S-adenosylmethionine Biosynthesis Research Articles

Abstract C053: Autophagy regulates MAT2A in response to hypoxia in pancreatic cancer cells

Abstract Methionine adenosyltransferase 2A (MAT2A) is an essential enzyme responsible for biosynthesis of S-adenosylmethionine, a methyl-group donor of various methyltransferases. Pancreatic ductal adenocarcinoma PDAC is characterized by severe hypoxia and upregulates autophagy and lysosomal biogenesis to enhance nutrient recycling and stress resistance. Here we show that a subset of MAT2A is targeted via the autophagy pathway for degradation by the lysosome under normoxia in PDAC cells, but is subsequently protected against degradation under hypoxia. Mechanistically, we show that the autophagy cargo receptor SQSTM1 (p62) binds to MAT2A in a ubiquitin-dependent manner under normoxia to regulate its autophagic capture. Under hypoxic conditions, stabilized MAT2A potentially facilities increased flux of methionine towards increased SAM, suggesting that protection of MAT2A against lysosomal degradation might enable alterations in methionine metabolism that drive epigenetic and metabolic adaptation to stress. Citation Format: Yang Yang, Wenping Wang, Gilles Rademaker, Mirunalini Ravichandran, Jingjie Hu, Alexander Li, Joseph D. Mancias, Jessie Yanxiang Guo, Rushika M. Perera. Autophagy regulates MAT2A in response to hypoxia in pancreatic cancer cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C053.

S-adenosylmethionine biosynthesis is a targetable metabolic vulnerability in multiple myeloma.

Multiple myeloma (MM) is the second most prevalent hematologic malignancy and is incurable because of the inevitable development of drug resistance. Methionine adenosyltransferase 2α (MAT2A) is the primary producer of the methyl donor S-adenosylmethionine (SAM) and several studies have documented MAT2A deregulation in different solid cancers. As the role of MAT2A in MM has not been investigated yet, the aim of this study was to clarify the potential role and underlying molecular mechanisms of MAT2A in MM, exploring new therapeutic options to overcome drug resistance. By analyzing publicly available gene expression profiling data, MAT2A was found to be more highly expressed in patient-derived myeloma cells than in normal bone marrow plasma cells. The expression of MAT2A correlated with an unfavorable prognosis in relapsed patients. MAT2A inhibition in MM cells led to a reduction in intracellular SAM levels, which resulted in impaired cell viability and proliferation, and induction of apoptosis. Further mechanistic investigation demonstrated that MAT2A inhibition inactivated the mTOR-4EBP1 pathway, accompanied by a decrease in protein synthesis. MAT2A targeting in vivo with the small molecule compound FIDAS-5 was able to significantly reduce tumor burden in the 5TGM1 model. Finally, we found that MAT2A inhibition can synergistically enhance the anti-MM effect of the standard-of-care agent bortezomib on both MM cell lines and primary human CD138+ MM cells. In summary, we demonstrate that MAT2A inhibition reduces MM cell proliferation and survival by inhibiting mTOR-mediated protein synthesis. Moreover, our findings suggest that the MAT2A inhibitor FIDAS-5 could be a novel compound to improve bortezomib-based treatment of MM.

Sumoylation of methionine adenosyltransferase alpha 1 promotes mitochondrial dysfunction in alcohol-associated liver disease.

