Mastermind-like 1 (MAML1) is a transcriptional coregulator that has been associated with early development of many systems such as neuronal, muscular and urogenital. The present study aimed to explore the genome wide effects of MAML1 on DNA methylation and RNA expression in human embryonic kidney cells. Infinium HumanMethylation450 BeadChip Illumina array, methylation-sensitive high-resolution melt technique, Chip Analysis Methylation Pipeline and RNA profiling approaches were used to study MAML1 effects on the epigenome. We found that 11802 CpG sites were differentially methylated in MAML1-expressing cells while only 225 genes were differentially expressed. MAML1 overexpression induced more global differential hypermethylation than hypomethylation changes. In addition, the differentially methylated regions were mapped predominantly to 3′untranslated regions, intragenic regions and gene bodies and to a lesser extent to gene regulatory sequences. Gene ontology analysis revealed that the differentially changed genes (including HOXC11, HTATIP2, SLFN12 and SOX11) are involved in the regulation of urogenital system development, cell adhesion and embryogenesis. This study is the first report that shows the global effect of a single coregulator on DNA methylation and gene expression. Our results stress and support the effects of transcriptional coregulators on the cell methylome.

Arsenic, an established carcinogen and toxicant, occurs in drinking water and food and affects millions of people worldwide. Arsenic appears to interfere with gene expression through epigenetic processes, such as DNA methylation and post-translational histone modifications. We investigated the effects of arsenic on histone residues in vivo as well as in vitro. Analysis of H3K9Ac and H3K9me3 in CD4+ and CD8+ sorted blood cells from individuals exposed to arsenic through drinking water in the Argentinean Andes showed a significant decrease in global H3K9me3 in CD4+ cells, but not CD8+ cells, with increasing arsenic exposure. In vitro studies of inorganic arsenic-treated T lymphocytes (Jurkat and CCRF-CEM, 0.1, 1, and 100 μg/L) showed arsenic-related modifications of H3K9Ac and changes in the levels of the histone deacetylating enzyme HDAC2 at very low arsenic concentrations. Further, in vitro exposure of kidney HEK293 cells to arsenic (1 and 5 μM) altered the protein levels of PCNA and DNMT1, parts of a gene expression repressor complex, as well as MAML1. MAML1 co-localized and interacted with components of this complex in HEK293 cells, and in silico studies indicated that MAML1 expression correlate with HDAC2 and DNMT1 expression in kidney cells. In conclusion, our data suggest that arsenic exposure may lead to changes in the global levels of H3K9me3 and H3K9Ac in lymphocytes. Also, we show that arsenic exposure affects the expression of PCNA and DNMT1-proteins that are part of a gene expression silencing complex.

Early studies demonstrated the involvement of ubiquitination of the Notch intracellular domain for rapid turnover of the transcriptional complex at Notch target genes. It was shown that this ubiquitination was promoted by the co-activator Mastermind like 1 (MAML1). MAML1 also contains numerous lysine residues that may also be ubiquitinated and necessary for protein regulation. In this study, we show that over-expressed MAML1 is ubiquitinated and identify eight conserved lysine residues which are required for ubiquitination. We also show that p300 stimulates ubiquitination and that Notch inhibits ubiquitination. Furthermore, we show that a mutant MAML1 that has decreased ubiquitination shows increased output from a HES1 reporter gene assay. Therefore, we speculate that ubiquitination of MAML1 might be a mechanism to maintain low levels of the protein until needed for transcriptional activation. In summary, this study identifies that MAML1 is ubiquitinated in the absence of Notch signaling to maintain low levels of MAML1 in the cell. Our data supports the notion that a precise and tight regulation of the Notch pathway is required for this signaling pathway.

Immortalized cell lines are widely used in genetic and epigenetic studies, from exploration of basic molecular pathways to evaluation of disease-specific cellular properties. They are also used in biotechnology, e.g., in drug toxicity tests and vaccine production. Cellular and genetic uniformity is the main feature of immortalized cell lines and it has been particularly advantageous in functional genomic research, which has in recent years been expanded to include epigenetic mechanisms of gene expression regulation. Using the MS-HRM technique, we demonstrated heterogeneity in locus-specific methylation patterns in different cell cultures of four human cell lines: HEK293, HEK293T, LCL and DU145. Our results show that some human immortalized cell lines consist of cells that differ in the methylation status of specific loci, i.e., that they are epigenetically heterogeneous. We show that even two cultures of the same cell line obtained from different laboratories can differ in the methylation status of the specific loci. The results indicated that epigenetic uniformity of the cell lines cannot be assumed in experiments which utilize cell cultures and that the methylation status of the specific loci in the immortalized cell lines should be re-characterized and carefully profiled before epigenetic studies are performed.

