Drosophila melanogaster dHCF Interacts with both PcG and TrxG Epigenetic Regulators

Repression and activation of gene transcription involves multiprotein complexes that modify chromatin structure. The integration of these complexes at regulatory sites can be assisted by co-factors that link them to DNA-bound transcriptional regulators. In humans, one such co-factor is the herpes simplex virus host-cell factor 1 (HCF-1), which is implicated in both activation and repression of transcription. We show here that disruption of the gene encoding the Drosophila melanogaster homolog of HCF-1, dHCF, leads to a pleiotropic phenotype involving lethality, sterility, small size, apoptosis, and morphological defects. In Drosophila, repressed and activated transcriptional states of cell fate-determining genes are maintained throughout development by Polycomb Group (PcG) and Trithorax Group (TrxG) genes, respectively. dHCF mutant flies display morphological phenotypes typical of TrxG mutants and dHCF interacts genetically with both PcG and TrxG genes. Thus, dHCF inactivation enhances the mutant phenotypes of the Pc PcG as well as brm and mor TrxG genes, suggesting that dHCF possesses Enhancer of TrxG and PcG (ETP) properties. Additionally, dHCF interacts with the previously established ETP gene skd. These pleiotropic phenotypes are consistent with broad roles for dHCF in both activation and repression of transcription during fly development

A genome-wide computational approach to define microRNA-Polycomb/ trithorax gene regulatory circuits in drosophila

Characterization of gene regulatory networks is fundamental to understanding homeostatic development. This process can be simplified by analyzing relatively simple genomes such as the genome of Drosophila melanogaster. In this work we have developed a computational framework in Drosophila to explore for the presence of gene regulatory circuits between two large groups of transcriptional regulators: the epigenetic group of the Polycomb/ trithorax (PcG/trxG) proteins and the microRNAs (miRNAs). We have searched genome-wide for miRNA targets in PcG/trxG transcripts as well as for Polycomb Response Elements (PREs) in miRNA genes. Our results show that 10% of the analyzed miRNAs could be controlling PcG/trxG gene expression, while 40% of those miRNAs are putatively controlled by the selected set of PcG/trxG proteins. The integration of these analyses has resulted in the predicted existence of 3 classes of miRNA-PcG/trxG crosstalk interactions that define potential regulatory circuits. In the first class, miRNA-PcG circuits are defined by miRNAs that reciprocally crosstalk with PcG. In the second, miRNA-trxG circuits are defined by miRNAs that reciprocally crosstalk with trxG. In the third class, miRNA-PcG/ trxG shared circuits are defined by miRNAs that crosstalk with both PcG and trxG regulators. These putative regulatory circuits may uncover a novel mechanism in Drosophila for the control of PcG/trxG and miRNAs levels of expression. The computational framework developed here for Drosophila melanogaster can serve as a model case for similar analyses in other species. Moreover, our work provides, for the first time, a new and useful resource for the Drosophila community to consult prior to experimental studies investigating the epigenetic regulatory networks of miRNA-PcG/trxG mediated gene expressionWe thank Dr. Peter Freddolino (University of Michigan Medical School, USA) for kindly providing us with the Polycomb Response Element genome-wide predictor (Khabiri and Freddolino, 2019) and Keith Harshman for carefully reading the manuscript. This work was supported by PID2020-114533 GB-C21 grant from Spanish Agencia Estatal de Investigacion/Ministerio de Ciencia e Innovaci on and by institutional grants from Fundacion Areces and Banco Santande

Polycomb Controls Gliogenesis by Regulating the Transient Expression of the Gcm/Glide Fate Determinant