Methionine adenosyltransferase alpha1 (MATα1) is responsible for the biosynthesis of S-adenosylmethionine in normal liver. Alcohol consumption enhances MATα1 interaction with peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1), which blocks MATα1 mitochondrial targeting, resulting in lower mitochondrial MATα1 content and mitochondrial dysfunction in alcohol-associated liver disease (ALD) in part through upregulation of cytochrome P450 2E1. Conversely, alcohol intake enhances SUMOylation, which enhances cytochrome P450 2E1 expression. MATα1 has potential SUMOylation sites, but whether MATα1 is regulated by SUMOylation in ALD is unknown. Here, we investigated if MATα1 is regulated by SUMOylation and, if so, how it impacts mitochondrial function in ALD. Proteomics profiling revealed hyper-SUMOylation of MATα1, and prediction software identified lysine 48 (K48) as the potential SUMOylation site in mice (K47 in humans). Experiments with primary hepatocytes, mouse, and human livers revealed that SUMOylation of MAT1α by SUMO2 depleted mitochondrial MATα1. Furthermore, mutation of MATα1 K48 prevented ethanol-induced mitochondrial membrane depolarization, MATα1 depletion, and triglyceride accumulation. Additionally, CRISPR/CRISPR associated protein 9 gene editing of MATα1 at K48 hindered ethanol-induced MATα1-PIN1 interaction, degradation, and phosphorylation of MATα1 in vitro. In vivo, CRISPR/CRISPR associated protein 9 MATα1 K48 gene-edited mice were protected from ethanol-induced fat accumulation, liver injury, MATα1-PIN1 interaction, mitochondrial MATα1 depletion, mitochondrial dysfunction, and low S-adenosylmethionine levels. Taken together, our findings demonstrate an essential role for SUMOylation of MATα1 K48 for interaction with PIN1 in ALD. Preventing MATα1 K48 SUMOylation may represent a potential treatment strategy for ALD.

Positive Regulation of S-Adenosylmethionine on Chondrocytic Differentiation via Stimulation of Polyamine Production and the Gene Expression of Chondrogenic Differentiation Factors.

S-adenosylmethionine (SAM) is considered to be a useful therapeutic agent for degenerative cartilage diseases, although its mechanism is not clear. We previously found that polyamines stimulate the expression of differentiated phenotype of chondrocytes. We also found that the cellular communication network factor 2 (CCN2) played a huge role in the proliferation and differentiation of chondrocytes. Therefore, we hypothesized that polyamines and CCN2 could be involved in the chondroprotective action of SAM. In this study, we initially found that exogenous SAM enhanced proteoglycan production but not cell proliferation in human chondrocyte-like cell line-2/8 (HCS-2/8) cells. Moreover, SAM enhanced gene expression of cartilage-specific matrix (aggrecan and type II collagen), Sry-Box transcription factor 9 (SOX9), CCN2, and chondroitin sulfate biosynthetic enzymes. The blockade of the methionine adenosyltransferase 2A (MAT2A) enzyme catalyzing intracellular SAM biosynthesis restrained the effect of SAM on chondrocytes. The polyamine level in chondrocytes was higher in SAM-treated culture than control culture. Additionally, Alcian blue staining and RT-qPCR indicated that the effects of SAM on the production and gene expression of aggrecan were reduced by the inhibition of polyamine synthesis. These results suggest that the stimulation of polyamine synthesis and gene expression of chondrogenic differentiation factors, such as CCN2, account for the mechanism underlying the action of SAM on chondrocytes.

Formaldehyde regulates S-adenosylmethionine biosynthesis and one-carbon metabolism.

One-carbon metabolism is an essential branch of cellular metabolism that intersects with epigenetic regulation. In this work, we show how formaldehyde (FA), a one-carbon unit derived from both endogenous sources and environmental exposure, regulates one-carbon metabolism by inhibiting the biosynthesis of S-adenosylmethionine (SAM), the major methyl donor in cells. FA reacts with privileged, hyperreactive cysteine sites in the proteome, including Cys120 in S-adenosylmethionine synthase isoform type-1 (MAT1A). FA exposure inhibited MAT1A activity and decreased SAM production with MAT-isoform specificity. A genetic mouse model of chronic FA overload showed a decrease n SAM and in methylation on selected histones and genes. Epigenetic and transcriptional regulation of Mat1a and related genes function as compensatory mechanisms for FA-dependent SAM depletion, revealing a biochemical feedback cycle between FA and SAM one-carbon units.