Mastermind-like 1 (MAML1) is a transcriptional coregulator of diverse/multiple activators, such as Notch, p53, myocyte enhancer factor 2C, NF-κB, beta-catenin, papillomavirus E6 proteins, early growth response 1 and runt-related transcription factor 2. Thus, MAML1 functions in various signaling pathways, most of them connected to cell proliferation, which suggests that MAML1 might play a potential role as a cell proliferation marker. In this study we show that MAML1 expression in the kidney correlates in silico with established cell proliferation markers including PCNA, CDC2 and XRCC5 (Ku80). Over-expression of MAML1 increased proliferation of human embryonic kidney (HEK) 293 cells, while MAML1 downregulation by siRNA decreased cell proliferation. Exposure of HEK293 cells to inorganic arsenic (arsenite) showed reduced levels of MAML1, in combination with a decreased proliferation rate. Our findings provide evidence that arsenic can inhibit proliferation of embryonic kidney cells, possibly through reduction of MAML1 gene expression.

Abstract Dendrimers constitute structurally well-defined nanomaterials that are potentially useful for a vast range of biomedical applications, including targeted cancer therapy. Polyamidoamine (PAMAM) dendrimers are a relatively unexplored material subclass from consideration of low-dose studies of toxicological and biological effects, including epigenetic changes that may link to altered cell differentiation and risk of transformation. The present study assessed cell viability, histone modifications, genome-wide DNA methylation and gene expression changes in primary human bronchial epithelial cells (PBEC) and the human alveolar epithelial cell line A549 following exposure to 4th generation PAMAM dendrimers with hydroxyl (-OH) or amino (-NH2) terminating groups. The preliminary results show that these PAMAMs can regulate DNA methylation and histone modification at micromolar levels without significant effect on cell viability (lactate dehydrogenase assay). Specific changes in DNA methylation patterns implicated inflammation-related genes, although with different results in the two model systems. The results imply epigenetic regulation of gene expression by PAMAMs, and follow up work now investigates this hypothesis. Close attention to safety issues is of paramount importance for the sustainable development of the nanotechnologies, especially for biomedical applications, and the present data may shed light on potential long-term/low-dose effects of engineered nanomaterials. Citation Format: Pekka J. Kohonen, Neus T. Feliu, Lena Palmberg, Hanna L. Karlsson, Annika E. Wallberg, Roland C. Grafström, Bengt Fadeel. Polyamidoamine dendrimers induce epigenetic changes in cultured normal and malignant human lung epithelial cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5657. doi:10.1158/1538-7445.AM2013-5657

The t(1;19) translocation in pediatric pre-B-cell acute lymphoblastic leukemia (ALL) fuses the genes, which encode the transcriptional activator E2A and homeobox pre-B-cell leukemia transcription factor 1 (PBX1), resulting in expression of the chimeric transcription factor E2A-PBX1. E2A-PBX1 can promote cell transformation both in vitro and in vivo; however, the mechanisms by which E2A-PBX1 contributes to malignancy merit further investigation. In the current work we report, for the first time, a physical and functional interaction between the SPT3-TAFII31-GCN5L acetylase (STAGA) complex and E2A-PBX1. STAGA, and its acetyltransferase subunit GCN5, directly interacted with the E2A portion of E2A-PBX1. GCN5 acetylated E2A-PBX1 and increased the stability of E2A-PBX1 protein in cells. Moreover, the GCN5 inhibitor α-methylene-γ-butyrolactone 3 (MB-3) decreased E2A-PBX1 acetylation and E2A-PBX1 protein levels in leukemic cells, indicating that GCN5 inhibitors have potential value as therapeutic agents for ALL. In addition, we show that the E3 ubiquitin ligase HDM2 potentiates the degradation of E2A-PBX1. We suggest that dynamic regulation of E2A-PBX1 protein levels in vivo has a fundamental role in ALL.