The Gcm/Glide transcription factor is transiently expressed and required in the Drosophila nervous system. Threshold Gcm/Glide levels control the glial versus neuronal fate choice, and its perdurance triggers excessive gliogenesis, showing that its tight and dynamic regulation ensures the proper balance between neurons and glia. Here, we present a genetic screen for potential gcm/glide interactors and identify genes encoding chromatin factors of the Trithorax and of the Polycomb groups. These proteins maintain the heritable epigenetic state, among others, of HOX genes throughout development, but their regulatory role on transiently expressed genes remains elusive. Here we show that Polycomb negatively affects Gcm/Glide autoregulation, a positive feedback loop that allows timely accumulation of Gcm/Glide threshold levels. Such temporal fine-tuning of gene expression tightly controls gliogenesis. This work performed at the levels of individual cells reveals an undescribed mode of Polycomb action in the modulation of transiently expressed fate determinants and hence in the acquisition of specific cell identity in the nervous system. © 2012 Popkova et al.Fondation pour la Recherche Médicale and by Centre Européen de Recherche en Biologie et en Médecine; Association pour la Recherche sur le Cancer; Institut National de la Santé et de la Recherche Médicale; Centre National de la Recherche Scientifique; Université de Strasbourg; Hôpital de Strasbourg; Institut National du Cancer; the Agence Nationale de la Recherche; Alma Mater Studiorum; Università di Bologna; European Research Council (ERC-2008-AdG No 232947); Institut National de la Santé et de la Recherche Médicale; Centre National de la Recherche Scientifique; European Network of Excellence EpiGeneSys; Fundacion Mutua Madrileña (FMM-2006) and Ministerio de Ciencia y Tecnología (BFU-2008-5404)Peer Reviewe

dRYBP counteracts chromatin-dependent activation and repression of transcription

Chromatin dependent activation and repression of transcription is regulated by the histone modifying enzymatic activities of the trithorax (trxG) and Polycomb (PcG) proteins. To investigate the mechanisms underlying their mutual antagonistic activities we analyzed the function of Drosophila dRYBP, a conserved PcG- and trxG-associated protein. We show that dRYBP is itself ubiquitylated and binds ubiquitylated proteins. Additionally we show that dRYBP maintains H2A monoubiquitylation, H3K4 monomethylation and H3K36 dimethylation levels and does not affect H3K27 trimethylation levels. Further we show that dRYBP interacts with the repressive SCE and dKDM2 proteins as well as the activating dBRE1 protein. Analysis of homeotic phenotypes and post-translationally modified histones levels show that dRYBP antagonizes dKDM2 and dBRE1 functions by respectively preventing H3K36me2 demethylation and H2B monoubiquitylation. Interestingly, our results show that inactivation of dBRE1 produces trithorax-like related homeotic transformations, suggesting that dBRE1 functions in the regulation of homeotic genes expression. Our findings indicate that dRYBP regulates morphogenesis by counteracting transcriptional repression and activation. Thus, they suggest that dRYBP may participate in the epigenetic plasticity important during normal and pathological development

The Polyhomeotic protein induces hyperplastic tissue overgrowth through the activation of the JAK/STAT pathway.

Epigenetic mechanisms controlling cellular proliferation are essential to animal development. Moreover, altered levels of expression of the epigenetic regulator proteins are associated with the development and progression of human diseases like cancer. We have studied the effects of high levels of Polyhomeotic (PH) protein, a member of the Polycomb Group (PcG), during the proliferation of the imaginal discs in Drosophila. Overexpression of PH protein causes induction of proliferation, accompanied with induction of JNK-dependent apoptosis. As a result, massive hyperplastic overgrowth is produced and the corresponding differentiated tissues show phenotypes related with mis-regulation of homeotic gene expression. We have found that high levels of PH upregulate the JAK/STAT pathway through the de-repression of Unpaired (UPD), the extracellular ligand of the Drosophila JAK/STAT signalling cascade. Moreover, inactivation of the JAK/STAT pathway in the presence of a large amount of PH protein greatly reduces the tissue overgrowth, demonstrating a functional role of JAK/STAT in PH-induced hyperplasia. Finally, we have observed that decapentaplegic and d-myc, two growth genes and putative targets of the JAK/STAT pathway, are also overexpressed in the PH-induced tumors. We propose that during normal development, the PcG proteins act to maintain inactive the JAK/STAT pathway. Upon cellular stress, changes in the levels of PcG proteins expression are induced and JAK/STAT is activated leading to tumor development. Our results show a functional relationship between the PcG gene expression and the JAK/STAT pathway, both of which are found to be perturbed in tumorigenesis.This work was supported by grants from the Dirección General de Investigación (BFU 2008- 01154), Fundación Investigación Médica Mutua Madrileña (FMM-2006), the Consolider Ingenio 2010 Program of the Ministerio de Ciencia e Innovación (CSD 2007-00008) to A.B. and by an institutional grant to the Centro de Biología Molecular Severo Ochoa from the Fundación Ramón Areces.Peer reviewe

