Lysine methyltransferase 2 plays a key role in the encystation process in the parasite Giardia lamblia.

Histone post-translational modifications are extensively studied for their role in regulating gene transcription and cellular environmental adaptation. Research into these modifications has recently begun in the protozoan parasite Giardia lamblia, focusing on histone-modifying enzymes and specific post-translational changes. In the transformation from the trophozoite to the cyst form in the life cycle of this parasite, significant morphological and genetic alterations occur, culminating in the synthesis of cyst wall proteins responsible for forming the protective cyst wall. It has been previously demonstrated that histone deacetylation is required during encystation and that the enzyme lysine methyltransferase 1 is involved in the upregulation of encystation. Our study aims to extend the analysis to lysine methyltransferase 2 (GlKMT2) function. For this, two constructs were generated: one that downregulate the expression of GLKMT2 via antisense (glkmt2-as transgenic cells) and the other overexpressing GlKMT2 (glkmt2-ha transgenic cells). We found that the glktm2-as transgenic cells showed an arrest in progress at the late encystation stage. Consequently, the number of cysts produced was lower than that of the control cells. On the other hand, we found that the overexpression of GlKMT2 acts as a negative mutant of the enzyme. In this way, these glktm2-ha transgenic cells showed the same behavior during growth and encystation as glkmt2-as transgenic cells. This interplay between different enzymes acting during encystation reveals the complex process behind the differentiation of the parasite. Understanding how these enzymes play their role during the encystation of the parasite would allow the design of inhibitors to control the parasite.

Genetic Alterations of SMYD4 in Solid Tumors Using Integrative Multi-Platform Analysis.

SMYD4 is a member of the SMYD family that has lysine methyltransferase function. Little is known about the roles of SMYD4 in cancer. The aim of this study is to investigate genetic alterations in the SMYD4 gene across the most prevalent solid tumors and determine its potential as a biomarker. We performed an integrative multi-platform analysis of the most common mutations, copy number alterations (CNAs), and mRNA expression levels of the SMYD family genes using cohorts available at the Cancer Genome Atlas (TCGA), cBioPortal, and the Catalogue of Somatic Mutations in Cancer (COSMIC). SMYD genes displayed a lower frequency of mutations across the studied tumors, with none of the SMYD4 mutations detected demonstrating sufficient discriminatory power to serve as a biomarker. In terms of CNAs, SMYD4 consistently exhibited heterozygous loss and downregulation across all tumors evaluated. Moreover, SMYD4 showed low expression in tumor samples compared to normal samples, except for stomach adenocarcinoma. SMYD4 demonstrated a frequent negative correlation with other members of the SMYD family and a positive correlation between CNAs and mRNA expression. Additionally, patients with low SMYD4 expression in STAD and LUAD tumors exhibited significantly poorer overall survival. SMYD4 demonstrated its role as a tumor suppressor in the majority of tumors evaluated. The consistent downregulation of SMYD4, coupled with its association with cancer progression, underscores its potential usefulness as a biomarker.

[Phenotypic and genotypic spectrum of KMT2B dystonia. Description of three Colombian patients]. / Espectro fenotípico y genotípico de la distonía causada por el gen KMT2B. Descripción de tres casos colombianos.

INTRODUCTION: KMT2B-related dystonia is a childhood-onset movement disorder characterized by focal dystonia of the lower extremities progressing to generalized dystonia with predominant cervical, cranial, and laryngeal involvement. So far, fewer than 100 variants have been reported, the vast majority being de novo mutations. The presenting frame of KMT2B dystonia, with dysmorphology features and other complex neurologic symptoms shows the spectrum of KMT2B dystonia as a probable syndromic disease, rather than an isolated early-onset dystonia, which has been the classic view of the condition. CASE REPORTS: We report three patients who presented regression in their neurodevelopment, focal dystonia of the lower limbs with subsequent generalization, in whom two de novo variants were reported in the KMT2B gene, with a mean age of presentation lower than the average reported worldwide. CONCLUSIONS: We describe the largest local series of patients with KMT2B dystonia in Colombia (to our knowledge), which allows us to expand the genotype-phenotype relationship of this genetic dystonia. Although many affected individuals follow a similar disease course, it is important to determine clinical features that may be associated such as neurodevelopmental regression.