Papillomavirus E6 oncoproteins associate with LXXLL motifs on target cellular proteins to alter their function. Using a proteomic approach, we found the E6 oncoproteins of cutaneous papillomaviruses Bovine Papillomavirus Type 1 (BPV-1) E6 and human papillomavirus (HPV) types 1 and 8 (1E6 and 8E6) associated with the MAML1 transcriptional co-activator. All three E6 proteins bind to an acidic LXXLL motif at the carboxy-terminus of MAML1 and repress transactivation by MAML1. MAML1 is best known as the co-activator and effector of NOTCH-induced transcription, and BPV-1 E6 represses synthetic NOTCH-responsive promoters, endogenous NOTCH-responsive promoters, and is found in a complex with MAML1 in stably transformed cells. BPV-1-induced papillomas show characteristics of repressed NOTCH signal transduction, including suprabasal expression of integrins, talin and basal type keratins, and delayed expression of the NOTCH-dependent HES1 transcription factor. These observations give rise to a model whereby papillomavirus oncoproteins, including BPV-1 E6, and the cancer-associated HPV-8 E6 repress NOTCH-induced transcription, thereby delaying keratinocyte differentiation.

In this study, cotton fabric was successfully coated with silver to have both antibacterial and conductive properties through a facile thermal reduction process at a low temperature using silver 2-ethylhexylcarbamate as the starting material. The cotton fabric modified with 3-mercaptopropyltriethoxysilane was padded with a solution of silver 2-ethylhexylcarbamate in methanol and then reduced for the in situ generation of Ag nanoparticles by only heating at 130 °C. The silver-coated cotton fabrics (cotton/Ag) were examined by a scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analyses. The morphology of cotton/Ag nanocomposite fabrics conveyed a uniform and continuous layer of silver metal on the cotton surface. The results indicated that the silver nanoparticles were assembled on cotton fibers with a size range from 20 to 100 nm. The cotton/Ag imparts high conductivity to the textiles with electric resistance as low as 3.92 ± 0.18 Ω. The antibacterial effects of the treated cotton fabric against Escherichia coli O157:H7 (ATCC 43889) and Staphylococcus aureus (ATCC 25923) were examined and found to be excellent.

Mastermind-like 1 (MAML1) is a transcriptional coregulator of activators in various signaling pathways, such as Notch, p53, myocyte enhancer factor 2C (MEF2C) and beta-catenin. In earlier studies, we demonstrated that MAML1 enhanced p300 acetyltransferase activity, which increased the acetylation of Notch by p300. In this study, we show that MAML1 strongly induced acetylation of the transcription factor early growth response-1 (EGR1) by p300, and increased EGR1 protein expression in embryonic kidney cells. EGR1 mRNA transcripts were also upregulated in the presence of MAML1. We show that MAML1 physically interacted with, and acted cooperatively with EGR1 to increase transcriptional activity of the EGR1 and p300 promoters, which both contain EGR1 binding sites. Bioinformatics assessment revealed a correlation between p300, EGR1 and MAML1 copy number and mRNA alterations in renal clear cell carcinoma and p300, EGR1 and MAML1 gene alterations were associated with increased overall survival. Our findings suggest MAML1 may be a component of the transcriptional networks which regulate EGR1 target genes during nephrogenesis and could also have implications for the development of renal cell carcinoma.

Earlier studies demonstrated the involvement of the p300 histone acetyltransferase in Notch signaling but the precise mechanisms by which p300 might modulate Notch function remains to be investigated. In this study, we show that p300 acetylates Notch1 ICD in cell culture assay and in vitro, and conserved lysines located within the Notch C-terminal nuclear localization signal are essential for Notch acetylation. MAML1 and CSL, which are components of the Notch transcription complex, enhance Notch acetylation and we suggest that MAML1 increases Notch acetylation by potentiating p300 autoacetylation. Furthermore, MAML1-dependent acetylation of Notch1 ICD by p300 decreases the ubiquitination of Notch1 ICD in cellular assays. CDK8 has been shown to target Notch1 for ubiquitination and proteosomal degradation. We show that CDK8 inhibits Notch acetylation and Notch transcription enhanced by p300. Therefore, we speculate that acetylation of Notch1 might be a mechanism to regulate Notch activity by interfering with ubiquitin-dependent pathways.