CGMP functions as an important messenger involved in SlSAMS1-regulated salt stress tolerance in tomato

Salt stress adversely affects the growth, development, and yield of tomato (Solanum lycopersicum). SAM Synthetase (SAMS), which is responsible for the biosynthesis of S-adenosylmethionine (SAM, a precursor of polyamine biosynthesis), participates in plant response to abiotic stress. However, the regulatory mechanism of SAMS-mediated salt stress tolerance remains elusive. In this study, we characterized a SAMS homologue SlSAMS1 in tomato. We found that SlSAMS1 is highly expressed in tomato roots, and its expression can be induced by salt stress. Crucially, overexpression of SlSAMS1 in tomato enhances salt stress tolerance. Through metabolomic profiling, we identified some differentially accumulated metabolites, especially, a secondary messenger guanosine 3′,5′-cyclic monophosphate (cGMP) which may play a key role in SlSAMS1-regulated salt tolerance. A series of physiological and biochemical data suggest that cGMP alleviates salt stress-induced growth inhibition, and potentially acts downstream of the polyamine-nitric oxide (PA-NO) signaling pathway to trigger H2O2 signaling in response to salt stress. Taken together, the study reveals that SlSAMS1 regulates tomato salt tolerance via the PA–NO–cGMP-H2O2 signal module. Our findings elucidate the regulatory pathway of SlSAMS1-induced plant response to salt stress and indicate a pivotal role of cGMP in salt tolerance.

Flaxseed Reduces Cancer Risk by Altering Bioenergetic Pathways in Liver: Connecting SAM Biosynthesis to Cellular Energy.

This article illustrates how dietary flaxseed can be used to reduce cancer risk, specifically by attenuating obesity, type 2 diabetes, and non-alcoholic fatty liver disease (NAFLD). We utilize a targeted metabolomics dataset in combination with a reanalysis of past work to investigate the "metabo-bioenergetic" adaptations that occur in White Leghorn laying hens while consuming dietary flaxseed. Recently, we revealed how the anti-vitamin B6 effects of flaxseed augment one-carbon metabolism in a manner that accelerates S-adenosylmethionine (SAM) biosynthesis. Researchers recently showed that accelerated SAM biosynthesis activates the cell's master energy sensor, AMP-activated protein kinase (AMPK). Our paper provides evidence that flaxseed upregulates mitochondrial fatty acid oxidation and glycolysis in liver, concomitant with the attenuation of lipogenesis and polyamine biosynthesis. Defatted flaxseed likely functions as a metformin homologue by upregulating hepatic glucose uptake and pyruvate flux through the pyruvate dehydrogenase complex (PDC) in laying hens. In contrast, whole flaxseed appears to attenuate liver steatosis and body mass by modifying mitochondrial fatty acid oxidation and lipogenesis. Several acylcarnitine moieties indicate Randle cycle adaptations that protect mitochondria from metabolic overload when hens consume flaxseed. We also discuss a paradoxical finding whereby flaxseed induces the highest glycated hemoglobin percentage (HbA1c%) ever recorded in birds, and we suspect that hyperglycemia is not the cause. In conclusion, flaxseed modifies bioenergetic pathways to attenuate the risk of obesity, type 2 diabetes, and NAFLD, possibly downstream of SAM biosynthesis. These findings, if reproducible in humans, can be used to lower cancer risk within the general population.

Genetically encoded RNA-based sensors with Pepper fluorogenic aptamer.

Sensors to measure the abundance and signaling of intracellular molecules are crucial for understanding their physiological functions. Although conventional fluorescent protein-based sensors have been designed, RNA-based sensors are promising imaging tools. Numerous RNA-based sensors have been developed. These sensors typically contain RNA G-quadruplex (RG4) motifs and thus may be suboptimal in living cells. Here we describe RNA-based sensors based on Pepper, a fluorogenic RNA without an RG4 motif. With Pepper, we engineered various sensors for metabolites, synthetic compounds, proteins and metal ions in vitro and in living cells. In addition, these sensors show high activation and selectivity, demonstrating their universality and robustness. In the case of sensors responding to S-adenosylmethionine (SAM), a metabolite produced by methionine adenosyltransferase (MATase), we showed that our sensors exhibited positively correlated fluorescence responding to different SAM levels. Importantly, we revealed the SAM biosynthesis pathway and monitored MATase activity and gene expression spatiotemporally in living individual human cells. Additionally, we constructed a ratiometric SAM sensor to determine the inhibition efficacy of a MATase inhibitor in living cells. Together, these sensors comprising Pepper provide a useful platform for imaging diverse cellular targets and their signaling pathway.

