Latasa, M.U. (María Ujué)

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    Identification of argininosuccinate lyase as a hypoxia-responsive gene in rat hepatocytes
    (Elsevier, 2000) Latasa, M.U. (María Ujué); Avila, M.A. (Matías Antonio); Carretero, M.V. (M. Victoria); Ruiz Garcia-Trevijano, E. (Elena); Torres, L. (Luis); Mato, J.M. (José María)
    BACKGROUND/AIMS: The differential oxygenation of periportal and perivenous hepatocytes has been demonstrated as a major determinant in the zonated expression of certain metabolic pathways in the liver. We have searched for novel genes whose expression could be modulated by hypoxia in cultured rat hepatocytes. METHODS: Primary cultures of rat hepatocytes were incubated under normoxic (21% oxygen) or hypoxic (3% oxygen) conditions for 6 h. Differences in gene expression under both conditions were analyzed using the technique of differential display by means of PCR. RESULTS: We have identified the enzyme argininosuccinate lyase (ASL) as being downregulated by hypoxia. ASL is a cytosolic protein which participates in urea metabolism. ASL expression was time-dependently reduced in hypoxia. Hypoxia modulated the responses of this gene to the two main hormonal signals which induce ASL mRNA: glucocorticoids and cAMP. ASL mRNA levels decreased in response to ATP-reducing agents. CoCl2 mimicked the effect of hypoxia, suggesting the implication of a hemoprotein in this response. Hypoxia did not affect ASL mRNA stability, indicating that this effect occurs at the transcriptional level. CONCLUSIONS: Our observations suggest that differences in oxygen levels across the hepatic parenchyma could participate in the zonated expression of ASL.
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    Liver-specific methionine adenosyltransferase MAT1A gene expression is associated with a specific pattern of promoter methylation and histone acetylation: implications for MAT1A silencing during transformation
    (Federation of American Society of Experimental Biology, 2000) Latasa, M.U. (María Ujué); Boukaba, A. (Abdelhalim); Lopez-Rodas, G. (Gerardo); Lu, S.C. (Shelly C.); Avila, M.A. (Matías Antonio); Carretero, M.V. (M. Victoria); Torres, L. (Luis); Franco, L. (Luis); Caballeria, J. (Juan); Mato, J.M. (José María)
    Methionine adenosyltransferase (MAT) is the enzyme that catalyzes the synthesis of S-adenosylmethionine (AdoMet), the main donor of methyl groups in the cell. In mammals MAT is the product of two genes, MAT1A and MAT2A. MAT1A is expressed only in the mature liver whereas fetal hepatocytes, extrahepatic tissues and liver cancer cells express MAT2A. The mechanisms behind the tissue and differentiation state specific MAT1A expression are not known. In the present work we examined MAT1A promoter methylation status by means of methylation sensitive restriction enzyme analysis. Our data indicate that MAT1A promoter is hypomethylated in liver and hypermethylated in kidney and fetal rat hepatocytes, indicating that this modification is tissue specific and developmentally regulated. Immunoprecipitation of mononucleosomes from liver and kidney tissues with antibodies mainly specific to acetylated histone H4 and subsequent Southern blot analysis with a MAT1A promoter probe demonstrated that MAT1A expression is linked to elevated levels of chromatin acetylation. Early changes in MAT1A methylation are already observed in the precancerous cirrhotic livers from rats, which show reduced MAT1A expression. Human hepatoma cell lines in which MAT1A is not expressed were also hypermethylated at this locus. Finally we demonstrate that MAT1A expression is reactivated in the human hepatoma cell line HepG2 treated with 5-aza-2'-deoxycytidine or the histone deacetylase inhibitor trichostatin, suggesting a role for DNA hypermethylation and histone deacetylation in MAT1A silencing.
