Protein methyltransferase 7 deficiency in Leishmania major increases neutrophil associated pathology in murine model.

Leishmania major is the main causative agent of cutaneous leishmaniasis in the Old World. In Leishmania parasites, the lack of transcriptional control is mostly compensated by post-transcriptional mechanisms. Methylation of arginine is a conserved post-translational modification executed by Protein Arginine Methyltransferase (PRMTs). The genome from L. major encodes five PRMT homologs, including the cytosolic protein associated with several RNA-binding proteins, LmjPRMT7. It has been previously reported that LmjPRMT7 could impact parasite infectivity. In addition, a more recent work has clearly shown the importance of LmjPRMT7 in RNA-binding capacity and protein stability of methylation targets, demonstrating the role of this enzyme as an important epigenetic regulator of mRNA metabolism. In this study, we unveil the impact of PRMT7-mediated methylation on parasite development and virulence. Our data reveals that higher levels of LmjPRMT7 can impair parasite pathogenicity, and that deletion of this enzyme rescues the pathogenic phenotype of an attenuated strain of L. major. Interestingly, lesion formation caused by LmjPRMT7 knockout parasites is associated with an exacerbated inflammatory reaction in the tissue correlated with an excessive neutrophil recruitment. Moreover, the absence of LmjPRMT7 also impairs parasite development within the sand fly vector Phlebotomus duboscqi. Finally, a transcriptome analysis shed light onto possible genes affected by depletion of this enzyme. Taken together, this study highlights how post-transcriptional regulation can affect different aspects of the parasite biology.

Knockdown of SETDB1 inhibits breast cancer progression by miR-381-3p-related regulation.

BACKGROUND: SET domain bifurcated 1 (SETDB1) has been widely considered as an oncogene playing a critical role in many human cancers, including breast cancer. Nevertheless, the molecular mechanism by which SETDB1 regulates breast cancer tumorigenesis is still unknown. METHODS: qRT-PCR assay or western blot analysis was performed to assess the expression level of SETDB1 mRNA or protein, respectively. siSETDB1, pCMV6-XL5-SETDB1, miR-381-3p mimic, or miR-381-3p inhibitor was transfected into cells to regulate the expression of SETDB1 or miR-381-3p. MiRNA directly interacted with SETDB1 was verified by luciferase reporter assay and RNA immunoprecipitation. CCK-8 assay, colony formation assay, flow cytometric analysis, and transwell assay were used to detect the abilities of cell proliferation, cell cycle progression and migration, respectively. Animal model of xenograft tumor was used to observe the regulatory effect of SETDB1 on tumor growth in vivo. RESULTS: We verified that SETDB1 mRNA level was upregulated in breast cancer tissues and cell lines, and SETDB1 depletion led to a suppression of cell proliferation, cell cycle progression and migration in vitro, as well as tumor growth in vivo. SETDB1 was verified to be a target of miR-381-3p. Moreover, miR-381-3p overexpression suppressed cell proliferation, cell cycle progression and migration, whereas SETDB1 abated miR-381-3p-mediated regulatory function on breast cancer cells. CONCLUSIONS: This study revealed that SETDB1 knockdown might suppress breast cancer progression at least partly by miR-381-3p-related regulation, providing a novel prospect in breast cancer therapy.

Knockdown of SETDB1 inhibits breast cancer progression by miR-381-3p-related regulation

BACKGROUND: SET domain bifurcated 1 (SETDB1) has been widely considered as an oncogene playing a critical role in many human cancers, including breast cancer. Nevertheless, the molecular mechanism by which SETDB1 regulates breast cancer tumorigenesis is still unknown. METHODS: qRT-PCR assay or western blot analysis was performed to assess the expression level of SETDB1 mRNA or protein, respectively. siSETDB1, pCMV6-XL5-SETDB1, miR-381-3p mimic, or miR-381-3p inhibitor was transfected into cells to regulate the expression of SETDB1 or miR-381-3p. MiRNA directly interacted with SETDB1 was verified by luciferase reporter assay and RNA immunoprecipitation. CCK-8 assay, colony formation assay, flow cytometric analysis, and transwell assay were used to detect the abilities of cell proliferation, cell cycle progression and migration, respectively. Animal model of xenograft tumor was used to observe the regulatory effect of SETDB1 on tumor growth in vivo. RESULTS: We verified that SETDB1 mRNA level was upregulated in breast cancer tissues and cell lines, and SETDB1 depletion led to a suppression of cell proliferation, cell cycle progression and migration in vitro, as well as tumor growth in vivo. SETDB1 was verified to be a target of miR-381-3p. Moreover, miR-381-3p overexpression suppressed cell proliferation, cell cycle progression and migration, whereas SETDB1 abated miR-381-3p-mediated regulatory function on breast cancer cells. CONCLUSIONS: This study revealed that SETDB1 knockdown might suppress breast cancer progression at least partly by miR-381-3p-related regulation, providing a novel prospect in breast cancer therapy.