TITLE: Espectro fenotípico y genotípico de la distonía causada por el gen KMT2B. Descripción de tres casos colombianos.Introducción. La distonía relacionada con KMT2B es un trastorno del movimiento hipercinético, de inicio en la infancia, caracterizado inicialmente por distonía focal de las extremidades inferiores que progresa a una distonía generalizada con mayor afectación cervical, craneal y laríngea. Hasta el momento se han descrito aproximadamente 100 variantes causantes de enfermedad, y la mayoría son de novo. La presentación clínica de la distonía con hallazgos fenotípicos comunes en los pacientes, asociada a frecuente afectación del neurodesarrollo, afectación intelectual y otros trastornos del movimiento, hace pensar más en el espectro KMT2B como una condición sindrómica, más que en una distonía aislada de inicio temprano, como clásicamente se ha clasificado. Casos clínicos. Se presenta el caso de tres pacientes con regresión del neurodesarrollo, distonía focal de los miembros inferiores con posterior generalización, en quienes se identificaron tres variantes en el gen KMT2B, en dos de los casos de novo (en una de ellas se desconoce la segregación), y dos de ellas comunicadas por primera vez en la bibliografía. La edad media de presentación fue menor a la edad promedio notificada a nivel mundial. Conclusiones. Describimos una serie de pacientes colombianos con distonía DYT-KMT2B (la más grande en nuestro conocimiento a nivel local), lo que nos permite ampliar la relación genotipo-fenotipo de esta distonía genética. Si bien múltiples individuos afectados siguen un curso de enfermedad similar, es importante determinar las características clínicas que pueden estar asociadas, como la regresión del neurodesarrollo y su potencial clasificación como distonía compleja. Describimos, además, dos nuevas variantes asociadas al fenotipo.

NSD3 in Cancer: Unraveling Methyltransferase-Dependent and Isoform-Specific Functions.

NSD3 (nuclear receptor-binding SET domain protein 3) is a member of the NSD histone methyltransferase family of proteins. In recent years, it has been identified as a potential oncogene in certain types of cancer. The NSD3 gene encodes three isoforms, the long version (NSD3L), a short version (NSD3S) and the WHISTLE isoforms. Importantly, the NSD3S isoform corresponds to the N-terminal region of the full-length protein, lacking the methyltransferase domain. The chromosomal location of NSD3 is frequently amplified across cancer types, such as breast, lung, and colon, among others. Recently, this amplification has been correlated to a chromothripsis event, that could explain the different NSD3 alterations found in cancer. The fusion proteins containing NSD3 have also been reported in leukemia (NSD3-NUP98), and in NUT (nuclear protein of the testis) midline carcinoma (NSD3-NUT). Its role as an oncogene has been described by modulating different cancer pathways through its methyltransferase activity, or the short isoform of the protein, through protein interactions. Specifically, in this review we will focus on the functions that have been characterized as methyltransferase dependent, and those that have been correlated with the expression of the NSD3S isoform. There is evidence that both the NSD3L and NSD3S isoforms are relevant for cancer progression, establishing NSD3 as a therapeutic target. However, further functional studies are needed to differentiate NSD3 oncogenic activity as dependent or independent of the catalytic domain of the protein, as well as the contribution of each isoform and its clinical significance in cancer progression.

Histone Methyltransferase G9a Plays an Essential Role on Nicotine Preference in Zebrafish.

