Research Interests:
I Jornada de Cromatina i Epigenetica Organitzada per la Seccio de Biologia Molecular de la Societat Catalana de Biologia. Institut d'Estudis Catalans, 5 de marc 2010, Barcelona
Research Interests:
Research Interests:
Research Interests:
HIV-1 strains with a syncytium-inducing phenotype that use CXCR4 (X4 strains) have been associated with faster disease progression and AIDS. Antiviral agents designed to block CXCR4 may prevent the emergence of X4 HIV strains but... more
HIV-1 strains with a syncytium-inducing phenotype that use CXCR4 (X4 strains) have been associated with faster disease progression and AIDS. Antiviral agents designed to block CXCR4 may prevent the emergence of X4 HIV strains but resistant strains that maintain the X4 phenotype can be raised by sequential passage in cell cultures. We have demonstrated that a laboratory adapted strain (NL4-3) and a cloned clinical isolate (CI-1) of HIV-1 cultured in the presence of the CXCR4 antagonist, AMD3100, became resistant to the compound without a change in co-receptor use. These strains became resistant through divergence with respect to the wild-type virus. Conversely, a clinical isolate made resistant to AMD3100 switched co-receptor use from X4 to R5 through a change in diversity from the original virus population. When dual infection competition/heteroduplex tracking assays were performed, all AMD3100-resistant strains, regardless of co-receptor use showed a significantly diminished fitnes...
Research Interests:
Research Interests:
Id proteins are dominant-negative regulators within the HLH family of proteins. In embryonic stem cells (ESCs), Id1 and Id3 maintain the pluripotent state by preventing neural differentiation. The Id1-interacting protein Zrf1 plays a... more
Id proteins are dominant-negative regulators within the HLH family of proteins. In embryonic stem cells (ESCs), Id1 and Id3 maintain the pluripotent state by preventing neural differentiation. The Id1-interacting protein Zrf1 plays a crucial role as a chromatin-bound factor in specification of the neural fate from ESCs. Here, we show that Id1 blocks Zrf1 recruitment to chromatin, thus preventing the activation of neural genes in ESCs. Upon differentiation, Id1 expression decreases thus inducing Zrf1 binding to neural genes. Importantly, depletion of Zrf1 rescues the expression of Polycomb targets involved in neural specification which are up-regulated in Id1 knock-out ESCs. We therefore identified Zrf1 as transcriptional regulator of neural fate downstream of Id1 in ESCs.
Research Interests: Biology, Cell Biology, Medicine, Neural Development, Neural stem cell, and 12 moreCell Differentiation, Humans, Mice, Animals, Embryonic Stem Cell, Embryonic Stem Cells, Neurons, Chromatin, Chromatin Immunoprecipitation, DNA binding proteins, Biochemistry and cell biology, and Polycomb group proteins
Research Interests: Biology, Medicine, Gene Silencing, Western blotting, Biological Sciences, and 12 moreCell line, Animals, DNA methylation, Transcription Factor, Immunoprecipitation, Rats, Base Sequence, Cell Cycle Proteins, Methyltransferase, Corepressor, reverse transcriptase polymerase chain reaction, and Medical and Health Sciences
Research Interests: Biology, Leukemia, Cancer Research, Epigenetics, Apoptosis, and 15 moreMedicine, Acute Myeloid Leukemia, Cell Differentiation, Humans, Mice, Animals, Oncogene, Immunoprecipitation, Clinical Sciences, Disease Progression, Regulator, Cell Proliferation, DNA binding proteins, Antineoplastic Agents, and Cell Growth
Research Interests:
Phf19, a Polycomb subunit, controls hematopoietic stem cells identity and differentiation.
