Yin Yang 1 extends the Myc-related transcription factors network in embryonic stem cells

The Yin Yang 1 (YY1) transcription factor is a master regulator of development, essential for early embryogenesis and adult tissues formation. YY1 is the mammalian orthologue of Pleiohomeotic, one of the transcription factors that binds Polycomb DNA response elements in Drosophila melanogaster and mediates Polycomb group proteins (PcG) recruitment to DNA. Despite several publications pointing at YY1 having a similar role in mammalians, others showed features of YY1 that are not compatible with PcG functions. Here, we show that, in mouse Embryonic Stem (ES) cells, YY1 has genome-wide PcG-independent activities while it is still stably associated with the INO80 chromatin-remodeling complex, as well as with novel RNA helicase activities. YY1 binds chromatin in close proximity of the transcription start site of highly expressed genes. Loss of YY1 functions preferentially led to a down-regulation of target genes expression, as well as to an up-regulation of several small non-coding RNAs, suggesting a role for YY1 in regulating small RNA biogenesis. Finally, we found that YY1 is a novel player of Myc-related transcription factors and that its coordinated binding at promoters potentiates gene expression, proposing YY1 as an active component of the Myc transcription network that links ES to cancer cells

Visible light 3D printing with epoxidized vegetable oils

Stereolithography is a 3D printing technique in which a liquid monomer is photopolymerized to produce a solid object. The most widely used materials usually belong to the family of acrylate monomers, and photopolymerization occurs through a radical pathway. Photoinitiators can absorb UV or (less often) visible light, producing radicals for direct decomposition or hydrogen abstraction. Due to the toxicity of acrylates, vegetable oil-derived monomers were used in this study. In fact, vegetable oils contain unsaturations, and thus, they can be exploited as monomers. In particular, linseed oil, tung oil or edible oils (soybean, sunflower or corn) could be good candidates as raw materials. Unfortunately, the photoinduced radical polymerization of these oils either does not occur or is too slow for 3D printing applications. For this reason, the oils were modified as epoxides. Epoxides are monomers that are more reactive than natural oils, and they can be polymerized via a cationic mechanism. The aim of this work was to exploit visible light generated by a common digital projector (like those used in classrooms) as a light source. Since the tested photoacid generators working under visible light are ineffective for the polymerization of epoxidized oils, a multi-component photo-initiating mixture was used

PRMT1 Is Recruited via DNA-PK to Chromatin Where It Sustains the Senescence-Associated Secretory Phenotype in Response to Cisplatin

Summary: Protein arginine methyltransferase 1 (PRMT1) is overexpressed in various human cancers and linked to poor response to chemotherapy. Various PRMT1 inhibitors are currently under development; yet, we do not fully understand the mechanisms underpinning PRMT1 involvement in tumorigenesis and chemoresistance. Using mass spectrometry-based proteomics, we identified PRMT1 as regulator of arginine methylation in ovarian cancer cells treated with cisplatin. We showed that DNA-dependent protein kinase (DNA-PK) binds to and phosphorylates PRMT1 in response to cisplatin, inducing its chromatin recruitment and redirecting its enzymatic activity toward Arg3 of histone H4 (H4R3). On chromatin, the DNA-PK/PRMT1 axis induces senescence-associated secretory phenotype through H4R3me2a deposition at pro-inflammatory gene promoters. Finally, PRMT1 inhibition reduces the clonogenic growth of cancer cells exposed to low doses of cisplatin, sensitizing them to apoptosis. While unravelling the role of PRMT1 in response to genotoxic agents, our findings indicate the possibility of targeting PRMT1 to overcome chemoresistance in cancer. : Protein arginine methyltransferase 1 (PRMT1) overexpression is linked to cancer chemoresistance, but the mechanism is still unclear. Musiani et al. show that, upon cisplatin, PRMT1 is recruited by DNA-dependent protein kinase (DNA-PK) to chromatin, where it sustains the transcription of genes involved in the senescence-associated secretory phenotype (SASP), thus protecting cells from drug-induced apoptosis. Keywords: arginine methylation, MS-based proteomics, replication stress response, PRMT1, SASP, transcription, cisplatin, epigenetic drugs, DNA-P

Multi-label transcriptional classification of colorectal cancer reflects tumor cell population heterogeneity