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    Identification and experimental validation of druggable epigenetic targets in hepatoblastoma
    (Elsevier, 2023) Indersie, E. (Emilie); Latasa, M.U. (María Ujué); Berraondo, P. (Pedro); Corrales, F.J. (Fernando José); Berasain, C. (Carmen); Arechederra, M. (María); Domingo-Sàbat, M. (Montserrat); Pineda-Lucena, A. (Antonio); Sancho-Bru, P. (Pau); Zanatto, L. (Laura); Armengol, C. (Carolina); Uriarte, I. (Iker); Ciordia, S. (Sergio); Avila, M.A. (Matías Antonio); Alaggio, R. (Rita); Alonso, C. (Cristina); Sangro, B. (Bruno); García-Fernandez-Barrena, M. (Maite); Herranz, J.M. (José M.); Cairo, S. (Stefano); García-Marin, J.J. (Jose Juan); Francalanci, P. (Paola); Prosper-Cardoso, F. (Felipe); Claveria-Cabello, A. (Alex); Martinez-Chantar, M.L. (María Luz); Zucman-Rossi, J. (Jessica)
    Background & Aims: Hepatoblastoma (HB) is the most frequent childhood liver cancer. Patients with aggressive tumors have limited therapeutic options; therefore, a better understanding of HB pathogenesis is needed to improve treatment. HBs have a very low mutational burden; however, epigenetic alterations are increasingly recognized. We aimed to identify epigenetic regulators consistently dysregulated in HB and to evaluate the therapeutic efficacy of their targeting in clinically relevant models. Methods: We performed a comprehensive transcriptomic analysis of 180 epigenetic genes. Data from fetal, pediatric, adult, peritumoral (n = 72) and tumoral (n = 91) tissues were integrated. Selected epigenetic drugs were tested in HB cells. The most relevant epigenetic target identified was validated in primary HB cells, HB organoids, a patient-derived xenograft model, and a genetic mouse model. Transcriptomic, proteomic and metabolomic mechanistic analyses were performed. Results: Altered expression of genes regulating DNA methylation and histone modifications was consistently observed in association with molecular and clinical features of poor prognosis. The histone methyltransferase G9a was markedly upregulated in tumors with epigenetic and transcriptomic traits of increased malignancy. Pharmacological targeting of G9a significantly inhibited growth of HB cells, organoids and patient-derived xenografts. Development of HB induced by oncogenic forms of b-catenin and YAP1 was ablated in mice with hepatocyte-specific deletion of G9a. We observed that HBs undergo significant transcriptional rewiring in genes involved in amino acid metabolism and ribosomal biogenesis. G9a inhibition counteracted these pro-tumorigenic adaptations. Mechanistically, G9a targeting potently repressed the expression of c-MYC and ATF4, master regulators of HB metabolic reprogramming. Conclusions: HBs display a profound dysregulation of the epigenetic machinery. Pharmacological targeting of key epigenetic effectors exposes metabolic vulnerabilities that can be leveraged to improve the treatment of these patients.
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    Inhibition of liver methionine adenosyltransferase gene expression by 3-methylcolanthrene: protective effect of S-adenosylmethionine
    (Elsevier, 2001) Latasa, M.U. (María Ujué); Corrales, F.J. (Fernando José); Avila, M.A. (Matías Antonio); Wagner, C. (Conrad); Carretero, M.V. (M. Victoria); Ruiz Garcia-Trevijano, E. (Elena); Mato, J.M. (José María)
    Methionine adenosyltransferase (MAT) is an essential enzyme that catalyzes the synthesis of S-adenosylmethionine (AdoMet), the most important biological methyl donor. Liver MAT I/III is the product of the MAT1A gene. Hepatic MAT I/III activity and MAT1A expression are compromised under pathological conditions such as alcoholic liver disease and hepatic cirrhosis, and this gene is silenced upon neoplastic transformation of the liver. In the present work, we evaluated whether MAT1A expression could be targeted by the polycyclic arylhydrocarbon (PAH) 3-methylcholanthrene (3-MC) in rat liver and cultured hepatocytes. MAT1A mRNA levels were reduced by 50% following in vivo administration of 3-MC to adult male rats (100 mg/kg, p.o., 4 days' treatment). This effect was reproduced in a time- and dose-dependent fashion in cultured rat hepatocytes, and was accompanied by the induction of cytochrome P450 1A1 gene expression. This action of 3-MC was mimicked by other PAHs such as benzo[a]pyrene and benzo[e]pyrene, but not by the model arylhydrocarbon receptor (AhR) activator 2,3,7,8-tetrachlorodibenzo-p-dioxin. 3-MC inhibited transcription driven by a MAT1A promoter-reporter construct transfected into rat hepatocytes, but MAT1A mRNA stability was not affected. We recently showed that liver MAT1A expression is induced by AdoMet in cultured hepatocytes. Here, we observed that exogenously added AdoMet prevented the negative effects of 3-MC on MAT1A expression. Taken together, our data demonstrate that liver MAT1A gene expression is targeted by PAHs, independently of AhR activation. The effect of AdoMet may be part of the protective action of this molecule in liver damage.
