-of-function analysis of SUV420H1 with cell cycle analysis, migration assay, invasion assay and RNA sequence for Gene Ontology (GO) pathway analysis in vitro, and animal experiments with xenograft mice in vivo. The SUV420H1-high-score group (n = 154) had significantly poorer prognosis for both 5-year overall and 2-year/5-year disease-free survival than the SUV420H1-low-score group (n = 196) (p < 0.001 and p < 0.05, respectively). The SUV420H1-high-score group had pathologically larger tumor size, more tumors, poorer differentiation, and more positive vascular invasion than the SUV420H1-low-score group. Multivariate analysis demonstrated that SUV420H1 high score was the poorest independent factor for overall survival. SUV420H1 knockdown could suppress cell cycle from G1 to S phase and cell invasion. GO pathway analysis showed that SUV420H1 contributed to cell proliferation, cell invasion, and/or metastasis. Overexpression of SUV420H1 clinically contributed to poor prognosis in HCC, and the inhibition of SUV420H1 could repress tumor progression and invasion both in vitro and in vivo; thus, further analyses of SUV420H1 are necessary for the discovery of future molecularly targeted drugs.

Tumor-suppressive functions of protein lysine methyltransferases

Protein lysine methyltransferases (PKMTs) play crucial roles in histone and nonhistone modifications, and their dysregulation has been linked to the development and progression of cancer. While the majority of studies have focused on the oncogenic functions of PKMTs, extensive evidence has indicated that these enzymes also play roles in tumor suppression by regulating the stability of p53 and β-catenin, promoting α-tubulin-mediated genomic stability, and regulating the transcription of oncogenes and tumor suppressors. Despite their contradictory roles in tumorigenesis, many PKMTs have been identified as potential therapeutic targets for cancer treatment. However, PKMT inhibitors may have unintended negative effects depending on the specific cancer type and target enzyme. Therefore, this review aims to comprehensively summarize the tumor-suppressive effects of PKMTs and to provide new insights into the development of anticancer drugs targeting PKMTs.

Computational approach for assessing the involvement of SMYD2 protein in human cancers using TCGA data

BACKGROUND

SMYD2 is a protein of the SET and MYND domain-containing family SMYD. It can methylate the lysine residue of various histone and nonhistone cancer-related proteins and plays a critical role in tumorigenesis. Although emerging evidence supports the association of SMYD2 in the progression of cancers, but its definitive effect is not yet clear. Therefore, further study of the gene in relation with cancer progression needs to be conducted. In the current study, investigators used TCGA data to determine the potential carcinogenic effect of SMYD2 in 11 cancer types. The transcriptional expression, survival rate, mutations, enriched pathways, and Gene Ontology of the SMYD2 were explored using different bioinformatics tools and servers. In addition, we also examined the correlation between SMYD2 gene expression and immunocyte infiltration in multiple cancer types.

RESULTS

Findings revealed that higher expression of SMYD2 was significantly correlated with cancer incidents. In CESC and KIRC, the mRNA expression of SMYD2 was significantly correlated with overall survival (OS). In BRCA, KIRC, COAD, and HNSC, the mRNA expression of SMYD2 was significantly correlated with disease-free survival (DFS). We detected 15 missense, 4 truncating, 4 fusions, and 1 splice type of mutation. The expression of SMYD2 was significantly correlated with tumor purity and immunocyte infiltration in six cancer types. The gene GNPAT was highly associated with SMYD2. Significant pathways and Gene Ontology (GO) terms for co-expressed genes were associated to various processes linked with cancer formation.

CONCLUSION

Collectively, our data-driven results may provide reasonably comprehensive insights for understanding the carcinogenic effect of SMYD2. It suggests that SMYD2 might be used as a significant target for identifying new biomarkers for various human tumors.

Histone and DNA Methylation as Epigenetic Regulators of DNA Damage Repair in Gastric Cancer and Emerging Therapeutic Opportunities

Gastric cancer (GC), one of the most common malignancies worldwide, is a heterogeneous disease developing from the accumulation of genetic and epigenetic changes. One of the most critical epigenetic alterations in GC is DNA and histone methylation, which affects multiple processes in the cell nucleus, including gene expression and DNA damage repair (DDR). Indeed, the aberrant expression of histone methyltransferases and demethylases influences chromatin accessibility to the DNA repair machinery; moreover, overexpression of DNA methyltransferases results in promoter hypermethylation, which can suppress the transcription of genes involved in DNA repair. Several DDR mechanisms have been recognized so far, with homologous recombination (HR) being the main pathway involved in the repair of double-strand breaks. An increasing number of defective HR genes are emerging in GC, resulting in the identification of important determinants of therapeutic response to DDR inhibitors. This review describes how both histone and DNA methylation affect DDR in the context of GC and discusses how alterations in DDR can help identify new molecular targets to devise more effective therapeutic strategies for GC, with a particular focus on HR-deficient tumors.

Lysine methyltransferase SMYD2 inhibits antiviral innate immunity by promoting IRF3 dephosphorylation

Phosphorylation of IRF3 is critical to induce type I interferon (IFN-I) production in antiviral innate response. Here we report that lysine methyltransferase SMYD2 inhibits the expressions of IFN-I and proinflammatory cytokines in macrophages upon viral infections. The Smyd2-deficient mice are more resistant to viral infection by producing more IFN-I and proinflammatory cytokines. Mechanistically, SMYD2 inhibits IRF3 phosphorylation in macrophages in response to viral infection independent of its methyltransferase activity. We found that SMYD2 interacts with the DNA-binding domain (DBD) and IRF association domain (IAD) domains of IRF3 by its insertion SET domain (SETi) and could recruit phosphatase PP1α to enhance its interaction with IRF3, which leads to decreased phosphorylation of IRF3 in the antiviral innate response. Our study identifies SMYD2 as a negative regulator of IFN-I production against virus infection. The new way of regulating IRF3 phosphorylation will provide insight into the understanding of IFN-I production in the innate response and possible intervention of the related immune disorders.