Research Interests:
Genome organization plays a pivotal role in transcription, but how transcription factors (TFs) rewire the structure of the genome to initiate and maintain the programs that lead to oncogenic transformation remains poorly understood. Acute... more
Genome organization plays a pivotal role in transcription, but how transcription factors (TFs) rewire the structure of the genome to initiate and maintain the programs that lead to oncogenic transformation remains poorly understood. Acute promyelocytic leukemia (APL) is a fatal subtype of leukemia driven by a chromosomal translocation between the promyelocytic leukemia (PML) and retinoic acid receptor α (RARα) genes. We used primary hematopoietic stem and progenitor cells (HSPCs) and leukemic blasts that express the fusion protein PML-RARα as a paradigm to temporally dissect the dynamic changes in the epigenome, transcriptome, and genome architecture induced during oncogenic transformation. We found that PML-RARα initiates a continuum of topologic alterations, including switches from A to B compartments, transcriptional repression, loss of active histone marks, and gain of repressive histone marks. Our multiomics-integrated analysis identifies Klf4 as an early down-regulated gene in...
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Human immunodeficiency virus type 1 (HIV-1) resistance to antiretroviral drugs is the main cause of patient treatment failure. Despite the problems associated with interpretation of HIV-1 resistance testing, resistance monitoring should... more
Human immunodeficiency virus type 1 (HIV-1) resistance to antiretroviral drugs is the main cause of patient treatment failure. Despite the problems associated with interpretation of HIV-1 resistance testing, resistance monitoring should help in the rational design of initial or rescue antiretroviral therapies. It has previously been shown that the activity of the HIV-1 protease can be monitored by using a bacteriophage lambda-based genetic assay. This genetic screening system is based on the bacteriophage lambda regulatory circuit in which the viral repressor c I is specifically cleaved to initiate the lysogenic to lytic switch. We have adapted this simple lambda-based genetic assay for the analysis of the activities and phenotypes of different HIV-1 proteases. Lambda phages that encode HIV-1 proteases either from laboratory strains (strain HXB2) or from clinical samples are inhibited in a dose-dependent manner by the HIV-1 protease inhibitors indinavir, ritonavir, saquinavir, and n...
Research Interests: Microbiology, Medical Microbiology, Biology, Medicine, Humans, and 15 moreMutagenesis, Protease, HIV protease, Genetic Screening, Human immunodeficiency virus, Protease Inhibitors, Antimicrobial agents, Amino Acid Sequence, Proteases, Bacteriophage, Lytic Cycle, Molecular Sequence Data, ritonavir, Pharmacology and pharmaceutical sciences, and indinavir
The cellular plasticity of pluripotent stem cells is thought to be sustained by genomic regions that display both active and repressive chromatin properties. These regions exhibit low levels of gene expression, yet the mechanisms... more
The cellular plasticity of pluripotent stem cells is thought to be sustained by genomic regions that display both active and repressive chromatin properties. These regions exhibit low levels of gene expression, yet the mechanisms controlling these levels remain unknown. Here, we describe Elongin BC as a binding factor at the promoters of bivalent sites. Biochemical and genome-wide analyses show that Elongin BC is associated with Polycomb Repressive Complex 2 (PRC2) in pluripotent stem cells. Elongin BC is recruited to chromatin by the PRC2-associated factor EPOP (Elongin BC and Polycomb Repressive Complex 2 Associated Protein, also termed C17orf96, esPRC2p48, E130012A19Rik), a protein expressed in the inner cell mass of the mouse blastocyst. Both EPOP and Elongin BC are required to maintain low levels of expression at PRC2 genomic targets. Our results indicate that keeping the balance between activating and repressive cues is a more general feature of chromatin in pluripotent stem c...