Gluconeogenic enzyme PCK1 supports S-adenosylmethionine biosynthesis and promotes H3K9me3 modification to suppress hepatocellular carcinoma progression.

Deciphering the crosstalk between metabolic reprogramming and epigenetic regulation is a promising strategy for cancer therapy. In this study, we discovered that the gluconeogenic enzyme PCK1 fueled the generation of S-adenosylmethionine (SAM) through the serine synthesis pathway. The methyltransferase SUV39H1 catalyzed SAM, which served as a methyl donor to support H3K9me3 modification, leading to the suppression of the oncogene S100A11. Mechanistically, PCK1 deficiency-induced oncogenic activation of S100A11 was due to its interaction with AKT1, which upregulated PI3K/AKT signaling. Intriguingly, the progression of hepatocellular carcinoma (HCC) driven by PCK1 deficiency was suppressed by SAM supplement or S100A11 KO in vivo and in vitro. These findings reveal the availability of the key metabolite SAM as a bridge connecting the gluconeogenic enzyme PCK1 and H3K9 trimethylation in attenuating HCC progression, thus suggesting a potential therapeutic strategy against HCC.

AtSAMS regulates floral organ development by DNA methylation and ethylene signaling pathway

S-adenosylmethionine synthase is the key enzyme involved in the biosynthesis of S-adenosylmethionine, which serves as the universal methyl group donor and a common precursor for the biosynthesis of ethylene and polyamines. However, little is known about how SAMS controls plant development. Here, we report that the abnormal floral organ development in the AtSAMS-overexpressing plants is caused by DNA demethylation and ethylene signaling. The whole-genome DNA methylation level decreased, and ethylene content increased in SAMOE. Wild-type plants treated with DNA methylation inhibitor mimicked the phenotypes and the ethylene levels in SAMOE, suggesting that DNA demethylation enhanced ethylene biosynthesis, which led to abnormal floral organ development. DNA demethylation and elevated ethylene resulted in changes in the expression of ABCE genes, which is essential for floral organ development. Furthermore, the transcript levels of ACE genes were highly correlated to their methylation levels, except for the down-regulation of the B gene, which might have resulted from demethylation-independent ethylene signaling. SAMS-mediated methylation and ethylene signaling might create crosstalk in the process of floral organ development. Together, we provide evidence that AtSAMS regulates floral organ development by DNA methylation and ethylene signaling pathway.

Utilization of high-K+-cane molasses for enhanced S-Adenosylmethionine production by manipulation of a K+ transport channel in Saccharomyces cerevisiae

S-Adenosylmethionine (SAM) is a valuable compound extensively used in depression treatment and biological methyl donor, which is biosynthesized from ATP and L-methionine with SAM synthase (SAM-s) as a catalyst. In this research, the weak SAM-s activity was a key factor and led to low SAM titer in Saccharomyces cerevisiae. Then, a novel K+ uptake channel was introduced to the SAM production pathway of Saccharomyces cerevisiae, activated by K+ in molasses to enhance the SAM synthase (SAM-s) activity and thereby improve the production efficiency of SAM. As a result, the intracellular K+ concentration and SAM-s activity were 1.23- and 1.31-fold higher than the control leading to a 24 % increase to 0.93 ± 0.04 g/L in SAM titer. In combination with bioprocess optimization resulted in a final yield of 2.22 ± 0.01 g/L in shake flasks and 15.37 ± 0.89 g/L in a 5-L bioreactor from pretreated molasses. This work provides a practical and cost-effective strategy for the large-scale biosynthesis of SAM from cane molasses.

Development of a synthetic transcription factor-based S-adenosylmethionine biosensor in Saccharomyces cerevisiae.