GART Functions as a Novel Methyltransferase in the RUVBL1/β-Catenin Signaling Pathway to Promote Tumor Stemness in Colorectal Cancer

Tumor stemness is associated with the recurrence and incurability of colorectal cancer (CRC), which lacks effective therapeutic targets and drugs. Glycinamide ribonucleotide transformylase (GART) fulfills an important role in numerous types of malignancies. The present study aims to identify the underlying mechanism through which GART may promote CRC stemness, as to developing novel therapeutic methods. An elevated level of GART is associated with poor outcomes in CRC patients and promotes the proliferation and migration of CRC cells. CD133+ cells with increased GART expression possess higher tumorigenic and proliferative capabilities both in vitro and in vivo. GART is identified to have a novel methyltransferase function, whose enzymatic activity center is located at the E948 site. GART also enhances the stability of RuvB-like AAA ATPase 1 (RUVBL1) through methylating its K7 site, which consequently aberrantly activates the Wnt/β-catenin signaling pathway to induce tumor stemness. Pemetrexed (PEM), a compound targeting GART, combined with other chemotherapy drugs greatly suppresses tumor growth both in a PDX model and in CRC patients. The present study demonstrates a novel methyltransferase function of GART and the role of the GART/RUVBL1/β-catenin signaling axis in promoting CRC stemness. PEM may be a promising therapeutic agent for the treatment of CRC.

SMYD2 regulates vascular smooth muscle cell phenotypic switching and intimal hyperplasia via interaction with myocardin

The SET and MYND domain-containing protein 2 (SMYD2) is a histone lysine methyltransferase that has been reported to regulate carcinogenesis and inflammation. However, its role in vascular smooth muscle cell (VSMC) homeostasis and vascular diseases has not been determined. Here, we investigated the role of SMYD2 in VSMC phenotypic modulation and vascular intimal hyperplasia and elucidated the underlying mechanism. We observed that SMYD2 expression was downregulated in injured carotid arteries in mice and phenotypically modulated VSMCs in vitro. Using an SMC-specific SMYD2 knockout mouse model, we found that SMYD2 ablation in VSMCs exacerbated neointima formation after vascular injury in vivo. Conversely, SMYD2 overexpression inhibited VSMC proliferation and migration in vitro and attenuated arterial narrowing in injured vessels in mice. SMYD2 downregulation promoted VSMC phenotypic switching accompanied with enhanced proliferation and migration. Mechanistically, genome-wide transcriptome analysis and loss/gain-of-function studies revealed that SMYD2 up-regulated VSMC contractile gene expression and suppressed VSMC proliferation and migration, in part, by promoting expression and transactivation of the master transcription cofactor myocardin. In addition, myocardin directly interacted with SMYD2, thereby facilitating SMYD2 recruitment to the CArG regions of SMC contractile gene promoters and leading to an open chromatin status around SMC contractile gene promoters via SMYD2-mediated H3K4 methylation. Hence, we conclude that SMYD2 is a novel regulator of VSMC contractile phenotype and intimal hyperplasia via a myocardin-dependent epigenetic regulatory mechanism.

Lysine Methyltransferase SMYD1 Regulates Myogenesis via skNAC Methylation

The SMYD family is a unique class of lysine methyltransferases (KMTases) whose catalytic SET domain is split by a MYND domain. Among these, Smyd1 was identified as a heart- and skeletal muscle-specific KMTase and is essential for cardiogenesis and skeletal muscle development. SMYD1 has been characterized as a histone methyltransferase (HMTase). Here we demonstrated that SMYD1 methylates is the Skeletal muscle-specific splice variant of the Nascent polypeptide-Associated Complex (skNAC) transcription factor. SMYD1-mediated methylation of skNAC targets K1975 within the carboxy-terminus region of skNAC. Catalysis requires physical interaction of SMYD1 and skNAC via the conserved MYND domain of SMYD1 and the PXLXP motif of skNAC. Our data indicated that skNAC methylation is required for the direct transcriptional activation of myoglobin (Mb), a heart- and skeletal muscle-specific hemoprotein that facilitates oxygen transport. Our study revealed that the skNAC, as a methylation target of SMYD1, illuminates the molecular mechanism by which SMYD1 cooperates with skNAC to regulate transcriptional activation of genes crucial for muscle functions and implicates the MYND domain of the SMYD-family KMTases as an adaptor to target substrates for methylation.

SETDB1 confers colorectal cancer metastasis by regulation of WNT/β-catenin signaling

BACKGROUND

Metastasis is a critical step in tumor development; however, its specific molecular mechanism is still not fully understood. SETDB1 overexpression is associated with tumor progression and poor prognosis. Here, we explored a novel mechanism by which SETDB1 promotes tumor metastasis in colorectal cancer.

METHODS

We conducted database and clinical specimen analysis to determine the expression level of SETDB1 in colorectal cancer, as well as the prognosis of colorectal cancer with overexpressed SETDB1. We used wound healing assays, Transwell assays, and animal studies to study the effect of SETDB1 on colorectal cancer. We performed western blotting, qRT-PCR, immunofluorescence, and co-immunoprecipitation to explore the underlying associations between SETDB1 and β-catenin. We further used wound healing assays, Transwell assays, and animal studies to verify the relationship between SETDB1 and Wnt/β-catenin.

RESULTS

SETDB1 expression was upregulated in colorectal cancer and correlated with poor prognosis. Low expression of SETDB1 decreased invasion and metastasis in colorectal cancer. Low-expression of SETDB1 in colorectal tumor cells decreased β-catenin expression and its nuclear import. We also found that SETDB1 can bind and directly methylate β-catenin, Lastly, we discovered that this metastatic ability could be decreased by activating the Wnt/β-catenin pathway with SETDB1 knock-down.

CONCLUSION

SETDB1 is highly expressed in colorectal cancer and plays an important role in the invasion and metastasis through the Wnt/β-catenin pathway. It does so by direct methylation of β-catenin. This novel SETDB1/Wnt/β-catenin pathway provides a new strategy for the treatment of colorectal cancer.

Epigenetic regulation of SMAD3 by histone methyltransferase SMYD2 promotes lung cancer metastasis

Epigenetic alterations, especially histone methylation, are key factors in cell migration and invasion in cancer metastasis. However, in lung cancer metastasis, the mechanism by which histone methylation regulates metastasis has not been fully elucidated. Here, we found that the histone methyltransferase SMYD2 is overexpressed in lung cancer and that knockdown of SMYD2 could reduce the rates of cell migration and invasion in lung cancer cell lines via direct downregulation of SMAD3 via SMYD2-mediated epigenetic regulation. Furthermore, using an in vitro epithelial-mesenchymal transition (EMT) system with a Transwell system, we generated highly invasive H1299 (In-H1299) cell lines and observed the suppression of metastatic features by SMYD2 knockdown. Finally, two types of in vivo studies revealed that the formation of metastatic tumors by shSMYD2 was significantly suppressed. Thus, we suggest that SMYD2 is a potential metastasis regulator and that the development of SMYD2-specific inhibitors may help to increase the efficacy of lung cancer treatment.