The Mastermindlike ( MAML) family, comprising human MAML1, MAML2, and MAML3, are transcriptional regulators in Notch signaling. MAML proteins contain two consensus sites for SUMOylation at Lysine217 and Lysine299 that are conserved in humans, mice, and Xenopus. In this report, we show that MAML1 is SUMOylated at both sites. The E2-conjugating enzyme UBC9 is essential for MAML1 SUMOylation, and the E3 ligase PIAS1 stimulates this activity. Mutation of the lysines abolishes SUMOylation of MAML1 and strongly increases MAML1-activated transcription in cell culture assays. The protease SENP1 reverses SUMOylation of MAML1 and potentiates the transcription factor activity of MAML1. Furthermore, SUMOylation enhances MAML1 interaction with HDAC7, which decreases MAML1 transcriptional activity. Taken together, our data indicate that SUMOylation of MAML1 is a mechanism for repressing MAML1 activity by influencing its interaction with HDAC7.-Lindberg, M.J., Popko-Scibor, A.E., Hansson, M.L., Wallberg, A. E. SUMO modification regulates the transcriptional activity of MAML1. FASEB J. 24, 2396-2404 (2010). www.fasebj.org

Glycogen synthase kinase 3β (GSK3β) is involved in several cellular signaling systems through regulation of the activity of diverse transcription factors such as Notch, p53 and β-catenin. Mastermind-like 1 (MAML1) was originally identified as a Notch coactivator, but has also been reported to function as a transcriptional coregulator of p53, β-catenin and MEF2C. In this report, we show that active GSK3β directly interacts with the MAML1 N-terminus and decreases MAML1 transcriptional activity, suggesting that GSK3β might target a coactivator in its regulation of gene expression. We have previously shown that MAML1 increases global acetylation of histones, and here we show that the GSK3 inhibitor SB41, further enhances MAML1-dependent histone acetylation in cells. Finally, MAML1 translocates GSK3β to nuclear bodies; this function requires full-length MAML1 protein.

MAML1 is a transcriptional coregulator originally identified as a Notch coactivator. MAML1 is also reported to interact with other coregulator proteins, such as CDK8 and p300, to modulate the activity of Notch. We, and others, previously showed that MAML1 recruits p300 to Notch-regulated genes through direct interactions with the DNACSLNotch complex and p300. MAML1 interacts with the C/H3 domain of p300, and the p300MAML1 complex specifically acetylates lysines of histone H3 and H4 tails in chromatin in vitro. In this report, we show that MAML1 potentiates p300 autoacetylation and p300 transcriptional activation. MAML1 directly enhances p300 HAT activity, and this coincides with the translocation of MAML1, p300 and acetylated histones to nuclear bodies.

The Mastermind-like (MAML) proteins are transcriptional coactivators for Notch signaling, an evolutionarily conserved pathway that plays several key roles in development and in human disease. The MAML family contains MAML1, MAML2, and MAML3. More recently, MAML1 has been shown to function as a coactivator for the tumor suppressor p53, the MADS box transcription enhancer factor (MEF) 2C, and beta-catenin. In addition, MAML1 has been reported to interact with the histone acetyltransferase p300, and this interaction increases p300 activity. Furthermore, MAML1 binds to CDK8, which is a subunit of the Mediator complex. The function of MAML1 as a coactivator for diverse activators, and MAML1 interaction with broadly used coactivators, suggests that MAML1 might be a key molecule that connects various signaling pathways to regulate cellular processes in normal cells and in human disease.