S-Adenosylmethionine (SAM) is a crucial small-molecule metabolite widely used in food and medicine. The development of high-throughput biosensors for SAM biosynthesis can significantly improve the titer of SAM. This paper constructed a synthetic transcription factor (TF)-based biosensor for SAM detecting in Saccharomyces cerevisiae. The synthetic TF, named MetJ-hER-VP16, consists of an Escherichia coli-derived DNA-binding domain MetJ, GS linker, the human estrogen receptor binding domain hER, and the viral activation domain VP16. The synthetic biosensor is capable of sensing SAM in a dose-dependent manner with fluorescence as the output. Additionally, it is tightly regulated by the inducer SAM and β-estradiol, which means that the fluorescence output is only available when both are present together. The synthetic SAM biosensor could potentially be applied for high-throughput metabolic engineering and is expected to improve SAM production.

Untargeted Metabolomics Combined with Metabolic Flux Analysis Reveals the Mechanism of Sodium Citrate for High S-Adenosyl-Methionine Production by Pichia pastoris

S-adenosyl-methionine (SAM) is crucial for organisms to maintain some physiological functions. However, the inconsistency between high L-methionine feeding rate and yield during SAM production at an industrial scale and its metabolic mechanism have not been elucidated. Here, the cellular metabolic mechanism of feeding sodium citrate to the Pichia pastoris (P. pastoris) G12’/AOX-acs2 strain to enhance SAM production was investigated using untargeted metabolomics and metabolic flux analysis. The results indicated that the addition of sodium citrate has a facilitative effect on SAM production. In addition, 25 metabolites, such as citrate, cis-aconitate, and L-glutamine, were significantly up-regulated, and 16 metabolites, such as glutathione, were significantly down-regulated. Furthermore, these significantly differential metabolites were mainly distributed in 13 metabolic pathways, such as the tricarboxylic acid (TCA) cycle. In addition, the metabolic fluxes of the glycolysis pathway, pentose phosphate pathway, TCA cycle, and glyoxylate pathway were increased by 20.45–29.32%, respectively, under the condition of feeding sodium citrate compared with the control. Finally, it was speculated that the upregulation of dihydroxyacetone level might increase the activity of alcohol oxidase AOX1 to promote methanol metabolism by combining metabolomics and fluxomics. Meanwhile, acetyl coenzyme A might enhance the activity of citrate synthase through allosteric activation to promote the flux of the TCA cycle and increase the level of intracellular oxidative phosphorylation, thus contributing to SAM production. These new insights into the L-methionine utilization for SAM biosynthesis by systematic biology in P. pastoris provides a novel vision for increasing its industrial production.

Citric Acid in Rice Root Exudates Enhanced the Colonization and Plant Growth-Promoting Ability of Bacillus altitudinis LZP02.

Exploration of the underlying mechanisms of plant-microbe interactions is very important. In the present study, citric acid in the root exudates of rice significantly enhanced the colonization of Bacillus altitudinis LZP02 in the rhizosphere. According to the results of transcriptome and reverse transcription-quantitative PCR or analyses, citric acid increased the expression of several genes involved in bacterial chemotaxis and biofilm formation in B. altitudinis LZP02. In addition, citric acid also increased the expression of several genes associated with S-adenosylmethionine biosynthesis and metabolism. Interestingly, the secretion of citric acid by rice roots could be increased by inoculation with B. altitudinis LZP02. The result indicated that citric acid might be a vital signal in the interaction between rice and B. altitudinis LZP02. Further verification showed that citric acid enhanced the plant growth-promoting ability of B. altitudinis LZP02. IMPORTANCE In a previous study, the mechanism by which citric acid in rice root exudates enhanced the colonization of Bacillus altitudinis LZP02 was discovered. The present study verified that citric acid increased the recruitment and rice growth-promoting ability of B. altitudinis LZP02. These findings serve as an interesting case for explaining the underlying mechanisms of plant-microbe interactions. Henceforth, citric acid and B. altitudinis LZP02 could be exploited for the development of sustainable agronomy.