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    Activation of the unfolded protein response (UPR) is associated with cholangiocellular injury, fibrosis and carcinogenesis in an experimental model of fibropolycystic liver disease
    (2022) Latasa, M.U. (María Ujué); Bañares, R. (Rafael); Berasain, C. (Carmen); Arechederra, M. (María); Fernández-Barrena, M.G. (Maite G.); Nevzorova, Y. (Yulia); Peligros, M.I. (María Isabel); Nelson, L.J. (Leonard J.); Avila, M.A. (Matías Antonio); Davis, R.J. (Roger J.); Tortajada, A. (Agustín); Wu, H. (Hanghang); Vidal, A. (August); Rodriguez-Perales, S. (Sandra); Ye, H. (Hui); Reissing, J. (Johanna); Mohamed, M.R. (Mohamed Ramadan); Iraburu-Elizalde, M. (María); Lujambio, A. (Amaya); Martínez-Naves, E. (Eduardo); Trautwein, C. (Christian); Villanueva, A. (Alberto); Vaquero, J. (Javier); Colyn, L. (Leticia); Torres-Ruiz, R. (Raúl); Zheng, K. (Kang); Bruns, T. (Tony); Cubero, F.J. (Francisco Javier); Chen, C. (Chaobo)
    Polycystic liver disease (PLD) is a group of rare disorders that result from structural changes in the biliary tree development in the liver. In the present work, we studied alterations in molecular mechanisms and signaling pathways that might be responsible for these pathologies. We found that activation of the unfolded protein response, a process that occurs in response to an accumulation of unfolded or misfolded proteins in the lumen of the endoplasmic reticulum, as well as the scarring of the liver tissue, contribute to the pathogenesis of PLD and the development of cancer. As a preclinical animal model we have used mutant mice of a specific signaling pathway, the c-Jun N-terminal kinase 1/2 (Jnk1/2). These mice resemble a perfect model for the study of PLD and early cancer development.
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    NO sensitizes rat hepatocytes to proliferation by modifying S-adenosylmethionine levels
    (WB Saunders, 2002) Latasa, M.U. (María Ujué); Avila, M.A. (Matías Antonio); Ruiz Garcia-Trevijano, E. (Elena); Mato, J.M. (José María); Martinez-Chantar, M.L. (María Luz)
    BACKGROUND & AIMS: Liver regeneration is a fundamental response of this organ to injury. Hepatocyte proliferation is triggered by growth factors, such as hepatocyte growth factor. However, hepatocytes need to be primed to react to mitogenic signals. It is known that nitrous oxide (NO), generated after partial hepatectomy, plays an important role in hepatocyte growth. Nevertheless, the molecular mechanisms behind this priming event are not completely known. S-adenosylmethionine (AdoMet) synthesis by methionine adenosyltransferase is the first step in methionine metabolism, and NO regulates hepatocyte S-adenosylmethionine levels through specific inhibition of this enzyme. We have studied the modulation of hepatocyte growth factor-induced proliferation by NO through the regulation of S-adenosylmethionine levels. METHODS: Studies were conducted in cultured rat hepatocytes isolated by collagenase perfusion, which triggers NO synthesis. RESULTS: The mitogenic response to hepatocyte growth factor was blunted when inducible NO synthase was inhibited; this process was overcome by the addition of an NO donor. This effect was dependent on methionine concentration in culture medium and intracellular S-adenosylmethionine levels. Accordingly, we found that S-adenosylmethionine inhibits hepatocyte growth factor-induced cyclin D1 and D2 expression, activator protein 1 induction, and hepatocyte proliferation. CONCLUSIONS: Together our findings indicate that NO may switch hepatocytes into a hepatocyte growth factor-responsive state through the down-regulation of S-adenosylmethionine levels.
