Crystal Structure of MLL2 Complex Guides the Identification of a Methylation Site on P53 Catalyzed by KMT2 Family Methyltransferases

Recurrent mucinous carcinoma with sarcomatoid and sarcomatous mural nodules: a case report and literature review

Ovarian mucinous tumors with sarcomatous mural nodules are rare. Sarcomatous nodules have a bad prognosis. Its diagnosis and treatment are controversial.It is still controversial whether malignant mural nodules represent a dedifferentiated form of mucinous tumors or collisional tumors. This is a case report of a 32-year-old female diagnosed with ovarian mucinous tumor recurred as a mucinous carcinoma combined with sarcomatoid and undifferentiated sarcoma mural nodules after surgery and chemotherapy. The primary lesion did not have a sarcomatous component after comprehensive sampling and repeated review, while the recurrent lesion had a predominantly sarcomatous component. The patient received a second operation and postoperative chemotherapy plus Anlotinib with no progression at 16 months of follow-up. Primary mucinous carcinoma and sarcomatous mural nodules revealed the same K-RAS mutation(c.35G>T, pG12V), TP53 mutation (c.817C>T, p.R273C), MLL2 mutation(c.13450C>T, p.R4484) and NF1 mutation(c.7876A>G, p.S2626G). We present a comprehensive analysis on morphologic characteristics, molecular detection results, clinical management, and prognosis of ovarian mucinous tumors with mural nodules of sarcomatoid and undifferentiated sarcoma. Mutation sharing between primary mucinous carcinoma and recurrent sarcomatous nodules supports monoclonal origin of primary and recurrent tumors, suggesting a tendency for sarcomatous differentiation during the progression of epithelial tumors. Malignant mural nodules represent dedifferentiation in mucinous ovarian tumors rather than collision of two different tumor types. Therefore, it is imperative to conduct comprehensive sampling, rigorous clinical examination, and postoperative follow-up in order to thoroughly evaluate all mural nodules of ovarian mucinous tumors due to their potential for malignancy and sarcomatous differentiation.

Molecular insights of KMT2D and clinical aspects of Kabuki syndrome type 1

BACKGROUND

Kabuki syndrome type 1 (KS1), a rare multisystem congenital disorder, presents with characteristic facial features, intellectual disability, persistent fetal fingertip pads, skeletal abnormalities, and postnatal growth delays. KS1 results from pathogenic variants in the KMT2D gene, which encodes a histone methyltransferase protein involved in chromatin remodeling, promoter and enhancer regulation, and scaffold formation during early development. KMT2D also mediates cell signaling pathways, responding to external stimuli and organizing effector protein assembly. Research on KMT2D's molecular mechanisms in KS1 has primarily focused on its histone methyltransferase activity, leaving a gap in understanding the methyltransferase-independent roles in KS1 clinical manifestations.

METHODS

This scoping review examines KMT2D's role in gene expression regulation across various species, cell types, and contexts. We analyzed human pathogenic KMT2D variants using publicly available databases and compared them to research organism models of KS1. We also conducted a systematic search of healthcare and governmental databases for clinical trials, studies, and therapeutic approaches.

RESULTS

Our review highlights KMT2D's critical roles beyond methyltransferase activity in diverse cellular contexts and conditions. We identified six distinct groups of KMT2D as a cell signaling mediator, including evidence of methyltransferase-dependent and -independent activity. A comprehensive search of the literature, clinical databases, and public registries emphasizes the need for basic research on KMT2D's functional complexity and longitudinal studies of KS1 patients to establish objective outcome measurements for therapeutic development.

CONCLUSION

We discuss how KMT2D's role in translating external cellular communication can partly explain the clinical heterogeneity observed in KS1 patients. Additionally, we summarize the current molecular diagnostic approaches and clinical trials targeting KS1. This review is a resource for patient advocacy groups, researchers, and physicians to support KS1 diagnosis and therapeutic development.