Psychostimulants regulate behavioral responses in zebrafish via epigenetic mechanisms. We have previously shown that DNA methylation and histone deacetylase (HDAC) inhibition abolish nicotine-induced conditioned place preference (CPP) but little is known about the role of histone methylation in addictive-like behaviors. To assess the influence of histone methylation on nicotine-CPP, zebrafish were treated with a histone (H3) lysine-9 (K9) dimethyltransferase G9a/GLP inhibitor, BIX-01294 (BIX), which was administered before conditioning sessions. We observed a dual effect of the inhibitor BIX: at high doses inhibited while at low doses potentiated nicotine reward. Transcriptional expression of α6 and α7 subunits of the nicotinic acetylcholine receptor and of G9a, DNA methyl transferase-3, and HDAC-1 was upregulated in zebrafish with positive scores for nicotine-CPP. Changes in relative levels of these mRNA molecules reflected the effects of BIX on nicotine reward. BIX treatment per sé did not affect transcriptional levels of epigenetic enzymes that regulate trimethylation or demethylation of H3. BIX reduced H3K9me2 protein levels in a dose-dependent manner in key structures of the reward pathway. Thus, our findings indicated that different doses of BIX differentially affect nicotine CPP via strong or weak inhibition of G9a/GLP activity. Additionally, we found that the lysine demethylase inhibitor daminozide abolished nicotine-CPP and drug seeking. Our data demonstrate that H3 methylation catalyzed by G9a/GLP is involved in nicotine-CPP induction. Dimethylation of K9 at H3 is an important epigenetic modification that should be considered as a potential therapeutic target to treat nicotine reward and perhaps other drug addictions.

Evidence of a synthetic lethality interaction between SETDB1 histone methyltransferase and CHD4 chromatin remodeling protein in a triple negative breast cancer cell line.

During the tumorigenic process, cancer cells may become overly dependent on the activity of backup cellular pathways for their survival, representing vulnerabilities that could be exploited as therapeutic targets. Certain molecular vulnerabilities manifest as a synthetic lethality relationship, and the identification and characterization of new synthetic lethal interactions may pave the way for the development of new therapeutic approaches for human cancer. Our goal was to investigate a possible synthetic lethal interaction between a member of the Chromodomain Helicase DNA binding proteins family (CHD4) and a member of the histone methyltransferases family (SETDB1) in the molecular context of a cell line (Hs578T) representing the triple negative breast cancer (TNBC), a subtype of breast cancer lacking validated molecular targets for treatment. Therefore, we employed the CRISPR-Cas9 gene editing tool to individually or simultaneously introduce indels in the genomic loci corresponding to the catalytic domains of SETDB1 and CHD4 in the Hs578T cell line. Our main findings included: a) introduction of indels in exon 22 of SETDB1 sensitized Hs578T to the action of the genotoxic chemotherapy doxorubicin; b) by sequentially introducing indels in exon 22 of SETDB1 and exon 23 of CHD4 and tracking the percentage of the remaining wild-type sequences in the mixed cell populations generated, we obtained evidence of the existence of a synthetic lethality interaction between these genes. Considering the lack of molecular targets in TNBC, our findings provided valuable insights for development of new therapeutic approaches not only for TNBC but also for other cancer types.

Histone Methyltransferases G9a/Ehmt2 and GLP/Ehmt1 Are Associated with Cell Viability and Poorer Prognosis in Neuroblastoma and Ewing Sarcoma.