SMYD2 Regulates Vascular Smooth Muscle Cell Phenotypic Switching and Intimal Hyperplasia via Interaction with Myocardin

The SET and MYND domain-containing protein 2 (SMYD2) is a histone lysine methyltransferase that has been reported to regulate carcinogenesis and inflammation. However, its role in vascular smooth muscle cell (VSMC) homeostasis and vascular diseases has not been determined. Here, we investigated the role of SMYD2 in VSMC phenotypic modulation and vascular intimal hyperplasia and elucidated the underlying mechanism. We observed that SMYD2 expression was downregulated in injured carotid arteries in mice and phenotypically modulated VSMCs in vitro. Using a SMC-specific Smyd2 knockout mouse model, we found that Smyd2 ablation in VSMCs exacerbates neointima formation after vascular injury in vivo. Conversely, Smyd2 overexpression inhibits VSMC proliferation and migration in vitro and attenuates arterial narrowing in injured vessels in mice. Smyd2 downregulation promotes VSMC phenotypic switching accompanied with enhanced proliferation and migration. Mechanistically, genome-wide transcriptome analysis and loss/gain-of-function studies revealed that SMYD2 up-regulates VSMC contractile gene expression and suppresses VSMC proliferation and migration, in part, by promoting expression and transactivation of the master transcription cofactor myocardin. In addition, myocardin directly interacts with SMYD2, thereby facilitating SMYD2 recruitment to the CArG regions of SMC contractile gene promoters and leading to an open chromatin status around SMC contractile gene promoters via SMYD2-mediated H3K4 methylation. Hence, we conclude that SMYD2 is a novel regulator of VSMC contractile phenotype and intimal hyperplasia via a myocardin-dependent epigenetic regulatory mechanism and may be a potential therapeutic target for occlusive vascular diseases.

Modification of Phosphorylation Sites in the Yeast Lysine Methyltransferase Set5 Exerts Influences on the Mitogen-Activated Protein Kinase Hog1 under Prolonged Acetic Acid Stress

Responses to acetic acid toxicity in the budding yeast Saccharomyces cerevisiae have widespread implications in the biorefinery of lignocellulosic biomass and food preservation. Our previous studies revealed that Set5, the yeast lysine methyltransferase and histone H4 methyltransferase, was involved in acetic acid stress tolerance. However, it is still mysterious how Set5 functions and interacts with the known stress signaling network. Here, we revealed that elevated phosphorylation of Set5 during acetic acid stress is accompanied by enhanced expression of the mitogen-activated protein kinase (MAPK) Hog1. Further experiments uncovered that the phosphomimetic mutation of Set5 endowed yeast cells with improved growth and fermentation performance and altered transcription of specific stress-responsive genes. Intriguingly, Set5 was found to bind the coding region of HOG1 and regulate its transcription, along with increased expression and phosphorylation of Hog1. A protein-protein interaction between Set5 and Hog1 was also revealed. In addition, modification of Set5 phosphosites was shown to regulate reactive oxygen species (ROS) accumulation, which is known to affect yeast acetic acid stress tolerance. The findings in this study imply that Set5 may function together with the central kinase Hog1 to coordinate cell growth and metabolism in response to stress. IMPORTANCE Hog1 is the yeast homolog of p38 MAPK in mammals that is conserved across eukaryotes, and it plays crucial roles in stress tolerance, fungal pathogenesis, and disease treatments. Here, we provide evidence that modification of Set5 phosphorylation sites regulates the expression and phosphorylation of Hog1, which expands current knowledge on upstream regulation of the Hog1 stress signaling network. Set5 and its homologous proteins are present in humans and various eukaryotes. The newly identified effects of Set5 phosphorylation site modifications in this study benefit an in-depth understanding of eukaryotic stress signaling, as well as the treatment of human diseases.

SETDB1 Modulates Degradation of Phosphorylated RB and Anticancer Efficacy of CDK4/6 Inhibitors

Retinoblastoma (RB) protein can exert tumor suppressor functions even when it becomes phosphorylated. It is thus essential to understand how phosphorylated RB (p-RB) expression and function are regulated. Here, we demonstrated that RING finger domain protein TRIM28 bound and promoted ubiquitination and degradation of CDK4/6-phosphorylated RB protein. SETDB1, a known TRIM28 binding partner, protected p-RB from degradation through the binding of methylated RB by its Tudor domain independent of its methyltransferase activity. SETDB1 was found to be frequently overexpressed due to gene amplification and positively correlated with p-RB in prostate cancer patient specimens. Inhibition of SETDB1 expression using a gene-specific antisense oligonucleotide (ASO) reduced tumor growth but accelerated RB protein degradation, limiting the therapeutic efficacy. However, coadministration of the CDK4/6 inhibitor palbociclib blocked ASO-induced RB degradation and resulted in a much greater cancer-inhibitory effect than each inhibitor alone both in vitro and in vivo. This study identified CDK4/6-dependent, TRIM28-mediated proteasomal degradation as a mechanism of RB inactivation and reveals SETDB1 as a key inhibitor of this process. Our findings suggest that combined targeting of SETDB1 and CDK4/6 represents a viable approach for the treatment of cancers with SETDB1 gene amplification or overexpression.

SIGNIFICANCE

The identification of a role for TRIM28 and SETDB1 in regulating CDK4/6-phosphorylated RB stability uncovers a combination strategy using CDK4/6 and SETDB1 inhibition to decrease RB degradation and inhibit cancer growth.

Targeting SMYD2 inhibits angiogenesis and increases the efficiency of apatinib by suppressing EGFL7 in colorectal cancer

Angiogenesis is an essential factor affecting the occurrence and development of solid tumors. SET And MYND Domain Containing 2 (SMYD2) serves as an oncogene in various cancers. However, whether SMYD2 is involved in tumor angiogenesis remains unclear. Here, we report that SMYD2 expression is associated with microvessel density in colorectal cancer (CRC) tissues. SMYD2 promotes CRC angiogenesis in vitro and in vivo. Mechanistically, SMYD2 physically interacts with HNRNPK and mediates lysine monomethylation at K422 of HNRNPK, which substantially increases RNA binding activity. HNRNPK acts by binding and stabilizing EGFL7 mRNA. As an angiogenic stimulant, EGFL7 enhances CRC angiogenesis. H3K4me3 maintained by PHF8 mediates the abnormal overexpression of SMYD2 in CRC. Moreover, targeting SMYD2 blocks CRC angiogenesis in tumor xenografts. Treatment with BAY-598, a functional inhibitor of SMYD2, can also synergize with apatinib in patient-derived xenografts. Overall, our findings reveal a new regulatory axis of CRC angiogenesis and provide a potential strategy for antiangiogenic therapy.