Histone lysine methyltransferase-related neurodevelopmental disorders: current knowledge and saRNA future therapies

Neurodevelopmental disorders encompass a group of debilitating diseases presenting with motor and cognitive dysfunction, with variable age of onset and disease severity. Advances in genetic diagnostic tools have facilitated the identification of several monogenic chromatin remodeling diseases that cause Neurodevelopmental disorders. Chromatin remodelers play a key role in the neuro-epigenetic landscape and regulation of brain development; it is therefore not surprising that mutations, leading to loss of protein function, result in aberrant neurodevelopment. Heterozygous, usually de novo mutations in histone lysine methyltransferases have been described in patients leading to haploinsufficiency, dysregulated protein levels and impaired protein function. Studies in animal models and patient-derived cell lines, have highlighted the role of histone lysine methyltransferases in the regulation of cell self-renewal, cell fate specification and apoptosis. To date, in depth studies of histone lysine methyltransferases in oncology have provided strong evidence of histone lysine methyltransferase dysregulation as a determinant of cancer progression and drug resistance. As a result, histone lysine methyltransferases have become an important therapeutic target for the treatment of different cancer forms. Despite recent advances, we still lack knowledge about the role of histone lysine methyltransferases in neuronal development. This has hampered both the study and development of precision therapies for histone lysine methyltransferases-related Neurodevelopmental disorders. In this review, we will discuss the current knowledge of the role of histone lysine methyltransferases in neuronal development and disease progression. We will also discuss how RNA-based technologies using small-activating RNAs could potentially provide a novel therapeutic approach for the future treatment of histone lysine methyltransferase haploinsufficiency in these Neurodevelopmental disorders, and how they could be first tested in state-of-the-art patient-derived neuronal models.

KMT2B-dependent RFK transcription activates the TNF-α/NOX2 pathway and enhances ferroptosis caused by myocardial ischemia-reperfusion

Epigenetic regulation such as histone modification is implicated in the pathogenesis of myocardial ischemia/reperfusion injury (MIRI). Lysine-specific methyltransferase 2B (KMT2B) is a histone H3 lysine 4 (H3K4) methyltransferase. This study aims at exploring the role of KMT2B-mediated histone modification in MIRI. Peripheral blood samples were collected from 30 patients with acute myocardial infarction (AMI) and 30 healthy volunteers for analyses of the expression levels of KMT2B, riboflavin kinase (RFK), tumor necrosis factor (TNF)-α, and NADPH oxidase 2 (NOX2). H9C2 cardiomyocytes and Sprague-Dawley rats were utilized for developing in vitro and in vivo models. To evaluate the effects of the aforementioned molecules on cellular damage and MIRI, short hairpin RNAs or overexpression plasmids were introduced into cardiomyocytes for gene silencing or overexpression and also, they were packaged into adenovirus vectors for in vivo interventions. Immunoprecipitation assays were conducted to assess the interactions between KMT2B and RFK and among RFK, NOX2 sub-unit p22^phox, and TNF receptor 1-associated death domain protein. KMT2B, RFK, TNF-α, and NOX2 were notably upregulated in AMI patients. KMT2B knockdown resulted in considerably attenuated cell apoptosis and reduced myocardial infarct area. Additionally, the release of pro-inflammatory proteins and ferroptosis were suppressed. Furthermore, KMT2B could promote RFK gene transcription by upregulating H3 methylation levels and consequently activate the TNF-α/NOX2 axis, which was the possible mechanism underlying the role of KMT2B in MIRI. KMT2B motivates MIRI-induced cellular injury and ferroptosis by inducing RFK transcription and mediating the TNF-α/NOX2 axis.