Research Interests: Biology, Cell Biology, Stem Cell, Transcription Factors, Medicine, and 12 moreCell and Molecular Biology, Biological Sciences, Cell Differentiation, Mice, Animals, Chromatin, Histones, Protein Binding, Polycomb group proteins, Pluripotent Stem Cells, embryo implantation, and Medical and Health Sciences
II Jornada de Cromatina i Epigenetica Organitzada per la Seccio de Biologia Molecular de la Societat Catalana de Biologia. Institut d'Estudis Catalans; 4 de marc 2011 Barcelona
Research Interests:
Research Interests:
The human immunodeficiency virus (HIV) inhibitor AR177 (T30177, Zintevir) has been identified as a potent inhibitor of HIV integrase in vitro. The compound is currently the subject of clinical phase I/II trials. However, the primary... more
The human immunodeficiency virus (HIV) inhibitor AR177 (T30177, Zintevir) has been identified as a potent inhibitor of HIV integrase in vitro. The compound is currently the subject of clinical phase I/II trials. However, the primary target for the mechanism of action in vivo has not been identified unequivocally. We have found that AR177 inhibits syncytium formation between MOLT-4 cells and HUT-78 cells persistently infected with the HIV-1IIIB or NL4-3 strain, at a 50% effective concentration of 3 microg/ml, roughly 3-fold higher than the concentration required to inhibit HIV replication. Furthermore, flow cytometric analysis has shown that AR177 at 25 microg/ml interferes with the binding of the monoclonal antibody 9284 (directed to the V3 loop of gp120) on HIVIIIB-infected HUT-78 cells, pointing to inhibition of virus binding or virus fusion as the mechanism of action of AR177. To precisely characterize the site/target of intervention by AR177, we have selected HIV-1 (NL4-3) strains resistant to AR177. The binding of the AR177-resistant strain, unlike the parental HIV-1 NL4-3 strain, could not be inhibited by AR177. The resistant phenotype was associated with the emergence of mutations in the gp120 molecule. DNA sequence analysis revealed the presence of the K148E, Q278H, K290Q, and F391I mutations and a deletion of 5 amino acids (FNSTW) at positions 364-368 in the V4 region of the resistant strain but not of the wild-type HIV strain. Selection of resistant strains, although it takes a relatively long time to develop, may also select for strains with lower replicative capacity. No mutations were found in the integrase enzyme gene. Our data argue against HIV integrase being the primary target for the mechanism of anti-HIV action of AR177.
Research Interests:
The emergence of X4 human immunodeficiency virus type 1 (HIV-1) strains in HIV-1-infected individuals has been associated with CD4(+) T-cell depletion, HIV-mediated CD8(+) cell apoptosis, and an impaired humoral response. The bicyclam... more
The emergence of X4 human immunodeficiency virus type 1 (HIV-1) strains in HIV-1-infected individuals has been associated with CD4(+) T-cell depletion, HIV-mediated CD8(+) cell apoptosis, and an impaired humoral response. The bicyclam AMD3100, a selective antagonist of CXCR4, selected for the outgrowth of R5 virus after cultivation of mixtures of the laboratory-adapted R5 (BaL) and X4 (NL4-3) HIV strains in the presence of the compound. The addition of AMD3100 to peripheral blood mononuclear cells infected with X4 or R5X4 clinical HIV isolates displaying the syncytium-inducing phenotype resulted in a complete suppression of X4 variants and a concomitant genotypic change in the V2 and V3 loops of the envelope gp120 glycoprotein. The recovered viruses corresponded genotypically and phenotypically to R5 variants in that they could no longer use CXCR4 as coreceptor or induce syncytium formation in MT-2 cells. Furthermore, the phenotype and genotype of a cloned R5 HIV-1 virus converted t...
Research Interests:
Infection by human immunodeficiency virus type 1 (HIV-1) has been associated with increased cell death of both infected and bystander cells. The envelope glycoprotein complex appears to play an active role in HIV-induced death of... more
Infection by human immunodeficiency virus type 1 (HIV-1) has been associated with increased cell death of both infected and bystander cells. The envelope glycoprotein complex appears to play an active role in HIV-induced death of bystander cells. We quantified cell-to-cell fusion, single cell death and membrane lipid mixing in cocultures of effector, HIV-1 envelope-expressing cells with peripheral blood mononuclear cells or purified CD4 T lymphocytes from HIV-negative donors, in the presence or the absence of the fusion inhibitor enfuvirtide (T-20, pentafuside, Fuzeon). T-20, which blocks gp41-dependent virus-cell fusion, showed a complete and dose-dependent inhibition of syncytium formation in cocultures of envelope-expressing cells with uninfected cells. Similarly, T-20 totally abrogated death of single bystander CD4 T cells with an IC50 of 0.04 microg/ml. Membrane lipid mixing, as a measure of interaction between envelope-expressing cells and CD4 cells, was also dose-dependently ...