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    Splicing factor SLU7 prevents oxidative stress-mediated hepatocyte nuclear factor 4α degradation, preserving hepatic differentiation and protecting from liver damage
    (Wiley, 2021) Latasa, M.U. (María Ujué); Corrales, F.J. (Fernando José); Berasain, C. (Carmen); Arechederra, M. (María); Pineda-Lucena, A. (Antonio); Uriarte, I. (Iker); Avila, M.A. (Matías Antonio); García-Ruiz, C. (Carmen); Azkona, M.T. (María Teresa); Sangro, B. (Bruno); Fernández-Checa, J.C. (José C.); Esquivel, A. (Argitxu); Raquel; Recalde, M. (Miriam); Gárate-Rascón, M. (María); García-Fernández-de-Barrena, M. (Maite); Elizalde, M. (María); Bilbao, I. (Idoia); Jiménez-Andrés, M. (Maddalen)
    Background and aims: Hepatocellular dedifferentiation is emerging as an important determinant in liver disease progression. Preservation of mature hepatocyte identity relies on a set of key genes, predominantly the transcription factor hepatocyte nuclear factor 4α (HNF4α) but also splicing factors like SLU7. How these factors interact and become dysregulated and the impact of their impairment in driving liver disease are not fully understood. Approach and results: Expression of SLU7 and that of the adult and oncofetal isoforms of HNF4α, driven by its promoter 1 (P1) and P2, respectively, was studied in diseased human and mouse livers. Hepatic function and damage response were analyzed in wild-type and Slu7-haploinsufficient/heterozygous (Slu7+/- ) mice undergoing chronic (CCl4 ) and acute (acetaminophen) injury. SLU7 expression was restored in CCl4 -injured mice using SLU7-expressing adeno-associated viruses (AAV-SLU7). The hepatocellular SLU7 interactome was characterized by mass spectrometry. Reduced SLU7 expression in human and mouse diseased livers correlated with a switch in HNF4α P1 to P2 usage. This response was reproduced in Slu7+/- mice, which displayed increased sensitivity to chronic and acute liver injury, enhanced oxidative stress, and marked impairment of hepatic functions. AAV-SLU7 infection prevented liver injury and hepatocellular dedifferentiation. Mechanistically we demonstrate a unique role for SLU7 in the preservation of HNF4α1 protein stability through its capacity to protect the liver against oxidative stress. SLU7 is herein identified as a key component of the stress granule proteome, an essential part of the cell's antioxidant machinery. Conclusions: Our results place SLU7 at the highest level of hepatocellular identity control, identifying SLU7 as a link between stress-protective mechanisms and liver differentiation. These findings emphasize the importance of the preservation of hepatic functions in the protection from liver injury.
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    Methionine adenosyltransferase II beta subunit gene expression provides a proliferative advantage in human hepatoma
    (WB Saunders, 2003) Latasa, M.U. (María Ujué); Martin-Duce, A. (Antonio); Avila, M.A. (Matías Antonio); Ruiz Garcia-Trevijano, E. (Elena); Fortes, P. (Puri); Caballeria, J. (Juan); Mato, J.M. (José María); Martinez-Chantar, M.L. (María Luz)
    BACKGROUND & AIMS: Of the 2 genes (MAT1A, MAT2A) encoding methionine adenosyltransferase, the enzyme that synthesizes S-adenosylmethionine, MAT1A, is expressed in liver, whereas MAT2A is expressed in extrahepatic tissues. In liver, MAT2A expression associates with growth, dedifferentiation, and cancer. Here, we identified the beta subunit as a regulator of proliferation in human hepatoma cell lines. The beta subunit has been cloned and shown to lower the K(m) of methionine adenosyltransferase II alpha2 (the MAT2A product) for methionine and to render the enzyme more susceptible to S-adenosylmethionine inhibition. METHODS: Methionine adenosyltransferase II alpha2 and beta subunit expression was analyzed in human and rat liver and hepatoma cell lines and their interaction studied in HuH7 cells. beta Subunit expression was up- and down-regulated in human hepatoma cell lines and the effect on DNA synthesis determined. RESULTS: We found that beta subunit is expressed in rat extrahepatic tissues but not in normal liver. In human liver, beta subunit expression associates with cirrhosis and hepatoma. beta Subunit is expressed in most (HepG2, PLC, and Hep3B) but not all (HuH7) hepatoma cell lines. Transfection of beta subunit reduced S-adenosylmethionine content and stimulated DNA synthesis in HuH7 cells, whereas down-regulation of beta subunit expression diminished DNA synthesis in HepG2. The interaction between methionine adenosyltransferase II alpha2 and beta subunit was demonstrated in HuH7 cells. CONCLUSIONS: Our findings indicate that beta subunit associates with cirrhosis and cancer providing a proliferative advantage in hepatoma cells through its interaction with methionine adenosyltransferase II alpha2 and down-regulation of S-adenosylmethionine levels.