Background: Transcriptional classification has been used to stratify colorectal cancer (CRC) into molecular subtypes with distinct biological and clinical features. However, it is not clear whether such subtypes represent discrete, mutually exclusive entities or molecular/phenotypic states with potential overlap. Therefore, we focused on the CRC Intrinsic Subtype (CRIS) classifier and evaluated whether assigning multiple CRIS subtypes to the same sample provides additional clinically and biologically relevant information. Methods: A multi-label version of the CRIS classifier (multiCRIS) was applied to newly generated RNA-seq profiles from 606 CRC patient-derived xenografts (PDXs), together with human CRC bulk and single-cell RNA-seq datasets. Biological and clinical associations of single- and multi-label CRIS were compared. Finally, a machine learning-based multi-label CRIS predictor (ML2CRIS) was developed for single-sample classification. Results: Surprisingly, about half of the CRC cases could be significantly assigned to more than one CRIS subtype. Single-cell RNA-seq analysis revealed that multiple CRIS membership can be a consequence of the concomitant presence of cells of different CRIS class or, less frequently, of cells with hybrid phenotype. Multi-label assignments were found to improve prediction of CRC prognosis and response to treatment. Finally, the ML2CRIS classifier was validated for retaining the same biological and clinical associations also in the context of single-sample classification. Conclusions: These results show that CRIS subtypes retain their biological and clinical features even when concomitantly assigned to the same CRC sample. This approach could be potentially extended to other cancer types and classification systems

Characterization of an antagonistic switch between histone H3 lysine 27 methylation and acetylation in the transcriptional regulation of Polycomb group target genes

Polycomb group (PcG) proteins are transcriptional repressors, which regulate proliferation and cell fate decisions during development, and their deregulated expression is a frequent event in human tumours. The Polycomb repressive complex 2 (PRC2) catalyzes trimethylation (me3) of histone H3 lysine 27 (K27), and it is believed that this activity mediates transcriptional repression. Despite the recent progress in understanding PcG function, the molecular mechanisms by which the PcG proteins repress transcription, as well as the mechanisms that lead to the activation of PcG target genes are poorly understood. To gain insight into these mechanisms, we have determined the global changes in histone modifications in embryonic stem (ES) cells lacking the PcG protein Suz12 that is essential for PRC2 activity. We show that loss of PRC2 activity results in a global increase in H3K27 acetylation. The methylation to acetylation switch correlates with the transcriptional activation of PcG target genes, both during ES cell differentiation and in MLL-AF9-transduced hematopoietic stem cells. Moreover, we provide evidence that the acetylation of H3K27 is catalyzed by the acetyltransferases p300 and CBP. Based on these data, we propose that the PcG proteins in part repress transcription by preventing the binding of acetyltransferases to PcG target genes

The Polycomb Repressive Complex 2 Is a Potential Target of SUMO Modifications

The Polycomb Repressive Complex 2 (PRC2) functions as a transcriptional repressor through a mechanism that involves methylation of Histone H3 at lysine 27. The PRC2 complex activity is essential for cellular proliferation, development, and cell fate decisions. PRC2 target genes include important regulators of development and proliferation as well as tumor suppressor genes. Consistent with this, the activity of several Polycomb group (PcG) proteins is deregulated in human cancer suggesting an important role for PcGs in tumor development. Whereas the downstream functions of PcGs are well characterized, the mechanisms of their recruitment to target genes and the regulation of their activity are not fully understood.Here we show that the two PRC2 components SUZ12 and EZH2 are sumoylated in vitro and in vivo. Among several putative sumoylation sites we have mapped the major site of SUZ12 sumoylation. Furthermore, we show that SUZ12 interacts with the E2-conjugating enzyme UBC9 both in vitro and in vivo and that mutation of the SUZ12 sumoylation site does not abolish this binding. Finally, we provide evidence that the E3-ligase PIASXbeta interacts and enhances the sumoylation of SUZ12 in vivo suggesting that PIASXbeta could function as an E3-ligase for SUZ12.Taken together, our data identify sumoylation as a novel post-translational modification of components of the PRC2 complex, which could suggest a potential new mechanism to modulate PRC2 repressive activity. Further work aimed to identify the physiological conditions for these modifications will be required to understand the role of SUZ12 and EZH2 sumoylation in PcG-mediated epigenetic regulation of transcription

Equipamento de Baixo Custo com Tecnologia 100% Nacional para Ensaio de Fadiga por Flexão Rotativa