Research Interests:
Human UTX, a member of the Jumonji C family of proteins, associates with mixed-lineage leukemia 3/4 complexes. Stimulation with retinoic acid leads to the recruitment of UTX-containing complexes to HOX genes, which results in... more
Human UTX, a member of the Jumonji C family of proteins, associates with mixed-lineage leukemia 3/4 complexes. Stimulation with retinoic acid leads to the recruitment of UTX-containing complexes to HOX genes, which results in demethylation of histone H3 lysine 27 and concomitant methylation of histone H3 lysine 4. Here, we show that UTX interacts with the retinoic acid receptor α (RARα) and that this interaction is essential for proper differentiation of leukemic U937 cells in response to retinoic acid. UTX occupies the promoters of several RAR target genes and regulates their transcriptional output by modulating ASH2L complex recruitment. Overexpression of UTX in promyelocytic NB4 cells results in enhanced cellular differentiation upon retinoic acid treatment. Our results show that UTX is important for RAR-mediated transcription and provide insight into the critical role of cross talk between histone H3 lysine 4 methylation and histone H3 lysine 27 demethylation during cellular differentiation.
Research Interests:
The transcriptional factor Snail1 is a repressor of E-cadherin (CDH1) gene expression essential for triggering epithelial-mesenchymal transition. Snail1 represses CDH1, directly binding its promoter and inducing the synthesis of the Zeb1... more
The transcriptional factor Snail1 is a repressor of E-cadherin (CDH1) gene expression essential for triggering epithelial-mesenchymal transition. Snail1 represses CDH1, directly binding its promoter and inducing the synthesis of the Zeb1 repressor. In this article, we show that repression of CDH1 by Snail1, but not by Zeb1, is dependent on the activity of Polycomb repressive complex 2 (PRC2). Embryonic stem (ES) cells null for Suz12, one of the components of PRC2, show higher levels of Cdh1 mRNA than control ES cells. In tumor cells, interference of PRC2 activity prevents the ability of Snail1 to downregulate CDH1 and partially derepresses CDH1. Chromatin immunoprecipitation assays demonstrated that Snail1 increases the binding of Suz12 to the CDH1 promoter and the trimethylation of lysine 27 in histone H3. Moreover, Snail1 interacts with Suz12 and Ezh2, as shown by coimmunoprecipitation experiments. In conclusion, these results demonstrate that Snail1 recruits PRC2 to the CDH1 prom...
Research Interests:
Research Interests:
Research Interests:
Overproduction of beta-chemokines and genetic variations in chemokine receptors have been correlated with protection against infection by HIV-1 or slow progression to AIDS in infected individuals. The protective role of chemokines and... more
Overproduction of beta-chemokines and genetic variations in chemokine receptors have been correlated with protection against infection by HIV-1 or slow progression to AIDS in infected individuals. The protective role of chemokines and their receptors was evaluated in a group of seven uninfected (seronegative) hemophiliacs transfused with hemoderivatives presumably contaminated with HIV-1. This group was compared to a group of seven infected (seropositive) hemophiliacs and a group of healthy donors (controls). The CD4+ cell count, intracellular cytokine levels, beta-chemokine levels in plasma, beta-chemokine production by PBMNCs, and expression of chemokine receptors CCR5 and CXCR4 in CD4+ cells were evaluated. The occurrence of protective genotypes in CCR5, CCR2b, and SDF-1 (stromal cell-derived factor 1) genes and susceptibility to infection by HIV-1 were also studied. Significant differences in the production and plasma levels of beta-chemokines among the three groups were not detected. Lower IL-2 and IFN-gamma production was observed in the uninfected exposed hemophiliacs than in the controls. Genetic analysis of CCR5, CCR2b, and SDF-1 showed several polymorphisms associated with resistance in some HIV-exposed uninfected hemophiliacs. However, these genetic features cannot explain the protection of all exposed hemophiliacs. In fact, only one patient, carrying two copies of CCR5 from which 32 bp was deleted, showed low CCR5 expression and low susceptibility to infection by a CCR5-using HIV-1 strain. In contrast, PBMNCs from all other individuals supported infection in vitro by both CCR5- and CXCR4-using HIV-1 strains. It is not possible to assign to beta-chemo-kines and polymorphisms in chemokine receptors a central role in preventing HIV-1 infection. Natural protection against HIV-1 infection is likely to be due to a multiplicity of factors.