Identification of small molecules targeting homoserine acetyl transferase from Mycobacterium tuberculosis and Staphylococcus aureus

There is an urgent need to validate new drug targets and identify small molecules that possess activity against both drug-resistant and drug-sensitive bacteria. The enzymes belonging to amino acid biosynthesis have been shown to be essential for growth in vitro, in vivo and have not been exploited much for the development of anti-tubercular agents. Here, we have identified small molecule inhibitors targeting homoserine acetyl transferase (HSAT, MetX, Rv3341) from M. tuberculosis. MetX catalyses the first committed step in L-methionine and S-adenosyl methionine biosynthesis resulting in the formation of O-acetyl-homoserine. Using CRISPRi approach, we demonstrate that conditional repression of metX resulted in inhibition of M. tuberculosis growth in vitro. We have determined steady state kinetic parameters for the acetylation of L-homoserine by Rv3341. We show that the recombinant enzyme followed Michaelis–Menten kinetics and utilizes both acetyl-CoA and propionyl-CoA as acyl-donors. High-throughput screening of a 2443 compound library resulted in identification of small molecule inhibitors against MetX enzyme from M. tuberculosis. The identified lead compounds inhibited Rv3341 enzymatic activity in a dose dependent manner and were also active against HSAT homolog from S. aureus. Molecular docking of the identified primary hits predicted residues that are essential for their binding in HSAT homologs from M. tuberculosis and S. aureus. ThermoFluor assay demonstrated direct binding of the identified primary hits with HSAT proteins. Few of the identified small molecules were able to inhibit growth of M. tuberculosis and S. aureus in liquid cultures. Taken together, our findings validated HSAT as an attractive target for development of new broad-spectrum anti-bacterial agents that should be effective against drug-resistant bacteria.

P-116: S-adenosylmethionine biosynthesis is a targetable metabolic vulnerability in multiple myeloma

P-116: S-adenosylmethionine biosynthesis is a targetable metabolic vulnerability in multiple myeloma

Targeting the methionine-methionine adenosyl transferase 2A- S -adenosyl methionine axis for cancer therapy.

In this review, we summarize the biological roles of methionine, methionine adenosyl transferase 2A (MAT2A) and S -adenosyl methionine (SAM) in methylation reactions during tumorigenesis. Newly emerged inhibitors targeting the methionine-MAT2A-SAM axis will be discussed. SAM is the critical and global methyl-donor for methylation reactions regulating gene expression, and in mammalian cells, it is synthesized by MAT2A using methionine. Recent studies have validated methionine and MAT2A as metabolic dependencies of cancer cells because of their essential roles in SAM biosynthesis. MAT2A inhibition leads to synthetic lethality in methylthioadenosine-phosphorylase (MTAP)-deleted cancers, which accounts for 15% of all cancer types. Of note, remarkable progress has been made in developing inhibitors targeting the methionine-MAT2A-SAM axis, as the first-in-class MAT2A inhibitors AG-270 and IDE397 enter clinical trials to treat cancer. The methionine-MAT2A-SAM axis plays an important role in tumorigenesis by providing SAM as a critical substrate for abnormal protein as well as DNA and RNA methylation in cancer cells. Targeting SAM biosynthesis through MAT2A inhibition has emerged as a novel and promising strategy for cancer therapy.

Virulent Mycobacterium avium subspecies hominissuis subverts macrophages during early stages of infection.