Changes in epigenetic programming have been proposed as being key events in the initiation and progression of childhood cancers. HMT euchromatic histone lysine methyltransferase 2 (G9a, EHMT2), which is encoded by the G9a (Ehmt2) gene, as well as its related protein GLP, which is encoded by the GLP/Ehmt1 gene, participate in epigenetic regulation by contributing to a transcriptionally repressed chromatin state. G9a/GLP activation has been reported in several cancer types. Herein, we evaluated the role of G9a in two solid pediatric tumors: neuroblastoma (NB) and Ewing sarcoma (ES). Our results show that G9a/Ehmt2 and GLP/Ehmt1 expression is higher in tumors with poorer prognosis, including St4 International Neuroblastoma Staging System (INSS) stage, MYCN amplified NB, and metastatic ES. Importantly, higher G9a and GLP levels were associated with shorter patient overall survival (OS) in both NB and ES. Moreover, pharmacological inhibition of G9a/GLP reduced cell viability in NB and ES cells. These findings suggest that G9a and GLP are associated with more aggressive NB and ES tumors and should be further investigated as being epigenetic targets in pediatric solid cancers.

Child Neurology: KMT2B-Related Dystonia in a Young Child With Worsening Gait Abnormality.

KMT2B gene-related dystonia (DYT-KMT2B) is a primarily childhood-onset movement disorder that usually starts with lower limb dystonia progressing into generalized dystonia. Our patient described in this study experienced difficulty gaining weight, laryngomalacia, and feeding difficulties during infancy and later developed gait difficulties, frequent falls, and toe walking. Gait assessment revealed prominent bilateral intoeing, intermittent ankle inversion, and extension of left leg. At times, the gait seemed to be spastic. Whole-exome sequencing revealed a novel de novo heterozygous likely pathogenic variant, c.7913 T > A (p.V2638E), in the KMT2B gene located in chromosome 19. This variant, which has not been previously published as pathogenic or benign in the literature, can be added to the repertoire of KMT2B variants causing inherited dystonias.

NSD1 gene evolves under episodic selection within primates and mutations of specific exons in humans cause Sotos syndrome.

BACKGROUND: Modern human brains and skull shapes differ from other hominids. Brain growth disorders as micro- (ASPM, MCPH1) and macrocephaly (NFIX, GLI3) have been highlighted as relevant for the evolution in humans due to the impact in early brain development. Genes associated with macrocephaly have been reported to cause this change, for example NSD1 which causes Sotos syndrome. RESULTS: In this study we performed a systematic literature review, located the reported variants associated to Sotos syndrome along the gene domains, compared the sequences with close primates, calculated their similarity, Ka/Ks ratios, nucleotide diversity and selection, and analyzed the sequence and structural conservation with distant primates. We aimed to understand if NSD1 in humans differs from other primates since the evolution of NSD1 has not been analyzed in primates, nor if the localization of the mutations is limited to humans. Our study found that most variations causing Sotos syndrome are in exon 19, 22 and 10. In the primate comparison we did not detect Ka/Ks ratios > 1, but a high nucleotide diversity with non-synonymous variations in exons 10, 5, 9, 11 and 23, and sites under episodic selection in exon 5 and 23, and human, macaque/colobus/tarsier/galago and tarsier/lemur/colobus. Most of the domains are conserved in distant primates with a particular progressive development from a simple PWWP1 in O. garnetti to a complex structure in Human. CONCLUSION: NSD1 is a chromatin modifier that suggests that the selection could influence brain development during modern human evolution and is not present in other primates; however, nowadays the nucleotide diversity is associated with Sotos syndrome.

Early-onset generalized dystonia caused by a new mutation in the KMT2B gene: Case report / Nueva mutación en el gen KMT2B como causa de distonía generalizada de inicio temprano: reporte de caso.

Introduction: KMT2B-related dystonia is a recently described subtype of focal-onset dystonia in the lower limbs, evolving into a generalized form with cervical, oropharyngeal involvement, dysarthria, swallowing disorder and intellectual disability. Clinical case: We describe the case of a 10-year-old female patient, without a history of consanguinity or neurological disease. She manifested abnormal gait and dystonia with focal onset and progressive course with evolution into generalized dystonia, affecting orofacial and bulbar muscles, significant alteration of language and swallowing. Metabolic and systemic studies, including neuroimaging, were found to be normal. A complete genomic sequencing study was performed identifying a new, probably pathogenic, heterozygous variant in the KMT2B gene, c.1205delC, p. (Pro402Hisfs*5), causing displacement in the reading frame, a finding that explains the patient's phenotype and it is associated to autosomal dominant childhood-onset dystonia-28. Conclusion: We report a new heterozygous mutation in the KMT2B gene as a cause of generalized early-onset dystonia not reported in the literature until the date. The diagnosis of this pathology has implications for the treatment and prognosis of patients, given that therapeutic strategies implemented early can prevent the fast deterioration and severe course of this disease.