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    Comprehensive analysis of epigenetic and epitranscriptomic genes’ expression in human NAFLD
    (Springer, 2023) Latasa, M.U. (María Ujué); Lopez-Pascual, A. (Amaya); Berasain, C. (Carmen); Arechederra, M. (María); Fernández-Barrena, M.G. (Maite G.); Uriarte, I. (Iker); Irigaray-Miramon, A. (Ainara); Avila, M.A. (Matías Antonio); Sangro, B. (Bruno); Herranz, J.M. (José M.); Adán-Villaescusa, E. (Elena); Castelló-Uribe, B. (Borja); Claveria-Cabello, A. (Alex)
    Non-alcoholic fatty liver disease (NAFLD) is a multifactorial condition with a complex etiology. Its incidence is increasing globally in parallel with the obesity epidemic, and it is now considered the most common liver disease in Western countries. The precise mechanisms underlying the development and progression of NAFLD are complex and still poorly understood. The dysregulation of epigenetic and epitranscriptomic mechanisms is increasingly recognized to play pathogenic roles in multiple conditions, including chronic liver diseases. Here, we have performed a comprehensive analysis of the expression of epigenetic and epitranscriptomic genes in a total of 903 liver tissue samples corresponding to patients with normal liver, obese patients, and patients with non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH), advancing stages in NAFLD progression. We integrated ten transcriptomic datasets in an unbiased manner, enabling their robust analysis and comparison. We describe the complete landscape of epigenetic and epitranscriptomic genes’ expression along the course of the disease. We identify signatures of genes significantly dysregulated in association with disease progression, particularly with liver fibrosis development. Most of these epigenetic and epitranscriptomic effectors have not been previously described in human NAFLD, and their altered expression may have pathogenic implications. We also performed a comprehensive analysis of the expression of enzymes involved in the metabolism of the substrates and cofactors of epigenetic and epitranscriptomic effectors. This study provides novel information on NAFLD pathogenesis and may also guide the identification of drug targets to treat this condition and its progression towards hepatocellular carcinoma.
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    Redox regulation of methylthioadenosine phosphorylase in liver cells: molecular mechanism and functional implications
    (Portland Press, 2008) Latasa, M.U. (María Ujué); Corrales, F.J. (Fernando José); Sanchez-del-Pino, M.M. (Manuel M.); Avila, M.A. (Matías Antonio); Sanchez-Quiles, V. (Virginia); Fernandez-Irigoyen, J. (Joaquín); Prieto, J. (Jesús); Muñoz, J. (Javier); Santamaria, M. (Mónica); Santamaria, E. (Enrique); Valero, M.L. (María L.)
    MTAP (5'-methylthioadenosine phosphorylase) catalyses the reversible phosphorolytic cleavage of methylthioadenosine leading to the production of methylthioribose-1-phosphate and adenine. Deficient MTAP activity has been correlated with human diseases including cirrhosis and hepatocellular carcinoma. In the present study we have investigated the regulation of MTAP by ROS (reactive oxygen species). The results of the present study support the inactivation of MTAP in the liver of bacterial LPS (lipopolysaccharide)-challenged mice as well as in HepG2 cells after exposure to t-butyl hydroperoxide. Reversible inactivation of purified MTAP by hydrogen peroxide results from a reduction of V(max) and involves the specific oxidation of Cys(136) and Cys(223) thiols to sulfenic acid that may be further stabilized to sulfenyl amide intermediates. Additionally, we found that Cys(145) and Cys(211) were disulfide bonded upon hydrogen peroxide exposure. However, this modification is not relevant to the mediation of the loss of MTAP activity as assessed by site-directed mutagenesis. Regulation of MTAP by ROS might participate in the redox regulation of the methionine catabolic pathway in the liver. Reduced MTA (5'-deoxy-5'-methylthioadenosine)-degrading activity may compensate for the deficient production of the precursor S-adenosylmethionine, allowing maintenance of intracellular MTA levels that may be critical to ensure cellular adaptation to physiopathological conditions such as inflammation.