Structural basis for product specificities of MLL family methyltransferases

Human mixed-lineage leukemia (MLL) family methyltransferases methylate histone H3 lysine 4 to different methylation states (me1/me2/me3) with distinct functional outputs, but the mechanism underlying the different product specificities of MLL proteins remains unclear. Here, we develop methodologies to quantitatively measure the methylation rate difference between mono-, di-, and tri-methylation steps and demonstrate that MLL proteins possess distinct product specificities in the context of the minimum MLL-RBBP5-ASH2L complex. Comparative structural analyses of MLL complexes by X-ray crystal structures, fluorine-19 nuclear magnetic resonance, and molecular dynamics simulations reveal that the dynamics of two conserved tyrosine residues at the "F/Y (phenylalanine/tyrosine) switch" positions fine-tune the product specificity. The variation in the intramolecular interaction between SET-N and SET-C affects the F/Y switch dynamics, thus determining the product specificities of MLL proteins. These results indicate a modified F/Y switch rule applicable for most SET domain methyltransferases and implicate the functional divergence of MLL proteins.

The apparent paradox of phenotypic diversity and shared mechanisms across dystonia syndromes

PURPOSE OF REVIEW

We describe here how such mechanisms shared by different genetic forms can give rise to motor performance dysfunctions with a clinical aspect of dystonia.

RECENT FINDINGS

The continuing discoveries of genetic causes for dystonia syndromes are transforming our view of these disorders. They share unexpectedly common underlying mechanisms, including dysregulation in neurotransmitter signaling, gene transcription, and quality control machinery. The field has further expanded to include forms recently associated with endolysosomal dysfunction.

SUMMARY

The discovery of biological pathways shared between different monogenic dystonias is an important conceptual advance in the understanding of the underlying mechanisms, with a significant impact on the pathophysiological understanding of clinical phenomenology. The functional relationship between dystonia genes could revolutionize current dystonia classification systems, classifying patients with different monogenic forms based on common pathways. The most promising effect of these advances is on future mechanism-based therapeutic approaches.

Histone-lysine N-methyltransferase 2 (KMT2) complexes - a new perspective

Histone H3 Lys4 (H3K4) methylation is catalyzed by the Histone-Lysine N-Methyltransferase 2 (KMT2) protein family, and its members are required for gene expression control. In vertebrates, the KMT2s function in large multisubunit complexes known as COMPASS or COMPASS-like complexes (COMplex of Proteins ASsociated with Set1). The activity of these complexes is critical for proper development, and mutation-induced defects in their functioning have frequently been found in human cancers. Moreover, inherited or de novo mutations in KMT2 genes are among the etiological factors in neurodevelopmental disorders such as Kabuki and Kleefstra syndromes. The canonical role of KMT2s is to catalyze H3K4 methylation, which results in a permissive chromatin environment that drives gene expression. However, current findings described in this review demonstrate that these enzymes can regulate processes that are not dependent on methylation: noncatalytic functions of KMT2s include DNA damage response, cell division, and metabolic activities. Moreover, these enzymes may also methylate non-histone substrates and play a methylation-dependent function in the DNA damage response. In this review, we present an overview of the new, noncanonical activities of KMT2 complexes in a variety of cellular processes. These discoveries may have crucial implications for understanding the functions of these methyltransferases in developmental processes, disease, and epigenome-targeting therapeutic strategies in the future.

Serological and Molecular Characterization of Hepatitis B Virus Infection in Gastric Cancer