SMYD2 Promotes Hepatocellular Carcinoma Progression by Reprogramming Glutamine Metabolism via c-Myc/GLS1 Axis

Metabolic reprogramming, such as alterations in glutamine metabolism or glycolysis, is the hallmark of hepatocellular carcinoma (HCC). However, the underlying mechanisms are still incompletely elucidated. Previous studies have identified that methyltransferase SET and MYND domain-containing protein 2(SMYD2) is responsible for the pathogenesis of numerous types of cancer. Here, we innovatively uncover how SMYD2 regulates glutamine metabolism in HCC cells and promotes HCC progression. We identified that SMYD2 expression is upregulated in HCC tissues, which correlates with unfavorable clinical outcomes. Our in vitro and in vivo results showed that the depletion of SMYD2 inhibits HCC cell growth. Mechanistically, c-Myc methylation by SMYD2 increases its protein stability through the ubiquitin-proteasome system. We showed SMYD2 depletion destabilized c-Myc protein by increasing the conjugated K48-linked polyubiquitin chain. SMYD2 increased c-Myc expression and further upregulated glutaminase1 (GLS1), a crucial enzyme that catalyzes the conversion of glutamine to glutamic acid, in HCC cells. GLS1 plays an important role in SMYD2-mediated HCC progression and glutamine metabolism regulation. The knockdown of SMYD2 inhibited glutamine metabolism in HCC cells and overcame their chemoresistance to sorafenib. Collectively, our findings demonstrated a novel mechanism of how SMYD2 promotes HCC progression by regulating glutamine metabolism through the c-Myc/GLS1signaling, implicating the therapeutic potential of targeting SMYD2 in HCC patients.

Clinical prognostic value of the SMYD2/3 as new epigenetic biomarkers in solid cancer patients: a systematic review and meta-analysis

BACKGROUND

SET and MYND domain-containing protein (SMYD) family with methyltransferase activity is involved in cancer progression. This novel meta-analysis aimed to evaluate the association of SMYD family with the clinical and survival outcomes in solid cancer patients.

METHODS

We systematically searched Embase, PubMed, Scopus and Web of Science to select relevant articles. Hazard ratios (HRs), odds ratios (ORs), and 95% confidence intervals were extracted. Heterogeneity was evaluated by chi-square-based Q and I2 tests, while publication bias by funnel plots and Egger's test.

RESULTS

Thirty-two articles (4,826 patients) met inclusion criteria. SMYD2/3 overexpression was statistically associated with poor overall survival (HR = 1.794, P < 0.001), disease/relapse/progression-free survival (HR = 2.114, P < 0.001), disease/cancer-specific survival (HR = 3.220, P = 0.003), larger tumor size (OR = 1.963, P < 0.001), advanced TNM stage (OR = 2.066, P < 0.001), lymph node metastasis (OR = 2.054, P < 0.001), and distant metastasis (OR = 1.978, P = 0.004). Subgroup analysis showed more significant association between SMYD2 overexpression and reduced survival outcomes than that in SMYD3. Conversely, the relationship between SMYD3 and various clinicopathologic factors was stronger compared to SMYD2.

CONCLUSION

Enhanced SMYD2/3 expression may be an unfavorable clinical prognostic factor in different solid cancer types.

Effect of miRNA-200b on the proliferation of liver cancer cells via targeting SMYD2/p53 signaling pathway

OBJECTIVES

Our previous study has verified that high level of SET and MYND domain-containing protein 2 (SMYD2) plays an important role in acquiring aggressive ability for liver cancer cells in hepatocellular carcinoma. MiR-200b as a tumor suppressor gene involves in a variety of cancers. This study aims to investigate the correlation between miR-200b and SMYD2 in hepatocellular carcinoma and the underlying mechanism.

METHODS

Firstly, the levels of SMYD2 and miR-200b in hepatocellular carcinoma tissues and matched adjacent non-tumor liver tissues were tested with real-time reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. Secondly, we evaluated the interaction between miR-200b and SMYD2 using dual-luciferase reporter assay. Thirdly, we elucidated the effect of miR-200b on SMYD2 and its downstream targets p53/CyclinE1. Finally, we silenced SMYD2 in hepatocellular carcinoma cell lines to investigate its effect on tumor proliferation and cell cycle progression, and further confirmed the correlation among SMYD2 and p53/CyclinE1.

RESULTS

Compared with the matched adjacent non-tumor liver tissues, miR-200b was obviously decreased, and SMYD2 was significantly increased in hepatocellular carcinoma (both P<0.05). Spearman's rank correlation revealed that miR-200b expression was negatively correlated with SMYD2 (P<0.01). Computer algorithm and dual-luciferase reporter assay revealed that miR-200b directly targeted and suppressed SMYD2 in HEK 293T cells. The down-regulated miR-200b expression promoted hepatoma cell proliferation (P<0.05) and increased SMYD2 expression(P<0.01), while the up-regulated expression of miR-200b had an opposite effect. The knockdown of SMYD2 suppressed the proliferation of MHCC-97L cells (P<0.01), down-regulated CyclinE1, and up-regulated p53 expression (both P<0.05).

CONCLUSIONS

MiR-200b is involved in hepatocellular carcinoma progression via targeting SMYD2 and regulating SMYD2/p53/CyclinE1 signaling pathway and may be used as a potential target for hepatocellular carcinoma treatment.

The EEF1AKMT3/MAP2K7/TP53 axis suppresses tumor invasiveness and metastasis in gastric cancer

The importance of methylation in the tumorigenic responses of nonhistone proteins, such as TP53, PTEN, RB1, AKT, and STAT3, has been emphasized in numerous studies. In parallel, the corresponding nonhistone protein methyltransferases have been acknowledged in the pathophysiology of cancer. Thus, this study aimed to explore the pathological role of a nonhistone methyltransferase in gastric cancer (GC), identify nonhistone substrate protein, and understand the underlying mechanism. Interestingly, among the 24 methyltransferases and methyltransferase family 16 (MTF16) proteins, EEF1AKMT3 (METTL21B) expression was prominently lower in GC tissues than in normal adjacent tissues and was associated with a worse prognosis. In addition, EEF1AKMT3-knockdown induced gastric tumor invasiveness and migration. Through gain and loss-of-function studies, mass spectrometry analysis, RNA-seq, and phospho-antibody array, we identified EEF1AKMT3 as a novel tumor-suppressive methyltransferase that catalyzes the monomethylation of MAP2K7 (MKK7) at K296, thereby decreasing the phosphorylation, ubiquitination, and degradation of TP53. Furthermore, EEF1AKMT3, p-MAP2K7, and TP53 protein levels were positively correlated in GC tissues. Collectively, our results delineate the tumor-suppressive function of the EEF1AKMT3/MAP2K7/TP53 signaling axis and suggest the dysregulation of the signaling axis as potential targeted therapy in GC.