Virulent non-tuberculous Mycobacteria (NTMs) successfully reside and multiply within the phagosomes of phagocytic cells such as monocytes and macrophages. Macrophages play a very important role in the innate clearance of intracellular pathogens including NTMs. Attenuated Mycobacterium avium subsp. hominissuis 100 enters macrophages but is incapable of escaping these cells via canonical mycobacteria escape mechanisms. Alternatively, virulent Mycobacterium avium subsp. hominissuis 104 and Mycobacterium abscessus subsp. abscessus are able to modify macrophages to suit their growth, survival and ultimately escape from macrophages, while non-virulent Mycobacterium smegmatis is readily killed by macrophages. In this study we focused on early infection of macrophages with NTMs to determine the phenotypic response of macrophages, M1 or M2 differentiation, and phosphorylation alterations that can affect cellular response to invading bacteria. Our findings indicate that infection of the macrophage with MAH 100 and M. smegmatis favours the development of M1 macrophage, a pro-inflammatory phenotype associated with the killing of intracellular pathogens, while infection of the macrophage with MAH 104 and M. abscessus favoured the development of M2 macrophage, an anti-inflammatory phenotype associated with the healing process. Interference with the host post-translational mechanisms, such as protein phosphorylation, is a key strategy used by many intracellular bacterial pathogens to modulate macrophage phenotype and subvert macrophage function. By comparing protein phosphorylation patterns of infected macrophages, we observed that uptake of both MAH 100 and M. smegmatis resulted in MARCKS-related protein phosphorylation, which has been associated with macrophage activation. In contrast, in macrophages infected with MAH 104 and M. abscessus, methionine adenosyltransferase IIβ, an enzyme that catalyses the biosynthesis of S-adenosylmethionine, a methyl donor for DNA methylation. Inhibition of DNA methylation with 5-aza-2 deoxycytidine, significantly impaired the survival of MAH 104 in macrophages. Our findings suggest that the virulent MAH 104 and M. abscessus enhance its survival in the macrophage possibly through interference with the epigenome responses.

S-adenosylmethionine inhibits la ribonucleoprotein domain family member 1 in murine liver and human liver cancer cells.

Methionine adenosyltransferase 1A (MAT1A) is responsible for S-adenosylmethionine (SAMe) biosynthesis in the liver. Mice lacking Mat1a have hepatic SAMe depletion and develop NASH and HCC spontaneously. Several kinases are activated in Mat1a knockout (KO) mice livers. However, characterizing the phospho-proteome and determining whether they contribute to liver pathology remain open for study. Our study aimed to provide this knowledge. We performed phospho-proteomics in Mat1a KO mice livers with and without SAMe treatment to identify SAMe-dependent changes that may contribute to liver pathology. Our studies used Mat1a KO mice at different ages treated with and without SAMe, cell lines, in vitro translation and kinase assays, and human liver specimens. We found that the most striking change was hyperphosphorylation and increased content of La-related protein 1 (LARP1), which, in the unphosphorylated form, negatively regulates translation of 5'-terminal oligopyrimidine (TOP)-containing mRNAs. Consistently, multiple TOP proteins are induced in KO livers. Translation of TOP mRNAs ribosomal protein S3 and ribosomal protein L18 was enhanced by LARP1 overexpression in liver cancer cells. We identified LARP1-T449 as a SAMe-sensitive phospho-site of cyclin-dependent kinase 2 (CDK2). Knocking down CDK2 lowered LARP1 phosphorylation and prevented LARP1-overexpression-mediated increase in translation. LARP1-T449 phosphorylation induced global translation, cell growth, migration, invasion, and expression of oncogenic TOP-ribosomal proteins in HCC cells. LARP1 expression is increased in human NASH and HCC. Our results reveal a SAMe-sensitive mechanism of LARP1 phosphorylation that may be involved in the progression of NASH to HCC.

Implications of divergence of methionine adenosyltransferase in archaea.

Methionine adenosyltransferase (MAT) catalyzes the biosynthesis of S‐adenosyl methionine from l‐methionine and ATP. MAT enzymes are ancient, believed to share a common ancestor, and are highly conserved in all three domains of life. However, the sequences of archaeal MATs show considerable divergence compared with their bacterial and eukaryotic counterparts. Furthermore, the structural significance and functional significance of this sequence divergence are not well understood. In the present study, we employed structural analysis and ancestral sequence reconstruction to investigate archaeal MAT divergence. We observed that the dimer interface containing the active site (which is usually well conserved) diverged considerably between the bacterial/eukaryotic MATs and archaeal MAT. A detailed investigation of the available structures supports the sequence analysis outcome: The protein domains and subdomains of bacterial and eukaryotic MAT are more similar than those of archaea. Finally, we resurrected archaeal MAT ancestors. Interestingly, archaeal MAT ancestors show substrate specificity, which is lost during evolution. This observation supports the hypothesis of a common MAT ancestor for the three domains of life. In conclusion, we have demonstrated that archaeal MAT is an ideal system for studying an enzyme family that evolved differently in one domain compared with others while maintaining the same catalytic activity.