The nuclear receptor steroidogenic factor-1 (SF1) is critical for development and function of steroidogenic tissues. Posttranslational modifications are known to influence the transcriptional capacity of SF1, and it was previously demonstrated that serine 203 is phosphorylated. In this paper we report that serine 203 is phosphorylated by a cyclin-dependent kinase 7 (CDK7)-mediated process. As part of the CDK-activating kinase complex, CDK7 is a component of the basal transcription factor TFIIH, and phosphorylation of SF1 as well as SF1-dependent transcription was clearly reduced in cells carrying a mutation that renders the CDK-activating kinase complex unable to interact with the TFIIH core. Coimmunoprecipitation analyses revealed that SF1 and CDK7 reside in the same complex, and kinase assays demonstrated that immunoprecipitated CDK7 and purified TFIIH phosphorylate SF1 in vitro. The CDK inhibitor roscovitine blocked phosphorylation of SF1, and an inactive form of CDK7 repressed the phosphorylation level and the transactivation capacity of SF1. Structural studies have identified phosphoinositides as potential ligands for SF1. Interestingly, we found that mutations designed to block phospholipid binding dramatically decreased the level of SF1 phosphorylation. Together our results suggest a connection between ligand occupation and phosphorylation and association with the basic transcriptional machinery, indicating an intricate regulation of SF1 transactivation.

Ligand activation of Notch leads to the release of Notch IC (the intracellular receptor domain), which translocates to the nucleus and interacts with the DNA-binding protein CSL to control expression of specific target genes. In addition to ligand-mediated activation, Notch signalling can be further modulated by interactions of Notch IC with a number of other proteins. MAML1 has previously been shown to act co-operatively with the histone acetyltransferase p300 in Notch IC-mediated transcription. In the present study we show that the N-terminal domain of MAML1 directly interacts with both p300 and histones, and the p300-MAML1 complex specifically acetylates histone H3 and H4 tails in chromatin. Furthermore, p300 acetylates MAML1 and evolutionarily conserved lysine residues in the MAML1 N-terminus are direct substrates for p300-mediated acetylation. The N-terminal domain of MAML1 contains a proline repeat motif (PXPAAPAP) that was previously shown to be present in p53 and important for the p300-p53 interaction. We show that the MAML1 proline repeat motif interacts with p300 and enhances the activity of the MAML1 N-terminus in vivo. These findings suggest that the N-terminal domain of MAML1 plays an important role in Notch-regulated transcription, by direct interactions with Notch, p300 and histones.

Transcriptional coactivators showing physical and functional interactions with PPARgamma include the protein acetyl transferase p300, the TRAP/Mediator complex that interacts with the general transcription machinery, and the highly regulated PGC-1alpha. We show that PGC-1alpha directly interacts with TRAP/Mediator, through the PPARgamma-interacting subunit TRAP220, and stimulates TRAP/Mediator-dependent function on DNA templates. Further, while ineffective by itself, PGC-1alpha stimulates p300-dependent histone acetylation and transcription on chromatin templates in response to PPARgamma. These functions are mediated by largely independent PPARgamma, p300, and TRAP220 interaction domains in PGC-1alpha, whereas p300 and TRAP220 show ligand-dependent interactions with a common region of PPARgamma. Apart from showing PGC-1alpha functions both in chromatin remodeling and in preinitiation complex formation or function (transcription), these results suggest a key role for PGC-1alpha, through concerted but dynamic interactions, in coordinating these steps.

The orphan nuclear receptor hepatocyte nuclear factor 4 (HNF-4) regulates the expression of many liver-specific genes both during development and in the adult animal. Towards understanding the molecular mechanisms by which HNF-4 functions, we have established in vitro transcription systems that faithfully recapitulate HNF-4 activity. Here we have focused on the coactivator requirements for HNF-4, especially for the multicomponent TRAP/SMCC/Mediator complex that has emerged as the central regulatory module of the transcription apparatus. Using a system that has been reconstituted from purified transcription factors, as well as one consisting of unfractionated nuclear extract from which TRAP/SMCC/Mediator has been depleted by specific antibodies, we demonstrate a strong dependence of HNF-4 function on this coactivator. Importantly, we further show a TRAP/SMCC/Mediator-dependence for HNF-4 transcriptional activation from chromatin templates. The latter involves cooperation with the histone acetyltransferase-containing coactivator p300, in accord with a synergistic mode of action of the two divergent coactivators. We also show that HNF-4 and TRAP/SMCC/Mediator can interact physically. This interaction likely involves primary HNF-4 activation function 2 (AF-2)-dependent interactions with the TRAP220 subunit of TRAP/SMCC/Mediator and secondary (AF-2-independent) interactions with TRAP170/RGR1. Finally, recruitment experiments using immobilized templates strongly suggest that the functional consequences of the physical interaction probably are manifested at a postrecruitment step in the activation pathway.