STUB1-SMYD2 Axis Regulates Drug Resistance in Glioma cells

SET and MYND domain-containing protein 2 (SMYD2) is an important epigenetic regulator that methylates histone and non-histone proteins. The study aimed to investigate the oncogenic role of SMYD2 in gliomas and explore its degradation mechanism induced by cisplatin. Tumor tissue microarray of 441 patients with glioma was collected for SMYD2 immunohistochemical staining. Kaplan-Meier survival curves were constructed using the overall survival values. mRNA-sequencing analysis was performed for understanding the downstream mechanisms mediated by SMYD2. The half-inhibitory concentrations (IC50) of temozolomide and cisplatin in AZ505-treated and control cells were calculated. The potential E3 ubiquitin ligase of SMYD2 was predicted in UbiBrowser and confirmed by a knockdown test. The effect of SMYD2 and its E3 ligase on apoptosis and migration of glioma cells was determined via cell-function assays. High SMYD2 expression correlated with a high WHO stage (P = 0.004) and a low survival probability (P = 0.012). The inhibition of SMYD2 suppressed the process of epithelial to mesenchymal transition (EMT) by downregulating the expression of Collagen 1A1 (COL1A1). AZ505 treatment significantly increased the drug sensitivity of glioma cells. SMYD2 expression was markedly reduced by cisplatin treatment via STIP1 Homology And U-Box Containing Protein 1 (STUB1)-mediated degradation. The knockdown of STUB1 could partly reverse the cell function impairment induced by cisplatin. Our findings suggested that SMYD2 could be a potential drug target for the treatment of gliomas, and STUB1-mediated degradation of SMYD2 plays an important role in reversing chemotherapy resistance in patients with gliomas.

Mechanistic and functional extrapolation of SET and MYND domain-containing protein 2 to pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal neoplasms worldwide and represents the vast majority of pancreatic cancer cases. Understanding the molecular pathogenesis and the underlying mechanisms involved in the initiation, maintenance, and progression of PDAC is an urgent need, which may lead to the development of novel therapeutic strategies against this deadly cancer. Here, we review the role of SET and MYND domain-containing protein 2 (SMYD2) in initiating and maintaining PDAC development through methylating multiple tumor suppressors and oncogenic proteins. Given the broad substrate specificity of SMYD2 and its involvement in diverse oncogenic signaling pathways in many other cancers, the mechanistic extrapolation of SMYD2 from these cancers to PDAC may allow for developing new hypotheses about the mechanisms driving PDAC tumor growth and metastasis, supporting a proposition that targeting SMYD2 could be a powerful strategy for the prevention and treatment of PDAC.

RNF2 mediates pulmonary fibroblasts activation and proliferation by regulating mTOR and p16-CDK4-Rb1 signaling pathway

BACKGROUND

Pulmonary fibrosis (PF) is a chronic, progressive interstitial lung disease with unknown etiology, associated with increasing morbidity and pessimistic prognosis. Pulmonary fibroblasts (PFbs) are the key effector cells of PF, in which abnormal activation and proliferation is an important pathogenesis of PF. Ring finger protein 2 (RNF2), is identified as the catalytic subunit of poly-comb repressive complex 1, which is closely related to occurrence and development of lung cancer, but its function in PF has not been revealed. In this paper, we sought to identify the regulatory role of RNF2 in lung fibrogenesis and its underlying mechanisms.

METHODS

The expression of RNF2 in lung fibrosis tissue (human and Bleomycin-induced mouse) and cell model (TGF-β1-induced HFL1 cells) was examined by immunoblotting analysis and immunofluorescence. Western blot, qRT-PCR were performed to evaluate the expression of pro-fibrogenic cytokines (including α-SMA, ECM and MMPs/ TIMPs) induced by TGF-β1 in HFL1 cells. Cell proliferation, cycle progression and apoptosis were examined by fow cytometric. Molecular interactions were tested by Co-IP assays.

RESULTS

RNF2 expression was elevated in PF tissues compared to normal adjacent tissues and in PFbs (HFL1) induced by TGF-β1. Furthermore, knockdown of RNF2 could evidently inhibit the abnormal expression of pro-fibrogenic cytokines (including α-SMA, ECM and MMPs/TIMPs) induced by TGF-β1 in HFL1 cells. Functionally, RNF2 silencing could significantly suppress TGF-β1-induced anomalous proliferation, cell cycle progression, apoptosis and autophagy in HFL1 cells. Mechanistically, RNF2 deficiency could effectively inhibit the abnormal activation of mTOR signaling pathway in TGF-β1-induced HFL1 cells, and mTOR pathway had feedback regulation on the expression of RNF2. Further studies RNF2 could regulate the phosphorylation level of RB1 through interacting with p16 to destroy the binding of p16 and CDK4 competitively. Simultaneously, overexpression of RNF2 could show the opposite results.

CONCLUSIONS

These results indicated that RNF2 is a potent pro-fibrogenic molecule for PFbs activation and proliferation through mTOR and p16-CDK4-Rb signaling pathways, and RNF2 inhibition will be a potential therapeutic avenue for treating PF.

Protein Lysine Methyltransferase SMYD2: A Promising Small Molecule Target for Cancer Therapy

In epigenetic research, the abnormality of protein methylation modification is closely related to the occurrence and development of tumors, which stimulates the interest of researchers in protein methyltransferase research and the efforts to develop corresponding specific small molecule inhibitors. Currently, the protein lysine methyltransferase SMYD2 has been identified as a promising new small molecule target for cancer therapy. But its biological functions have not been fully studied and relatively few inhibitors have been reported, thus this field needs to be further explored. This perspective provides a comprehensive and systematic review of the available resources in this field, including its research status, biological structure, related substrates and methylation mechanisms, and research status of inhibitors. In addition, this perspective elaborates in detail the current challenges in this field, our insights into what needs to be done next, rational drug design of novel SMYD2 inhibitors, and foreseeable development directions in the future.

