Reclaiming of Monoethanolamine (MEA) Used in Post-Combustion CO2-capture with Electrodialysis

AbstractHeat-stable salts (HSS) in amine-based solvents may lead to a long-term performance impairment of post-combustion CO2- capture process system. They can cause a loss of solvent capacity, corrosion, heat exchanger fouling, increased foaming or flooding, etc. The application of electrodialysis (ED) can be a possible cost effective technique for removal of HSS from degraded amine solutions. The paper presents the results of lab-scale ED experiments on HSS removal from synthetic degraded MEA solutions with different HSS content and CO2-loadings. The efficiency of ED-process for reclaiming of MEA solvent is shown. The influence of solvent CO2-loading on the specific energy consumption of ED-process is presented. The lab-scale data have been used for design and manufacturing of a pilot ED plant. Within the OCTAVIUS project it has been planned to test the ED-pilot plant at the EnBW post-combustion CO2 capture pilot plant

Understanding Solvent Degradation: A Study from Three Different Pilot Plants within the OCTAVIUS Project

Abstract Degradation of amines is one of the most important issues to be addressed for absorption-desorption based post-combustion CO2 capture. Several laboratory studies have been performed to identify the degradation products and understand the mechanisms of degradation. However, there seems to be a gap in knowledge from translating the lab scale studies to observations from the pilot campaigns. Moreover, the observations from different pilot plant campaigns can be quite different. The objective of this study is to compare the solvent degradation behavior from different campaigns and highlight their causes in terms of solvent metal content and ammonia emissions. Results from the following different pilot plants are evaluated: (a) TNO's CO2 capture plant at Maasvlakte, the Netherlands, (b) EnBW's CO2 capture plant at Heilbronn, Germany and (c) ENEL's CO2 capture plant at Brindisi, Italy. The different rate of oxidative degradation are correlated to the different operating conditions and layout of the pilot plants. Along with these results, kinetic models based on laboratory studies are used to compare the pilot plant observations, highlighting the differences between lab-scale studies and pilot plant studies

Promoter-Wide Hypermethylation of the Ribosomal RNA Gene Promoter in the Suicide Brain

BACKGROUND: Alterations in gene expression in the suicide brain have been reported and for several genes DNA methylation as an epigenetic regulator is thought to play a role. rRNA genes, that encode ribosomal RNA, are the backbone of the protein synthesis machinery and levels of rRNA gene promoter methylation determine rRNA transcription. METHODOLOGY/PRINCIPAL FINDINGS: We test here by sodium bisulfite mapping of the rRNA promoter and quantitative real-time PCR of rRNA expression the hypothesis that epigenetic differences in critical loci in the brain are involved in the pathophysiology of suicide. Suicide subjects in this study were selected for a history of early childhood neglect/abuse, which is associated with decreased hippocampal volume and cognitive impairments. rRNA was significantly hypermethylated throughout the promoter and 5' regulatory region in the brain of suicide subjects, consistent with reduced rRNA expression in the hippocampus. This difference in rRNA methylation was not evident in the cerebellum and occurred in the absence of genome-wide changes in methylation, as assessed by nearest neighbor. CONCLUSIONS/SIGNIFICANCE: This is the first study to show aberrant regulation of the protein synthesis machinery in the suicide brain. The data implicate the epigenetic modulation of rRNA in the pathophysiology of suicide

A method for purification, identification and validation of DNMT1 mRNA binding proteins

DNA methyltransferase 1 (DNMT1) is the enzyme responsible for the maintenance of DNA methylation patterns during cell division. DNMT1 expression is tightly regulated within the cell cycle. Our previous study showed that the binding of a protein with an apparent size of ~40 kDa on DNMT1 3’-UTR triggered the destabilization of DNMT1 mRNA transcript during Go/G1 phase. Using RNA affinity capture with the 3’-UTR of DNMT1 mRNA and matrix-assisted laser desorption-time of flight tandem mass spectrometry (MALDI-TOF-MS-MS) analysis, we isolated and identified AUF 1 (AU-rich element ARE:poly-(U)-binding/degradation factor) as the binding protein. We then validated the role of this protein in the destabilization of DNMT1 mRNA. In this report, we detail the different approaches used for the isolation, the identification of a RNA binding protein and the validation of its role