La distonía por mutación en el gen KMT2B es un subtipo recientemente descrito del inicio focal de la enfermedad en los miembros inferiores que, posteriormente, evoluciona a una forma generalizada con compromiso cervical y orofaríngeo, disartria, trastorno secundario de la deglución y discapacidad intelectual. Se describe el caso de una escolar de 10 años de edad, sin antecedentes de consanguinidad ni historia familiar de enfermedad neurológica, que presentó alteración de la marcha y distonía de inicio focal, de curso progresivo a una forma generalizada que afectó sus músculos orofaciales y bulbares con alteración significativa del lenguaje y la deglución. Los estudios metabólicos y sistémicos, incluidas las neuroimágenes, no evidenciaron anormalidades. Se hizo una secuenciación genómica completa y se identificó una nueva variante, probablemente patogénica heterocigota, en el gen KMT2B, la c.1205delC, p.(Pro402Hisfs*5), que causa desplazamiento en el marco de lectura. Este hallazgo explica el fenotipo de la paciente y la distonía de inicio temprano autosómica dominante. Se reporta una nueva mutación heterocigota del gen KMT2B como causa de distonía generalizada de inicio temprano, no reportada en la literatura especializada hasta el momento. El diagnóstico de esta afección tiene implicaciones en el tratamiento y el pronóstico de los pacientes, porque las estrategias terapéuticas tempranas pueden prevenir su rápido deterioro y un curso más grave de la enfermedad.

Unraveling the Role of the Tyrosine Tetrad from the Binding Site of the Epigenetic Writer MLL3 in the Catalytic Mechanism and Methylation Multiplicity.

MLL3, also known as KMT2C, is a lysine mono-methyltransferase in charge of the writing of an epigenetic mark on lysine 4 from histone 3. The catalytic site of MLL3 is composed of four tyrosines, namely, Y44, Y69, Y128, and Y130. Tyrosine residues are highly conserved among lysine methyltransferases' catalytic sites, although their complete function is still unclear. The exploration of how modifications on these residues from the enzymatic machinery impact the enzymatic activity of MLL3 could shed light transversally into the inner functioning of enzymes with similar characteristics. Through the use of QMMM calculations, we focus on the effect of the mutation of each tyrosine from the catalytic site on the enzymatic activity and the product specificity in the current study. While we found that the mutations of Y44 and Y128 by phenylalanine inactivated the enzyme, the mutation of Y128 by alanine reactivated the enzymatic activity of MLL3. Moreover, according to our models, the Y128A mutant was even found to be capable of di- and tri-methylate lysine 4 from histone 3, what would represent a gain of function mutation, and could be responsible for the development of diseases. Finally, we were able to establish the inactivation mechanism, which involved the use of Y130 as a water occlusion structure, whose conformation, once perturbed by its mutation or Y128 mutant, allows the access of water molecules that sequester the electron pair from lysine 4 avoiding its methylation process and, thus, increasing the barrier height.

Genetic investigation of syndromic forms of obesity.