Oleocanthal Attenuates Metastatic Castration-Resistant Prostate Cancer Progression and Recurrence by Targeting SMYD2

Simple Summary

The Mediterranean, extra-virgin-olive-oil-rich diet ingredient S-(-)-oleocanthal (OC) has emerged as a potential inhibitor for the growth and relapse of the most aggressive prostate cancer type. This effect is mediated through suppression of important enzyme, SMYD2, that drives the activation of several downstream protein effectors. OC treatments reduced SMYD2 downstream substrates, which are critical for prostate cancer growth and relapse. OC is more advantageous than other reported SMYD2 inhibitors because it has shown potent anticancer activity in animal models. OC’s anti-prostate-cancer effect was prominent compared with some standard drugs currently used to control prostate cancer. OC is a potential, novel natural compound appropriate for immediate use by prostate cancer patients and survivors as a nutraceutical or dietary supplement product.

Abstract

Metastatic castration-resistant prostate cancer (mCRPC) is the most aggressive prostate cancer (PC) phenotype. Cellular lysine methylation is driven by protein lysine methyltransferases (PKMTs), such as those in the SET- and MYND-containing protein (SMYD) family, including SMYD2 methylate, and several histone and non-histone proteins. SMYD2 is dysregulated in metastatic PC patients with high Gleason score and shorter survival. The Mediterranean, extra-virgin-olive-oil-rich diet ingredient S-(-)-oleocanthal (OC) inhibited SMYD2 in biochemical assays and suppressed viability, migration, invasion, and colony formation of PC-3, CWR-R1ca, PC-3M, and DU-145 PC cell lines with IC₅₀ range from high nM to low µM. OC’s in vitro antiproliferative effect was comparable to standard anti-PC chemotherapies or hormone therapies. A daily, oral 10 mg/kg dose of OC for 11 days effectively suppressed the progression of the mCRPC CWR-R1ca cells engrafted into male nude mice. Daily, oral OC treatment for 30 days suppressed tumor locoregional and distant recurrences after the primary tumors’ surgical excision. Collected OC-treated animal tumors showed marked SMYD2 reduction. OC-treated mice showed significant serum PSA reduction. For the first time, this study showed SMYD2 as novel molecular target in mCRPC, and OC emerged as a specific SMYD2 lead inhibitor. OC prevailed over previously reported SMYD2 inhibitors, with validated in vivo potency and high safety profile, and, therefore, is proposed as a novel nutraceutical for mCRPC progression and recurrence control.

Molecular Mechanisms of Epigenetic Regulation, Inflammation, and Cell Death in ADPKD

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder, which is caused by mutations in the PKD1 and PKD2 genes, characterizing by progressive growth of multiple cysts in the kidneys, eventually leading to end-stage kidney disease (ESKD) and requiring renal replacement therapy. In addition, studies indicate that disease progression is as a result of a combination of factors. Understanding the molecular mechanisms, therefore, should facilitate the development of precise therapeutic strategies for ADPKD treatment. The roles of epigenetic modulation, interstitial inflammation, and regulated cell death have recently become the focuses in ADPKD. Different epigenetic regulators, and the presence of inflammatory markers detectable even before cyst growth, have been linked to cyst progression. Moreover, the infiltration of inflammatory cells, such as macrophages and T cells, have been associated with cyst growth and deteriorating renal function in humans and PKD animal models. There is evidence supporting a direct role of the PKD gene mutations to the regulation of epigenetic mechanisms and inflammatory response in ADPKD. In addition, the role of regulated cell death, including apoptosis, autophagy and ferroptosis, have been investigated in ADPKD. However, there is no consensus whether cell death promotes or delays cyst growth in ADPKD. It is therefore necessary to develop an interactive picture between PKD gene mutations, the epigenome, inflammation, and cell death to understand why inherited PKD gene mutations in patients may result in the dysregulation of these processes that increase the progression of renal cyst formation.

Functions and Interactions of Mammalian KDM5 Demethylases

Mammalian histone demethylases of the KDM5 family are mediators of gene expression dynamics during developmental, cellular differentiation, and other nuclear processes. They belong to the large group of JmjC domain containing, 2-oxoglutarate (2-OG) dependent oxygenases and target methylated lysine 4 of histone H3 (H3K4me1/2/3), an epigenetic mark associated with active transcription. In recent years, KDM5 demethylases have gained increasing attention due to their misregulation in many cancer entities and are intensively explored as therapeutic targets. Despite these implications, the molecular basis of KDM5 function has so far remained only poorly understood. Little is known about mechanisms of nucleosome recognition, the recruitment to genomic targets, as well as the local regulation of demethylase activity. Experimental evidence suggests close physical and functional interactions with epigenetic regulators such as histone deacetylase (HDAC) containing complexes, as well as the retinoblastoma protein (RB). To understand the regulation of KDM5 proteins in the context of chromatin, these interactions have to be taken into account. Here, we review the current state of knowledge on KDM5 function, with a particular emphasis on molecular interactions and their potential implications. We will discuss and outline open questions that need to be addressed to better understand histone demethylation and potential demethylation-independent functions of KDM5s. Addressing these questions will increase our understanding of histone demethylation and allow us to develop strategies to target individual KDM5 enzymes in specific biological and disease contexts.

Chromatin Methylation Abnormalities in Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease worldwide and is one of the major causes of end-stage renal disease. PKD1 and PKD2 are two genes that mainly contribute to the development and progression of ADPKD. The precise mechanism is not fully understood. In recent years, epigenetic modification has drawn increasing attention. Chromatin methylation is a very important category of PKD epigenetic changes and mostly involves DNA, histone, and RNA methylation. Genome hypomethylation and regional gene hypermethylation coexist in ADPKD. We found that the genomic DNA of ADPKD kidney tissues showed extensive demethylation by whole-genome bisulphite sequencing, while some regional DNA methylation from body fluids, such as blood and urine, can be used as diagnostic or prognostic biomarkers to predict PKD progression. Histone modifications construct the histone code mediated by histone methyltransferases and contribute to aberrant methylation changes in PKD. Considering the complexity of methylation abnormalities occurring in different regions and genes on the PKD epigenome, more specific therapy aiming to restore to the normal genome should lead to the development of epigenetic treatment.

Post-translational modifications on the retinoblastoma protein

The retinoblastoma protein (pRb) functions as a cell cycle regulator controlling G1 to S phase transition and plays critical roles in tumour suppression. It is frequently inactivated in various tumours. The functions of pRb are tightly regulated, where post-translational modifications (PTMs) play crucial roles, including phosphorylation, ubiquitination, SUMOylation, acetylation and methylation. Most PTMs on pRb are reversible and can be detected in non-cancerous cells, playing an important role in cell cycle regulation, cell survival and differentiation. Conversely, altered PTMs on pRb can give rise to anomalies in cell proliferation and tumourigenesis. In this review, we first summarize recent findings pertinent to how individual PTMs impinge on pRb functions. As many of these PTMs on pRb were published as individual articles, we also provide insights on the coordination, either collaborations and/or competitions, of the same or different types of PTMs on pRb. Having a better understanding of how pRb is post-translationally modulated should pave the way for developing novel and specific therapeutic strategies to treat various human diseases.