The role of DNMT1 regulation in cellular function

Disruption of the epigenome and its components is a hallmark of all forms of cancer. Typically observed in cancer is an alteration of the DNA methylation pattern, with silencing of tumour suppressor genes, as well as an increase in DNA methyltransferase 1 (activity or expression). However it has yet to be determined exactly how DNMT1 increases in cancer and how this increase might serve as therapeutic target. This thesis focuses on the regulation of DNMT1 in the cell cycle and the consequences of depleting DNMT1 in cancer cells.During the cell cycle DNMT1 levels increase as the cell enters into S-phase. It has previously been shown that this cyclical regulation of DNMT1 occurs by destabilization of DNMT1 mRNA in G0/G1 through the action of a protein, identified to be the mRNA binding protein AUF1. AUF1 binds a regulator element located in the 3'UTR of DNMT1 mRNA and recruits the exosome, the RNA degradation complex, to degrade it.When AUF1 is depleted in these cells, DNMT1 mRNA is stabilized which leads to increased DNMT1 protein levels, methyltransferase activity and genomic methylation. The changes of DNMT1 mRNA levels in the cell cycle were determined to occur as an inverse function of AUF1 protein levels. AUF1 levels were observed to decrease in S-phase which lead to increased stability in DNMT1 mRNA. This cell cycle regulation of AUF1 was determined to occur as a function of Rb. Rb actively stabilizes AUF1 protein. Indeed, upon elimination of Rb, AUF1 is degraded through the function of Hsp70 and the proteasome. This consequently leads to an elevation in DNMT1 protein levels which in turn increases genomic methylation levels. Elevated DNMT1 levels resulted in greater association with EZH2, which in turn leads to increased methylation of EZH2 targeted promoters, including p16 and CNR1. This promoter hypermethylation occurred as a function of DNMT1 and EZH2.These observations indicate that regulation of DNMT1 is tied into the cell cycle function of Rb and upon disruption of this system, a characteristic of cancer, site-specific methylation occurs at tumour suppressors, another characteristic of cancer.Furthermore, we examined the effect of depleting DNMT1 in cancer cells. Upon depletion of DNMT1, a signaling pathway known as the replication arrest/DNA damage checkpoint was induced. Activation of this pathway results in arrest of cell growth and cell cycle blockage and occurred independently of the catalytic activity of DNMT1 and instead responded to the absence of DNMT1. This supports a role for DMNT1 as a negative regulator of the replication arrest/DNA damage checkpoint through the action of interaction with an unknown protein. Moreover, suppression of the replication arrest/DNA damage checkpoint has been determined to be a necessary step in the proliferation of cancer cells. Taken together, the data from this thesis determined that common events in cancer, such as inactivation of Rb, lead to deregulation of DNMT1 mRNA, through AUF1, leading to site-specific methylation of tumour suppressors and could potentially serve to block growth arresting checkpoints like the replication arrest/DNA damage checkpoint. The novel functions of DNMT1, such as cell cycle regulation, site-specific methylation and role in the replication arrest/DNA damage checkpoint discovered in this thesis could serve to help better understand how cancer develops. The results of this thesis could serve to develop novel strategies to target these events and better treat cancer.L'altération de l'épigénome et de ses composants est une marque caractéristique de tous types de cancer. Une altération des profils de méthylation de l'ADN, associée à une inactivation de gènes suppresseurs de tumeurs ainsi qu'une augmentation de l'(activité/expression) de la méthyltransférase de l'ADN (DNMT1) sont largement observés dans les cancers. Cependant, les causes de cette augmentation de DNMT1 (expression/activité) dans le cancer et l'utilisation potentielle de cette augmentation comme cible thérapeutique n'ont pas encore été déterminées.Au cours du cycle cellulaire, le niveau de DNMT1 augmente dès lors que la cellule entre en phase S. Il a été montré précédemment qu'une régulation cyclique de DNMT1 se met en place grâce à une déstabilisation de son ARN messager en phase G0/G1 sous l'action d'une protéine non identifiée. Cette protéine a été identifié comme AUF1. AUF1 interagit avec un élément régulateur situé dans la partie 3'-UTR de l'ARNm de DNMT1 et entraîne la dégradation de cet ARNm en recrutant l'exosome, un complexe de dégradation de l'ARN. La déplétion d'AUF1 stabilise l'ARNm de DNMT1 ce qui conduit à une augmentation de l'expression de cette protéine, de son activité méthyltransférase ainsi que de la méthylation du génome. Il a été également montré que le niveau d'expression de l'ARNm de DNMT1 au cours du cycle cellulaire est inversement corrélé à celui de la protéine AUF1. Ce niveau d'AUF1 est diminué en phase S ce qui traduit par une stabilité accrue de l'ARNm de DNMT1. Il a été montré que cette régulation d'AUF1 au cours du cycle cellulaire est fonction de la protéine Rb. Rb stabilise activement la protéine AUF1. En effet, AUF1 est dégradée par l'intermédiaire de la protéine Hsp70 et du protéasome. Cette dégradation a pour conséquence une augmentation du niveau d'expression de DNMT1 lequel conduit à une augmentation du niveau de méthylation du génome. De plus, cette augmentation de DNMT1 résulte en une plus grande association avec la protéine EZH2 entraînant une hyperméthylation de promoteurs de gènes ciblés par EZH2 (ex : p16, CNR1 et PCNA). Ces observations démontrent que la régulation de DNMT1 est étroitement liée aux fonctions de Rb dans le cycle cellulaire. Caractéristique dans les cancers, une rupture de cette relation DNMT1-Rb, entraîne ainsi une méthylation site-spécifique de gènes suppresseurs de tumeurs, une autre caractéristique des cancers.En parallèle, nous avons étudié l'effet d'une déplétion de DNMT1 dans des cellules cancéreuses. Suite à une déplétion de DNMT1, une voie de signalisation connue comme un point de contrôle de l'arrêt de la réplication/lésions de l'ADN est induite. L'activation de cette voie de signalisation entraîne l'arrêt de la croissance cellulaire et le blocage du cycle cellulaire. L'activation de cette voie répond à l'absence de DNMT1 et de façon indépendante de son activité catalytique. Ceci est en faveur d'un rôle pour DNMT1 de régulateur négatif du contrôle de l'arrêt de la réplication/lésions de l'ADN via l'interaction avec une protéine qui reste encore à identifier. De plus, la suppression des points de contrôle de l'arrêt de la réplication/lésion de l'ADN a été montré comme étant une étape nécessaire à la prolifération des cellules cancéreuses. L'ensemble des données de cette thèse démontre que des événements communs aux cancers, telle que l'inactivation de Rb, peuvent conduire à la dérégulation, via AUF1, de l'ARNm de DNMT1, laquelle entraîne la méthylation site-spécifique de gènes suppresseurs de tumeurs. Cette dérégulation de DNMT1 pourrait potentiellement servir à bloquer les points de contrôle d'arrêt du cycle cellulaire/lésions de l'ADN.Les nouvelles fonctions de DNMT1, telles que la régulation du cycle cellulaire, la méthylation site-spécifique et le contrôle de la réplication/lésions de l'ADN découverts dans cette thèse devraient permettre de mieux comprendre le développement cancéreux et de développer de nouvelles stratégies thérapeutiques