Componentes metálicos com funções estruturais devem manter-se íntegros durante toda sua vida útil. Para atingir tais objetivos, é necessário efetuar Avaliações de Integridade Estrutural (AIE) e Previsões de Vida Residual (PVR) periodicamente. O estudo das propriedades dos materiais é fundamental para o desenvolvimento de novos componentes, sendo que uma importante propriedade é a resistência à fadiga, a qual prevê a vida útil do material em balanço. Para ser definida a vida em fadiga, o material deve ser submetido a ensaios cíclicos de tensão alternada, onde o ciclo de tensão máxima e mínima são iguais em magnitude. O valor de ciclos de tensão suportados pelo corpo de prova são representados por N, sendo contabilizado pelo equipamento utilizado no ensaio. O limite de resistência do material a fadiga σn representa o valor máximo suportado por um material em um determinado número de ciclos antes de sua ruptura. A forma como os resultados são apresentados se dá pela curva σ-N, (WÖHLER, 1852 - 1869). Neste trabalho, foi desenvolvido equipamento para ensaio de fadiga por flexão rotativa e sua validação por meio de ensaios em corpos de prova confeccionados em aço AISI 1020 conforme a norma ASTM E 606, após a finalização dos ensaios foi levantada curva σ-N. O desenvolvimento do equipamento e os ensaios foram realizados no LABEMM (Laboratório de Ensaios Mecânicos e Metalúrgicos) localizado no IFC Luzerna. Os resultados obtidos pelo equipamento desenvolvido com recursos próprios apresentam curvas σ-N similares à literatura, e posteriormente será utilizado para o desenvolvimento de pesquisas

Glucocorticoid pharmacogenetics in pediatric idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome represents the most common type of primary glomerular disease in children: glucocorticoids (GCs) are the first-line therapy, even if considerable interindividual differences in thepir efficacy and side effects have been reported. Immunosuppressive and anti-inflammatory effects of these drugs are mainly due to the GC-mediated transcription regulation of pro- and anti-inflammatory genes. This mechanism of action is the result of a complex multistep pathway that involves the glucocorticoid receptor and several other proteins, encoded by polymorphic genes. Aim of this review is to highlight the current knowledge on genetic variants that could affect GC response, particularly focusing on children with idiopathic nephrotic syndrome

Polycomb proteins control proliferation and transformation independently of cell cycle checkpoints by regulating DNA replication

The ability of PRC1 and PRC2 to promote proliferation is a main feature that links polycomb (PcG) activity to cancer. PcGs silence the expression of the tumour suppressor locus Ink4a/Arf, whose products positively regulate pRb and p53 functions. Enhanced PcG activity is a frequent feature of human tumours, and PcG inhibition has been proposed as a strategy for cancer treatment. However, the recurrent inactivation of pRb/p53 responses in human cancers raises a question regarding the ability of PcG proteins to affect cellular proliferation independently from this checkpoint. Here we demonstrate that PRCs regulate cellular proliferation and transformation independently of the Ink4a/Arf-pRb-p53 pathway. We provide evidence that PRCs localize at replication forks, and that loss of their function directly affects the progression and symmetry of DNA replication forks. Thus, we have identified a novel activity by which PcGs can regulate cell proliferation independently of major cell cycle restriction checkpoints. \ua92014 Macmillan Publishers Limited. All rights reserved

Antagonism between DNA and H3K27 Methylation at the Imprinted Rasgrf1 Locus

At the imprinted Rasgrf1 locus in mouse, a cis-acting sequence controls DNA methylation at a differentially methylated domain (DMD). While characterizing epigenetic marks over the DMD, we observed that DNA and H3K27 trimethylation are mutually exclusive, with DNA and H3K27 methylation limited to the paternal and maternal sequences, respectively. The mutual exclusion arises because one mark prevents placement of the other. We demonstrated this in five ways: using 5-azacytidine treatments and mutations at the endogenous locus that disrupt DNA methylation; using a transgenic model in which the maternal DMD inappropriately acquired DNA methylation; and by analyzing materials from cells and embryos lacking SUZ12 and YY1. SUZ12 is part of the PRC2 complex, which is needed for placing H3K27me3, and YY1 recruits PRC2 to sites of action. Results from each experimental system consistently demonstrated antagonism between H3K27me3 and DNA methylation. When DNA methylation was lost, H3K27me3 encroached into sites where it had not been before; inappropriate acquisition of DNA methylation excluded normal placement of H3K27me3, and loss of factors needed for H3K27 methylation enabled DNA methylation to appear where it had been excluded. These data reveal the previously unknown antagonism between H3K27 and DNA methylation and identify a means by which epigenetic states may change during disease and development