Protein Methylation in Diabetic Kidney Disease

Chronic kidney disease (CKD) is defined by persistent urine aberrations, structural abnormalities, or impaired excretory renal function. Diabetes is the leading cause of CKD. Their common pathological manifestation is renal fibrosis. Approximately half of all patients with type 2 diabetes and one-third with type 1 diabetes will develop CKD. However, renal fibrosis mechanisms are still poorly understood, especially post-transcriptional and epigenetic regulation. And an unmet need remains for innovative treatment strategies for preventing, arresting, treating, and reversing diabetic kidney disease (DKD). People believe that protein methylation, including histone and non-histone, is an essential type of post-translational modification (PTM). However, prevalent reviews mainly focus on the causes such as DNA methylation. This review will take insights into the protein part. Furthermore, by emphasizing the close relationship between protein methylation and DKD, we will summarize the clinical research status and foresee the application prospect of protein methyltransferase (PMT) inhibitors in DKD treatment. In a nutshell, our review will contribute to a more profound understanding of DKD’s molecular mechanism and inspire people to dig into this field.

SMYD2 Inhibition Downregulates TMPRSS2 and Decreases SARS-CoV-2 Infection in Human Intestinal and Airway Epithelial Cells

The COVID-19 pandemic caused by SARS-CoV-2 has lasted for more than two years. Despite the presence of very effective vaccines, the number of virus variants that escape neutralizing antibodies is growing. Thus, there is still a need for effective antiviral treatments that target virus replication independently of the circulating variant. Here, we show for the first time that deficiency or pharmacological inhibition of the cellular lysine-methyltransferase SMYD2 decreases TMPRSS2 expression on both mRNA and protein levels. SARS-CoV-2 uses TMPRSS2 for priming its spike protein to infect target cells. Treatment of cultured cells with the SMYD2 inhibitors AZ505 or BAY598 significantly inhibited viral replication. In contrast, treatment of Vero E6 cells, which do not express detectable amounts of TMPRSS2, had no effect on SARS-CoV-2 infection. Moreover, by generating a recombinant reporter virus that expresses the spike protein of the Delta variant of SARS-CoV-2, we demonstrate that BAY598 exhibits similar antiviral activity against this variant of concern. In summary, SMYD2 inhibition downregulates TMPRSS2 and blocks viral replication. Targeting cellular SMYD2 represents a promising tool to curtail SARS-CoV-2 infection.

Protein post-translational modifications in the regulation of cancer hallmarks

Posttranslational modifications (PTMs) of proteins, the major mechanism of protein function regulation, play important roles in regulating a variety of cellular physiological and pathological processes. Although the classical PTMs, such as phosphorylation, acetylation, ubiquitination and methylation, have been well studied, the emergence of many new modifications, such as succinylation, hydroxybutyrylation, and lactylation, introduces a new layer to protein regulation, leaving much more to be explored and wide application prospects. In this review, we will provide a broad overview of the significant roles of PTMs in regulating human cancer hallmarks through selecting a diverse set of examples, and update the current advances in the therapeutic implications of these PTMs in human cancer.

Retinoblastoma Protein Paralogs and Tumor Suppression

The retinoblastoma susceptibility gene (RB1) is the first tumor suppressor gene discovered and a prototype for understanding regulatory networks that function in opposition to oncogenic stimuli. More than 3 decades of research has firmly established a widespread and prominent role for RB1 in human cancer. Yet, this gene encodes but one of three structurally and functionally related proteins that comprise the pocket protein family. A central question in the field is whether the additional genes in this family, RBL1 and RBL2, are important tumor suppressor genes. If so, how does their tumor suppressor activity overlap or differ from RB1. Here we revisit these questions by reviewing relevant data from human cancer genome sequencing studies that have been rapidly accumulating in recent years as well as pertinent functional studies in genetically engineered mice. We conclude that RBL1 and RBL2 do have important tumor suppressor activity in some contexts, but RB1 remains the dominant tumor suppressor in the family. Given their similarities, we speculate on why RB1 tumor suppressor activity is unique.

Histone methyltransferase Smyd2 contributes to blood-brain barrier breakdown in stroke

BACKGROUND

The blood-brain barrier (BBB) plays a principal role in the healthy and diseased central nervous systems, and BBB disruption after ischaemic stroke is responsible for increased mortality. Smyd2, a member of the SMYD-methyltransferase family, plays a vital role in disease by methylation of diverse substrates; however, little is known about its role in the pathophysiology of the brain in response to ischaemia-reperfusion injury.

METHODS

Using oxygen glucose deprivation and reoxygenation (OGD/R)-induced primary brain microvascular endothelial cells (BMECs) and Smyd2 knockdown mice subjected to middle cerebral artery occlusion, we evaluated the role of Smyd2 in BBB disruption. We performed loss-of-function and gain-of-function studies to investigate the biological function of Smyd2 in ischaemic stroke.

RESULTS

We found that Smyd2 was a critical factor for regulating brain endothelial barrier integrity in ischaemia-reperfusion injury. Smyd2 is upregulated in peri-ischaemic brains, leading to BBB disruption via methylation-mediated Sphk/S1PR. Knockdown of Smyd2 in mice reduces BBB permeability and improves functional recovery. Using OGD/R-induced BMECs, we demonstrated that Sphk/S1PR methylation modification by Smyd2 affects ubiquitin-dependent degradation and protein stability, which may disrupt endothelial integrity. Moreover, overexpression of Smyd2 can damage endothelial integrity through Sphk/S1PR signalling.

CONCLUSIONS

Overall, these results reveal a novel role for Smyd2 in BBB disruption in ischaemic stroke, suggesting that Smyd2 may represent a new therapeutic target for ischaemic stroke.

How Protein Methylation Regulates Steroid Receptor Function

Steroid receptors (SRs) are members of the nuclear hormonal receptor family, many of which are transcription factors regulated by ligand binding. SRs regulate various human physiological functions essential for maintenance of vital biological pathways, including development, reproduction, and metabolic homeostasis. In addition, aberrant expression of SRs or dysregulation of their signaling has been observed in a wide variety of pathologies. SR activity is tightly and finely controlled by post-translational modifications (PTMs) targeting the receptors and/or their coregulators. Whereas major attention has been focused on phosphorylation, growing evidence shows that methylation is also an important regulator of SRs. Interestingly, the protein methyltransferases depositing methyl marks are involved in many functions, from development to adult life. They have also been associated with pathologies such as inflammation, as well as cardiovascular and neuronal disorders, and cancer. This article provides an overview of SR methylation/demethylation events, along with their functional effects and biological consequences. An in-depth understanding of the landscape of these methylation events could provide new information on SR regulation in physiology, as well as promising perspectives for the development of new therapeutic strategies, illustrated by the specific inhibitors of protein methyltransferases that are currently available.