Research Interests:
Research Interests:
Research Interests: Leukemia, Transcription Factors, Multidisciplinary, Gene Silencing, Western blotting, and 16 moreRNA interference, Hematopoietic Stem Cells, Cell line, Cell Differentiation, Humans, HIstone Deacetylase, Plasmids, Immunoprecipitation, Chromatin, HeLa cells, Chromatin Immunoprecipitation, Protein Binding, DNA binding proteins, Acute Promyelocytic Leukemia, Oligonucleotides, and Histone deacetylases
Estrogen receptor alpha (ERalpha) and E-cadherin are primary markers of luminal epithelial breast cancer cells with E-cadherin being a main caretaker of the epithelial phenotype. E-cadherin repression is needed for cancer cells to acquire... more
Estrogen receptor alpha (ERalpha) and E-cadherin are primary markers of luminal epithelial breast cancer cells with E-cadherin being a main caretaker of the epithelial phenotype. E-cadherin repression is needed for cancer cells to acquire motile and invasive properties, and it is known that in ER-positive breast cancer cells, estrogen down-regulate E-cadherin gene transcription. We report here that ERalpha is bound to the E-cadherin promoter in both the presence and the complete absence of estrogen, suggesting an unexpected role for unliganded ERalpha in E-cadherin transcription. Indeed, our data reveal that activation by unliganded ERalpha and repression by estrogen-activated ERalpha require direct binding to a half-estrogen response element within the E-cadherin promoter and exchange from associated coactivators to corepressors. Therefore, these results suggest a pivotal role for unliganded ERalpha in controlling a fundamental caretaker of the epithelial phenotype in breast cancer cells. Here, we show that ERalpha-positive breast cancer T47D cells transduced with the sfRON kinase undergo a full epithelial-mesenchymal conversion and lose E-cadherin and ERalpha expression. Our data show that, although the E-cadherin gene becomes hypermethylated and heterochromatic, kinase inhibitors can restore E-cadherin expression, together with an epithelial morphology in an ERalpha-dependent fashion. Similarly, transfection of ERalpha, in the absence of ligands, was sufficient to restore E-cadherin transcription in both sfRON-T47D and other ERalpha-, E-cadherin-negative cells. Therefore, our results suggest a novel role for the ERalpha that plays the dual role of ligand-independent activator and ligand-dependent repressor of E-cadherin in breast cancer cells.