Identification of two forms of the maltose transport system in Saccharomyces cerevisiae and their regulation by catabolite inactivation

The maltose transport system of Saccharomyces cerevisiae exists in two forms with Km values of approx. 4 mM and 70 mM, respectively. The Vmax of the high-Km form is about 4-fold greater than the Vmax of the low one. A rapid and irreversible inactivation of both forms is detected on protein synthesis impairment. This inactivation is stimulated by the catabolism of fermentable sugars and prevented during ethanol catabolism. It is concluded that both forms of the maltose transport system are regulated by catabolite inactivation. © 1985.This work was supported by Comisión Asesora para la Investigación Científica y Tecnica. A.B. had a fellowship of Gobierno Vasco, Departamento de Universidades e Investigación.Peer Reviewe

Identification of two forms of the maltose transport system in Saccharomyces cerevisiae and their regulation by catabolite inactivation

The maltose transport system of Saccharomyces cerevisiae exists in two forms with Km values of approx. 4 mM and 70 mM, respectively. The Vmax of the high-Km form is about 4-fold greater than the Vmax of the low one. A rapid and irreversible inactivation of both forms is detected on protein synthesis impairment. This inactivation is stimulated by the catabolism of fermentable sugars and prevented during ethanol catabolism. It is concluded that both forms of the maltose transport system are regulated by catabolite inactivation. © 1985.This work was supported by Comisión Asesora para la Investigación Científica y Tecnica. A.B. had a fellowship of Gobierno Vasco, Departamento de Universidades e Investigación.Peer Reviewe

Efecto Pasteur en saccharomyces cerevisiae: inactivación de los sistemas de transporte de azúcares

Tesis Doctoral inédita leida en la Universidad Autonoma de Madrid, Facultad de Ciencias. Fecha de lectura 14-03-198

Genetic structure of the abd-A gene of Drosophila

We report the embryonic and adult phenotypes of a number of mutations of the abd-A gene of the bithorax complex. Some of them result in loss of abd-A function in the whole abd-A domain and are usually lethal. These probably eliminate or inactivate abd-A protein products. Other mutations affect only part of the abd-A domain. These are viable, appear to map outside the abd-A transcription unit, and presumably alter the normal spatial regulation of abd-A products. We propose a model of abd-A structure based on a protein-coding region and two cis-regulatory regions. Regulatory region 1, 3' to the transcription unit, contains positive and negative regulatory elements. Regulatory region 2, 5' to the transcription unit, establishes the correct level of abd-A activity in the abdominal metameresAgenda Nacional de Evaluación and the Ramón Areces FoundationPeer Reviewe

Molécula de ADN con actividad aisladora de efectos de posición cromosomales en procesos de transferencia génica en células animales

Filing Date: 2002-05-10.-- Priority Data ES P200101133 (2001-05-18).[EN] The invention relates to a DNA molecule or a fragment of said DNA molecule obtained from the LCR (Locus Control Region) sequence of the mouse tyrosinase gene. Said sequence has insulating activity against chromosomal position effects in gene transfer processes in animal cells. The DNA molecule can be used to introduce transgenes and to reduce the variability of the transgene expression in animal cells.[ES] Molécula de ADN o un fragmento de la misma obtenida a partir de la secuencia LCR (Locus Control Region) del gen de la tirosinasa de ratón. Dicha secuencia tiene actividad aisladora de efectos de posición cromosomales en procesos de transferencia génica en células de animales. La molécula de ADN puede utilizarse para introducir transgenes y reducir la variabilidad de la expresión de transgenes en células de animales