Pharmacological Inhibition of DNA Methylation Induces Proinvasive and Prometastatic Genes In Vitro and In Vivo1

The mechanism of action of DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-aza-CdR), a potential anticancer agent is believed to be activated by the demethylation of tumor suppressor genes. We tested here the hypothesis that demethylating agents also demethylate and activate genes involved in invasion and metastasis and therefore might increase the risk of developing tumor metastasis. The effect of 5-aza-CdR on noninvasive human breast cancer cells MCF-7 and ZR-75-1 was evaluated by cell proliferation, invasion, and migration assay. The ability of 5-aza-CdR to activate a panel of silenced prometastatic and tumor suppressor genes was evaluated using reverse transcription-polymerase chain reaction and bisulfite DNA sequence analysis in vitro and for change in tumor growth and gene expression in vivo. Treatment of MCF-7 and ZR-75-1 with 5-aza-CdR diminished cell proliferation, induced tumor suppressor RASSF1A, and altered cell cycle kinetics' G2/M-phase cell cycle arrest. While these effects of 5-aza-CdR slowed the growth of tumors in nude mice, it also induced a battery of prometastatic genes, namely, uPA, CXCR4, HEPARANASE, SYNUCLEIN γ, and transforming growth factor-beta (TGF-β), by demethylation of their promoters. These results draw attention to the critical role of demethylation as a potential mechanism that can promote the development and progression of tumor metastasis after demethylation therapy as an anticancer treatment