BACKGROUND: Syndromic obesity (SO) refers to obesity with additional phenotypes, including intellectual disability (ID)/developmental delay (DD), dysmorphic features, or organ-specific abnormalities. SO is rare, has high phenotypic variability, and frequently follows a monogenic pattern of inheritance. However, the genetic etiology of most cases of SO has not been elucidated. SUBJECTS AND METHODS: In this study, we investigated 20 SO patients by whole-exome sequencing (WES) trios to identify causal genetic variants. RESULTS: 4/20 patients had negative results for array comparative genomic hybridization (aCGH) analyses. In the remaining 15 patients, in addition to SNVs and indels, CNVs were also evaluated. Pathogenic/likely pathogenic (P/LP) SNVs/indels were detected in 6/20 patients (involving MED13L, AHDC1, EHMT1, MYT1L, GRIA3, and SETD1A), while two patients carried an inherited VUS. In addition, P/LP CNVs were observed in 3/15 patients (involving SATG2, KIAA0442, and MEIS2). CONCLUSIONS: All nine detected P/LP variants involved genes already known to lead to syndromic ID/DD; however, for only two genes (EHMT1 and MYT1L) is the link with obesity well established. This is the first study applying a comprehensive genomic investigation of an SO cohort, showing a high diagnostic yield (~47%). Additionally, our findings suggested that several known ID/DD genes may also predispose individuals to SO.

G9a/EHMT2 is a Potential Prognostic Biomarker and Molecular Target in SHH Medulloblastoma.

Changes in epigenetic programming are associated with cancer development during childhood. Components of the epigenetic machinery involved in normal embryonic development and hijacked by pediatric cancers include enzymes mediating post-translational modifications of DNA and histones that regulate chromatin structure, such as histone methyltransferases (HMTs). Overexpression of the HMT G9a (euchromatic histone lysine methyltransferase 2, EHMT2) has been described in several cancer types. Medulloblastoma (MB), the main type of malignant brain tumor afflicting children, is currently classified into four molecular subgroups. Here, we show that expression level of the G9a/Ehmt2 gene is higher in MB tumors belonging to the SHH, Group 3, and Group 4 subgroups, compared to Wnt tumors. Remarkably, high G9a expression was significantly associated with shorter overall survival in MB patients. We also present evidence that G9a inhibition dose-dependently reduces MB cell viability. Our findings suggest that higher transcription of G9a may be a predictor of poor prognosis in patients with SHH MB, and that inhibiting G9a activity can display antitumor effects in MB.

EHMT2/G9a as an Epigenetic Target in Pediatric and Adult Brain Tumors.

Epigenetic mechanisms, including post-translational modifications of DNA and histones that influence chromatin structure, regulate gene expression during normal development and are also involved in carcinogenesis and cancer progression. The histone methyltransferase G9a (euchromatic histone lysine methyltransferase 2, EHMT2), which mostly mediates mono- and dimethylation by histone H3 lysine 9 (H3K9), influences gene expression involved in embryonic development and tissue differentiation. Overexpression of G9a has been observed in several cancer types, and different classes of G9a inhibitors have been developed as potential anticancer agents. Here, we review the emerging evidence suggesting the involvement of changes in G9a activity in brain tumors, namely glioblastoma (GBM), the main type of primary malignant brain cancer in adults, and medulloblastoma (MB), the most common type of malignant brain cancer in children. We also discuss the role of G9a in neuroblastoma (NB) and the drug development of G9a inhibitors.

Twenty-year follow-up of the facial phenotype of Brazilian patients with Sotos syndrome.

Sotos syndrome is characterized by overgrowth starting before birth through childhood with intellectual disability and craniofacial anomalies. The majority of patients are large for gestational age with developmental delay or intellectual disability. The majority of cases are caused by pathogenic variants in NSD1. The most consistent physical features in this disorder are facial dysmorphisms including prominent forehead, downslanted palpebral fissures, prognathism with a pointed chin, and a long and narrow face. We present a follow-up to a cohort of 11 individuals found to harbor heterozygous, pathogenic, or likely pathogenic variants in NSD1. We analyzed the facial dysmorphisms and the condition using retrospective over 20 years. Among these patients, followed in our medical genetics outpatient clinic for variable periods of time, all had a phenotype compatible with the characteristic Sotos syndrome facial features, which evolved with time and became superimposed with natural aging modifications. We present here a long-term follow-up of facial features of Brazilian patients with molecularly confirmed Sotos syndrome. In this largest Brazilian cohort of molecularly confirmed patients with Sotos syndrome to date, we provide a careful description of the facial phenotype, which becomes less pronounced with aging and possibly more difficult to recognize in adults. These results may have broad clinical implications for diagnosis and add to the global clinical delineation of this condition.