Prognostic value of ERCC1, RRM1, BRCA1 and SETDB1 in early stage of non-small cell lung cancer.

INTRODUCTION: Nowadays, 40 % of early-stage NSCLC patients relapse in the 2 years following resection, suggesting a mis-staging in this group of patients who are not receiving adjuvant chemotherapy. Although different biomarkers, such as ERCC1, RRM1 and BRCA1 have been found to present prognostic value in advanced NSCLC patients, in early-stage NSCLC patients its relevance remains unclear. Moreover, SETDB1 has been recently proposed as a bona fide oncogene in lung tumourigenesis and related with metastasis. The aim of the present study was to analyze the prognostic value of ERCC1, RRM1, BRCA1 and SETDB1 expression levels in NSCLC patients at stage I. PATIENTS AND METHODS: ERCC1, RRM1, BRCA1 and SETDB1 expression at mRNA level was analyzed by real-time quantitative RT-PCR in fresh-frozen tumor and normal adjacent lung tissue samples from 64 stage I NSCLC patients. Later, significant association between gene expression levels, clinicopathological characteristics and patient's disease-free survival was assessed. RESULTS: We did not find any statistically significant correlation between gene expression and gender, age, histological type or smoking status. Univariate followed by multivariate Cox analysis showed that higher levels of BRCA1 and SETDB1 expression were significantly associated with shorter disease-free survival in stage I NSCLC patients. CONCLUSION: Our study finds that ERCC1 and RRM1 are not independent prognostic factors of recurrence in stage I NSCLC patients. By contrast, BRCA1 and SETDB1 stand out as the most significant prognostic markers in this group of patients, appearing as promising tools to predict tumor recurrence in early-stage NSCLC patients.

Methylation of histone H3 lysine 9 occurs during translation.

Histone post-translational modifications are key contributors to chromatin structure and function, and participate in the maintenance of genome stability. Understanding the establishment and maintenance of these marks, along with their misregulation in pathologies is thus a major focus in the field. While we have learned a great deal about the enzymes regulating histone modifications on nucleosomal histones, much less is known about the mechanisms establishing modifications on soluble newly synthesized histones. This includes methylation of lysine 9 on histone H3 (H3K9), a mark that primes the formation of heterochromatin, a critical chromatin landmark for genome stability. Here, we report that H3K9 mono- and dimethylation is imposed during translation by the methyltransferase SetDB1. We discuss the importance of these results in the context of heterochromatin establishment and maintenance and new therapeutic opportunities in pathologies where heterochromatin is perturbed.

Alternative splicing at the right time.

Alternative splicing (AS) allows the production of multiple mRNA variants from a single gene, which contributes to increase the complexity of the proteome. There is evidence that AS is regulated not only by auxiliary splicing factors, but also by components of the core spliceosomal machinery, as well as through epigenetic modifications. However, to what extent these different mechanisms contribute to the regulation of AS in response to endogenous or environmental stimuli is still unclear. Circadian clocks allow organisms to adjust physiological processes to daily changes in environmental conditions. Here we review recent evidence linking circadian clock and AS, and discuss the role of Protein Arginine Methyltransferase 5 (PRMT5) in these processes. We propose that the interactions between daily oscillations in AS and circadian rhythms in the expression of splicing factors and epigenetic regulators offer a great opportunity to dissect the contribution of these mechanisms to the regulation of AS in a physiologically relevant context.