AUF1 Cell Cycle Variations Define Genomic DNA Methylation by Regulation of DNMT1 mRNA Stability

DNA methylation is a major determinant of epigenetic inheritance. DNA methyltransferase 1 (DNMT1) is the enzyme responsible for the maintenance of DNA methylation patterns during cell division, and deregulated expression of DNMT1 leads to cellular transformation. We show herein that AU-rich element/poly(U)-binding/degradation factor 1 (AUF1)/heterogenous nuclear ribonucleoprotein D interacts with an AU-rich conserved element in the 3′ untranslated region of the DNMT1 mRNA and targets it for destabilization by the exosome. AUF1 protein levels are regulated by the cell cycle by the proteasome, resulting in cell cycle-specific destabilization of DNMT1 mRNA. AUF1 knock down leads to increased DNMT1 expression and modifications of cell cycle kinetics, increased DNA methyltransferase activity, and genome hypermethylation. Concurrent AUF1 and DNMT1 knock down abolishes this effect, suggesting that the effects of AUF1 knock down on the cell cycle are mediated at least in part by DNMT1. In this study, we demonstrate a link between AUF1, the RNA degradation machinery, and maintenance of the epigenetic integrity of the cell

DNA Methyltransferase 1 Knockdown Activates a Replication Stress Checkpoint

DNA methyltransferase 1 (DNMT1) is an important component of the epigenetic machinery and is responsible for copying DNA methylation patterns during cell division. Coordination of DNA methylation and DNA replication is critical for maintaining epigenetic programming. Knockdown of DNMT1 leads to inhibition of DNA replication, but the mechanism has been unclear. Here we show that depletion of DNMT1 with either antisense or small interfering RNA (siRNA) specific to DNMT1 activates a cascade of genotoxic stress checkpoint proteins, resulting in phosphorylation of checkpoint kinases 1 and 2 (Chk1 and -2), γH2AX focus formation, and cell division control protein 25a (CDC25a) degradation, in an ataxia telangiectasia mutated-Rad3-related (ATR)-dependent manner. siRNA knockdown of ATR blocks the response to DNMT1 depletion; DNA synthesis continues in the absence of DNMT1, resulting in global hypomethylation. Similarly, the response to DNMT1 knockdown is significantly attenuated in human mutant ATR fibroblast cells from a Seckel syndrome patient. This response is sensitive to DNMT1 depletion, independent of the catalytic domain of DNMT1, as indicated by abolition of the response with ectopic expression of either DNMT1 or DNMT1 with the catalytic domain deleted. There is no response to short-term treatment with 5-aza-deoxycytidine (5-aza-CdR), which causes demethylation by trapping DNMT1 in 5-aza-CdR-containing DNA but does not cause disappearance of DNMT1 from the nucleus. Our data are consistent with the hypothesis that removal of DNMT1 from replication forks is the trigger for this response

Factors for Effective Learning in Production Networks to Improve Environmental Performance

There is evidence that the environmental performances of factories operating under similar circumstances vary greatly, even within one company. This indicates that production sites are operated in different ways which suggests a potential for improvement. Previous research shows that collaboration within production networks can improve factory performance. Learning collaboratively across factories is a promising approach to reduce the environmental impact of production sites. Several companies recognised this opportunity. Processes and systems to support knowledge and know-how exchange within their production network are already in place. In this research a literature review and interviews were carried out to explore factors that influence learning between factories. Such factors are critical to develop an effective tool enabling learning across factories and thus environmental performance improvements