Effects of the Lysine Methyltransferase Inhibitor AZ505 on Bone Metabolism

Background

Protein methylation has important role in regulating diverse cellular responses, including differentiation, by affecting protein activity, stability, and interactions. AZ505 is an inhibitor of the SET and MYND domain-containing protein 2 lysine methylase. In this study, we investigated the effect of AZ505 on osteoblast and osteoclast differentiation in vitro and evaluated the effect of AZ505 in vivo on the long bones in mice.

Methods

Osteoblast differentiation was assessed by alkaline phosphatase (ALP) and Alizarin red staining after culturing calvarial preosteoblasts in an osteogenic medium. Osteoclast differentiation was analyzed by tartrate-resistant acid phosphatase (TRAP) staining in bone marrow-derived macrophages cultured with macrophage-colony stimulating factor and receptor activator of nuclear factor-κB ligand (RANKL). For in vivo experiments, mice were intraperitoneally injected with AZ505 and femurs were examined by micro-computed tomography.

Results

AZ505 increased ALP and Alizarin red staining in cultured osteoblasts and the expression of osteoblast marker genes, including Runx2 and osteocalcin. AZ505 resulted in decreased TRAP-staining of osteoclasts and expression of c-Fos and nuclear factor of activated T cells transcription factors and osteoclast marker genes, including cathepsin K and dendritic cell-specific transmembrane protein. Unexpectedly, in vivo administration of AZ505 markedly decreased the trabecular bone mass of femurs. In support of this catabolic result, AZ505 strongly upregulated RANKL expression in osteoblasts.

Conclusions

The results indicate that AZ505 has a catabolic effect on bone metabolism in vivo despite its anabolic effect in bone cell cultures. The findings indicate that cell culture data should be extrapolated cautiously to in vivo outcomes for studying bone metabolism.

SMYD1 alleviates septic myocardial injury by inhibiting endoplasmic reticulum stress

Sepsis-induced cardiomyopathy (SIC) is a major complication of sepsis. SET and MYND domain containing 1 (SMYD1) has central importance in heart development, and its role in SIC has not been identified. Herein, we found that the expression of SMYD1 was downregulated in myocardial tissues of SIC patients (from GEO database: GSE79962) and lipopolysaccharide (LPS)-induced SIC rats, and LPS-induced H9c2 cardiomyocytes. We used LPS-stimulated H9c2 cells that mimic sepsis in vitro to explore the function of SMYD1 in SIC. MTT assay, LDH and CK-MB release assay, flow cytometry, and ELISA assay showed that SMYD1 overexpression enhanced cell viability, alleviated cell injury, impeded apoptosis, and reduced the level of proinflammatory factors and NF-κB activation under the condition of LPS stimulation. Moreover, SMYD1 exerted protective effect on H9c2 cells stimulated with LPS through relieving endoplasmic reticulum (ER) stress. In conclusion, overexpression of SMYD1 alleviates cardiac injury through relieving ER stress during sepsis.

Critical roles of SMYD2 lysine methyltransferase in mediating renal fibroblast activation and kidney fibrosis

SET and MYND domain protein 2 (SMYD2) is a lysine methyltransferase that mediates histone H3 lysine 36 trimethylation (H3K36me3) and acts as a regulator of tumorgenesis and cystic growth. However, its role in renal fibrosis remains unknown. In this study, we found that SMYD2 was highly expressed in the murine kidney of renal fibrosis induced by unilateral ureteral obstruction, and primarily located in interstitial fibroblasts and renal tubular epithelial cells. Pharmacological inhibition of SMYD2 with AZ505, a highly selective inhibitor of SMYD2, protected against renal fibrosis and inhibited activation/proliferation of renal interstitial fibroblasts and conversion of epithelial cells to a profibrotic phenotype in this model. In cultured renal interstitial fibroblasts, treatment with AZ505 or silencing of SMYD2 by specific siRNA also inhibited serum- or TGF-β1-induced activation and proliferation of renal interstitial fibroblasts. Mechanistic studies showed that SMYD2 inhibition reduced phosphorylation of several profibrotic signaling molecules, including Smad3, extracellular signal-regulated kinase 1/2, AKT, signal transducer and activator of transcription-3 and nuclear factor-κB in both injured kidney and cultured renal fibroblasts. AZ505 was also effective in suppressing renal expression of Snail and Twist, two transcriptional factors that mediate renal partial epithelial-mesenchymal transition and fibrosis. Conversely, AZ505 treatment prevented downregulation of Smad7, a renoprotective factor in vivo and in vitro. These results indicate that SMYD2 plays a critical role in mediating conversion of epithelial cells to a profibrotic phenotype, renal fibroblast activation and renal fibrogenesis, and suggest that SMYD2 may be a potential target for the treatment of chronic fibrosis in kidney disease.

SMYD2 suppresses p53 activity to promote glucose metabolism in cervical cancer

Reprogrammed energy metabolism, especially the Warburg effect, is emerged as a hallmark of cancer. The protein lysine methyltransferase SMYD2 functions as an oncogene and is implicated in various malignant phenotypes of human cancers. However, the role of SMYD2 in tumor metabolism is still largely unknown. Here, we report that SMYD2 is highly expressed in human cervical cancer and its aberrant expression is linked to a poor prognosis. Bioinformatic analysis revealed a novel link between SMYD2 expression and aerobic glycolysis. Through loss-of-function experiments, we demonstrated that SMYD2 knockdown or inhibition induced a metabolic shift from aerobic glycolysis to oxidative phosphorylation, as evidenced by glucose uptake, lactate production, extracellular acidification, and the oxygen consumption rate. In contrast, SMYD2 overexpression promoted glycolytic metabolism in cervical cancer cells. Moreover, SMYD2 was required for tumor growth in cervical cancer and this oncogenic activity was largely glycolysis-dependent. Mechanistically, SMYD2 altered the methylation status of p53 and inhibited its transcriptional activity. Genetic silencing of p53 largely abrogated the effects of SMYD2 in promoting aerobic glycolysis. Taken together, our findings reveal a novel function of SMYD2 in regulating the Warburg effect in cervical cancer.