Does lineage plasticity enable escape from CAR-T cell therapy? Lessons from MLL-r leukemia.

The clinical success of engineered, CD19-directed chimeric antigen receptor (CAR) T cells in relapsed, refractory B-cell acute lymphoblastic leukemia (B-ALL) has generated great enthusiasm for the use of CAR T cells in patients with cytogenetics that portend a poor prognosis with conventional cytotoxic therapies. One such group includes infants and children with mixed lineage leukemia (MLL1, KMT2A) rearrangements (MLL-r), who fare much worse than patients with low- or standard-risk B-ALL. Although early clinical trials using CD19 CAR T cells for MLL-r B-ALL produced complete remission in most patients, relapse with CD19-negative disease was a common mechanism of treatment failure. Whereas CD19neg relapse has been observed across a broad spectrum of B-ALL patients treated with CD19-directed therapy, patients with MLL-r have manifested the emergence of AML, often clonally related to the B-ALL, suggesting that the inherent heterogeneity or lineage plasticity of MLL-r B-ALL may predispose patients to a myeloid relapse. Understanding the factors that enable and drive myeloid relapse may be important to devise strategies to improve durability of remissions. In this review, we summarize clinical observations to date with MLL-r B-ALL and generally discuss lineage plasticity as a mechanism of escape from immunotherapy.

DOT1L modulates the senescence-associated secretory phenotype through epigenetic regulation of IL1A.

Oncogene-induced senescence (OIS) is a stable cell cycle arrest that occurs in normal cells upon oncogene activation. Cells undergoing OIS express a wide variety of secreted factors that affect the senescent microenvironment termed the senescence-associated secretory phenotype (SASP), which is beneficial or detrimental in a context-dependent manner. OIS cells are also characterized by marked epigenetic changes. We globally assessed histone modifications of OIS cells and discovered an increase in the active histone marks H3K79me2/3. The H3K79 methyltransferase disruptor of telomeric silencing 1-like (DOT1L) was necessary and sufficient for increased H3K79me2/3 occupancy at the IL1A gene locus, but not other SASP genes, and was downstream of STING. Modulating DOT1L expression did not affect the cell cycle arrest. Together, our studies establish DOT1L as an epigenetic regulator of the SASP, whose expression is uncoupled from the senescence-associated cell cycle arrest, providing a potential strategy to inhibit the negative side effects of senescence while maintaining the beneficial inhibition of proliferation.

Epigenetic priming by EHMT1/EHMT2 in acute lymphoblastic leukemia induces TP53 and TP73 overexpression and promotes cell death.

Euchromatic histone-lysine N-methyltransferase 1 (EHMT1) and EHMT2 are upregulated in various human cancers, and their deregulation is associated with tumor development and progression. In this paper, we investigated the expression level of EHMT1/EHMT2 in acute lymphoblastic leukemia (ALL) and whether the modulation of these enzymes could have any cellular or molecular impact on ALL cells. For this, we used UNC0646 as a priming strategy to target EHMT1/EHMT2 and investigated its effect on proliferation and cell viability of Jurkat cells by MTT assay. Then, considering the IC50 and IC75, cellular death was determined by Annexin V/PI staining using flow cytometry. Finally, we investigated by RT-PCR the molecular bases that could be involved in the observed effects. Interestingly, accessing the International Microarray Innovations in Leukemia (MILE) study group, we detected that both EHMT1 and EHMT2 are overexpressed in ALL. More important, we determined that inhibition of EHMT1/EHMT2 significantly decreased Jurkat cell viability in a dose-dependent manner. Accordingly, we observed that inhibition of EHMT1/EHMT2 promoted Jurkat cell death, which was accompanied by increased expression of P53, TP73, BAX, and MDM4. These results clearly indicate that inhibition of EHMT1/EHMT2 induces pro-apoptotic gene expression in ALL and promotes cell death. More importantly, the modulation of these histone methyltransferases may be a promising epigenetic target for ALL treatment.