A methyl transferase links the circadian clock to the regulation of alternative splicing.

Circadian rhythms allow organisms to time biological processes to the most appropriate phases of the day-night cycle. Post-transcriptional regulation is emerging as an important component of circadian networks, but the molecular mechanisms linking the circadian clock to the control of RNA processing are largely unknown. Here we show that PROTEIN ARGININE METHYL TRANSFERASE 5 (PRMT5), which transfers methyl groups to arginine residues present in histones and Sm spliceosomal proteins, links the circadian clock to the control of alternative splicing in plants. Mutations in PRMT5 impair several circadian rhythms in Arabidopsis thaliana and this phenotype is caused, at least in part, by a strong alteration in alternative splicing of the core-clock gene PSEUDO RESPONSE REGULATOR 9 (PRR9). Furthermore, genome-wide studies show that PRMT5 contributes to the regulation of many pre-messenger-RNA splicing events, probably by modulating 5'-splice-site recognition. PRMT5 expression shows daily and circadian oscillations, and this contributes to the mediation of the circadian regulation of expression and alternative splicing of a subset of genes. Circadian rhythms in locomotor activity are also disrupted in dart5-1, a mutant affected in the Drosophila melanogaster PRMT5 homologue, and this is associated with alterations in splicing of the core-clock gene period and several clock-associated genes. Our results demonstrate a key role for PRMT5 in the regulation of alternative splicing and indicate that the interplay between the circadian clock and the regulation of alternative splicing by PRMT5 constitutes a common mechanism that helps organisms to synchronize physiological processes with daily changes in environmental conditions.

The HP1alpha-CAF1-SetDB1-containing complex provides H3K9me1 for Suv39-mediated K9me3 in pericentric heterochromatin.

Trimethylation of lysine 9 in histone H3 (H3K9me3) enrichment is a characteristic of pericentric heterochromatin. The hypothesis of a stepwise mechanism to establish and maintain this mark during DNA replication suggests that newly synthesized histone H3 goes through an intermediate methylation state to become a substrate for the histone methyltransferase Suppressor of variegation 39 (Suv39H1/H2). How this intermediate methylation state is achieved and how it is targeted to the correct place at the right time is not yet known. Here, we show that the histone H3K9 methyltransferase SetDB1 associates with the specific heterochromatin protein 1alpha (HP1alpha)-chromatin assembly factor 1 (CAF1) chaperone complex. This complex monomethylates K9 on non-nucleosomal histone H3. Therefore, the heterochromatic HP1alpha-CAF1-SetDB1 complex probably provides H3K9me1 for subsequent trimethylation by Suv39H1/H2 in pericentric regions. The connection of CAF1 with DNA replication, HP1alpha with heterochromatin formation and SetDB1 for H3K9me1 suggests a highly coordinated mechanism to ensure the propagation of H3K9me3 in pericentric heterochromatin during DNA replication.

Correlation of sinefungin susceptibility and drug-affinity for protein carboxymethyltransferase activity in American Leishmania species.

Among promastigotes of 22 different American Leishmania strains, a 5000-fold variation in sinefungin susceptibility was found, apparently independent of their taxonomic classification, although L. mexicana strains did tend to be more resistant than L. braziliensis. Protein carboxymethyltransferase (EC 2.1.1.24) and glycine N-methyltransferase (EC 2.1.1.20) activities were not substantially different in sinefungin-susceptible and -resistant American Leishmania strains. However, when [methyl-3H]methionine incorporation into total protein or gamma-glutamyl residues of leishmanial proteins was carried out in the presence or absence of sinefungin, protein carboxymethylating activity was significantly inhibited only in sinefungin-susceptible Leishmania strains. Furthermore, when protein carboxymethyltransferase activity was purified from several leishmanial strains to a state of electrophoretic homogeneity (sp. act. = 240 nmol h-1 (mg protein)-1), the enzyme from the resistant cells showed a higher inhibition constant (mean Ki 55 microM against 2 microM in susceptible cells) for sinefungin. This 28-times stronger affinity of the susceptible cell enzyme towards sinefungin despite normal protein carboxymethyltransferase specific activity seems to be a key element of the resistance mechanism of certain American Leishmania strains.