Research Interests:
Research Interests: Genetics, Gene expression, Europe, Temperature dependent sex determination, Sex ratio, and 15 moreFemale, Animals, Male, DNA methylation, CpG islands, Temperature, Early development, High Temperature, Enzyme, PLoS Genetics, Environmental Temperature, Bass, Base Sequence, Temperature Effect, and Gonads
Research Interests:
Research Interests:
Research Interests:
Research Interests: Stem Cells, Biological Sciences, Humans, Regulation of Gene Expression, Animals, and 13 moreCellular differentiation, Male, Phenotype, CHEMICAL SCIENCES, Neuronal Differentiation, Histones, Genetic variation, Zebrafish, Cell Fate, Embryos, Polycomb group proteins, Gene Expression Regulation, and X chromosome inactivation
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
We have previously described conjugates of L-arginine with aminoglycosides (AAC) that have shown anti-human immunodeficiency virus type 1 (HIV-1) activity in in vitro cell culture systems. Here, we extend our report to a novel neomycin... more
We have previously described conjugates of L-arginine with aminoglycosides (AAC) that have shown anti-human immunodeficiency virus type 1 (HIV-1) activity in in vitro cell culture systems. Here, we extend our report to a novel neomycin B-arginine conjugate (NeoR) that has shown up to 30-fold increased potency over previous AAC compounds. NeoR inhibited the replication of both R5 and X4 strains of HIV-1 in cells expressing the appropriate coreceptor or peripheral blood mononuclear cells. In lymphoid tissue ex vivo, NeoR blocked the replication of the dualtropic strain 89.6 suggesting anti-HIV activity of AAC on the site of in vivo virus replication. NeoR blocked the binding of HIV particles to lymphoid cells and was also able to antagonize the activity of the CXCR4 receptor so it may prevent the emergence of X4 HIV-1 strains. Nevertheless, in a cellular assay, we were unable to detect anti-Tat dependent transactivation activity as previously suggested for this family of compounds.
Research Interests:
The gp41 subunit of HIV-1 has been recently recognized as a target for antiviral therapy. C-34 is a peptide that mimics the heptad repeat 2 in the ectodomain of gp41. Here, we describe two HIV-1 strains selected after 5 and 17 passages in... more
The gp41 subunit of HIV-1 has been recently recognized as a target for antiviral therapy. C-34 is a peptide that mimics the heptad repeat 2 in the ectodomain of gp41. Here, we describe two HIV-1 strains selected after 5 and 17 passages in culture with increasing concentrations of C-34 (breakthrough concentration of 10 microg/ml). The HXB2-derived strain was more than 1000-fold resistant and contained a V38E mutation in the gp41 coding DNA sequence. The NL4-3-derived strain was more than 500-fold resistant and contained a L33S mutation in gp41. No cross-resistance to the RT inhibitor AZT, the HIV binding inhibitor dextran sulfate (DS), or the chemokine receptor antagonist ALX-40-4C was detected. These data indicate that HIV-1 can overcome C-34 inhibition through mutations at residues not involved in the formation of the hydrophobic cavity of gp41.
Research Interests:
Research Interests:
Research Interests:
We have studied the binding of biotinylated HIV particles to various cell lines and peripheral blood mononuclear cells (PBMCs). Viruses were harvested from cultures of cell surface-biotinylated cells productively infected with HIV-IIIB.... more
We have studied the binding of biotinylated HIV particles to various cell lines and peripheral blood mononuclear cells (PBMCs). Viruses were harvested from cultures of cell surface-biotinylated cells productively infected with HIV-IIIB. Labeled HIV particles bound to and infected CD4(+) cell lines and PBMCs. The interaction between gp120 and CD4 contributed in part to HIV binding to CD4(+) cells. However, HIV binding was for the most part independent of CD4 expression and sensitive to polyanion inhibition. Polyanion-sensitive interactions involved heparan sulfate in cell lines but not in primary T cells. Interestingly, HIV binding to primary cells was heterogeneous and targeted discrete subsets of CD4(+) and CD4(-) cells. The CD4(+) T cell subset that displayed high HIV-binding capacity contained mostly CD4(+)CD45RO(+) cells, whereas the subset showing undetectable HIV binding contained higher proportions of CD4(+)CD45RO(-) cells. Consistently, purified CD4(+)CD45RO(-) cells or purified CD4(+) T cells with low virus-binding capacity showed lower HIV entry and delayed HIV replication when compared with purified CD4(+)CD45RO(+) or purified CD4(+) T cells with high virus-binding capacity, respectively. Our data suggest that the binding of HIV to cell surface-expressed CD4 might be inefficient in a subset of CD4(+) T cells and that increased binding of HIV to activated and CD4(+)CD45RO(+) cells may contribute to the higher susceptibility of these cells to HIV infection.