Catalytic inhibition of H3K9me2 writers disturbs epigenetic marks during bovine nuclear reprogramming.

Orchestrated events, including extensive changes in epigenetic marks, allow a somatic nucleus to become totipotent after transfer into an oocyte, a process termed nuclear reprogramming. Recently, several strategies have been applied in order to improve reprogramming efficiency, mainly focused on removing repressive epigenetic marks such as histone methylation from the somatic nucleus. Herein we used the specific and non-toxic chemical probe UNC0638 to inhibit the catalytic activity of the histone methyltransferases EHMT1 and EHMT2. Either the donor cell (before reconstruction) or the early embryo was exposed to the probe to assess its effect on developmental rates and epigenetic marks. First, we showed that the treatment of bovine fibroblasts with UNC0638 did mitigate the levels of H3K9me2. Moreover, H3K9me2 levels were decreased in cloned embryos regardless of treating either donor cells or early embryos with UNC0638. Additional epigenetic marks such as H3K9me3, 5mC, and 5hmC were also affected by the UNC0638 treatment. Therefore, the use of UNC0638 did diminish the levels of H3K9me2 and H3K9me3 in SCNT-derived blastocysts, but this was unable to improve their preimplantation development. These results indicate that the specific reduction of H3K9me2 by inhibiting EHMT1/2 during nuclear reprogramming impacts the levels of H3K9me3, 5mC, and 5hmC in preimplantation bovine embryos.

Epigenetic regulation of protein translation in KMT2A-rearranged AML.

Inhibition of the H3K79 histone methyltransferase DOT1L has exhibited encouraging preclinical and early clinical activity in KMT2A (MLL)-rearranged leukemia, supporting the development of combinatorial therapies. Here, we investigated two novel combinations: dual inhibition of the histone methyltransferases DOT1L and EZH2, and the combination with a protein synthesis inhibitor. EZH2 is the catalytic subunit in the polycomb repressive complex 2 (PRC2), and inhibition of EZH2 has been reported to have preclinical activity in KMT2A-r leukemia. When combined with DOT1L inhibition, however, we observed both synergistic and antagonistic effects. Interestingly, antagonistic effects were not due to PRC2-mediated de-repression of HOXA9. HOXA cluster genes are key canonical targets of both KMT2A and the PRC2 complex. The independence of the HOXA cluster from PRC2 repression in KMT2A-r leukemia thus affords important insights into leukemia biology. Further studies revealed that EZH2 inhibition counteracted the effect of DOT1L inhibition on ribosomal gene expression. We thus identified a previously unrecognized role of DOT1L in regulating protein production. Decreased translation was one of the earliest effects measurable after DOT1L inhibition and specific to KMT2A-rearranged cell lines. H3K79me2 chromatin immunoprecipitation sequencing patterns over ribosomal genes were similar to those of the canonical KMT2A-fusion target genes in primary AML patient samples. The effects of DOT1L inhibition on ribosomal gene expression prompted us to evaluate the combination of EPZ5676 with a protein translation inhibitor. EPZ5676 was synergistic with the protein translation inhibitor homoharringtonine (omacetaxine), supporting further preclinical/clinical development of this combination. In summary, we discovered a novel epigenetic regulation of a metabolic process-protein synthesis-that plays a role in leukemogenesis and affords a combinatorial therapeutic opportunity.