Hepatitis B virus (HBV) infection has been reported to be associated with gastric cancer (GC). Nonetheless, no study has revealed the role of HBV infection in the survival of patients with GC, and the mutation profiles of HBV-infected patients with GC have never been documented. Here, we performed an updated meta-analysis and found a significantly increased risk of GC in HBV-infected individuals (sOR, 1.29; 95% CI, 1.22-1.37). Furthermore, we observed that in the Anhui area, the rate of serum HBsAg positivity (OR, 1.62; 95% CI, 1.03-2.55) was significantly higher in GC patients than in controls. Moreover, our results showed that HBV-positive patients had significantly worse disease-free survival (HR, 1.98; 95% CI, 1.39-2.82) and overall survival (HR, 1.84; 95% CI, 1.19-2.85) than HBV-negative patients. The results of Cox proportional hazards regression proved that HBV infection was an independent adverse prognostic factor in GC. Furthermore, by performing targeted-NGS, we found unique mutation profiles in HBV-infected GC samples, including five frequently mutated protein-coding genes (KMT2B, KMT2D, SOX1, FGF12, and TUBB2B). Expression and survival analyses of these genes identified three novel candidate genes that may have potential roles in GC development. Gene Ontology enrichment analysis showed that the recurrent mutations in HBV-positive GC samples were related to cell proliferation, cell migration, and transcription. Taking together, our study proved that HBV infection is an independent prognostic factor in GC patients. The unique mutation profiles of HBV-infected patients with GC open a new research direction toward the underling mechanism between HBV infection and GC.

Structure, Activity and Function of the MLL2 (KMT2B) Protein Lysine Methyltransferase

The Mixed Lineage Leukemia 2 (MLL2) protein, also known as KMT2B, belongs to the family of mammalian histone H3 lysine 4 (H3K4) methyltransferases. It is a large protein of 2715 amino acids, widely expressed in adult human tissues and a paralog of the MLL1 protein. MLL2 contains a characteristic C-terminal SET domain responsible for methyltransferase activity and forms a protein complex with WRAD (WDR5, RbBP5, ASH2L and DPY30), host cell factors 1/2 (HCF 1/2) and Menin. The MLL2 complex is responsible for H3K4 trimethylation (H3K4me3) on specific gene promoters and nearby cis-regulatory sites, regulating bivalent developmental genes as well as stem cell and germinal cell differentiation gene sets. Moreover, MLL2 plays a critical role in development and germ line deletions of Mll2 have been associated with early growth retardation, neural tube defects and apoptosis that leads to embryonic death. It has also been involved in the control of voluntary movement and the pathogenesis of early stage childhood dystonia. Additionally, tumor-promoting functions of MLL2 have been detected in several cancer types, including colorectal, hepatocellular, follicular cancer and gliomas. In this review, we discuss the main structural and functional aspects of the MLL2 methyltransferase with particular emphasis on transcriptional mechanisms, gene regulation and association with diseases.

Biochemical perspectives on targeting KMT2 methyltransferases in cancer

KMT2 methyltransferases are important regulators of gene transcription through the methylation of histone H3 lysine 4 at promoter and enhancer regions. They reside in large, multisubunit protein complexes, which not only regulate their catalytic activities but also mediate their interactions with chromatin. The KMT2 family was initially associated with cancer due to the discovery of KMT2A translocations in mixed-lineage leukemia (MLL). However, emerging evidences suggest that the methyltransferase activity of KMT2 enzymes can also be important in cancer, raising the prospect of targeting the catalytic domain of KMT2 as a therapeutic strategy. In this review, we summarize recent advances in our understanding of KMT2 enzyme mechanisms and their regulation on nucleosomes, which will provide mechanistic insights into therapeutic discoveries targeting their methyltransferase activities.

Aberrant Activity of Histone-Lysine N-Methyltransferase 2 (KMT2) Complexes in Oncogenesis

KMT2 (histone-lysine N-methyltransferase subclass 2) complexes methylate lysine 4 on the histone H3 tail at gene promoters and gene enhancers and, thus, control the process of gene transcription. These complexes not only play an essential role in normal development but have also been described as involved in the aberrant growth of tissues. KMT2 mutations resulting from the rearrangements of the KMT2A (MLL1) gene at 11q23 are associated with pediatric mixed-lineage leukemias, and recent studies demonstrate that KMT2 genes are frequently mutated in many types of human cancers. Moreover, other components of the KMT2 complexes have been reported to contribute to oncogenesis. This review summarizes the recent advances in our knowledge of the role of KMT2 complexes in cell transformation. In addition, it discusses the therapeutic targeting of different components of the KMT2 complexes.