Papers by Valeria Buggiano
Proceedings of the National Academy of Sciences of the United States of America, Jan 4, 2014
The roles of Argonaute proteins in cytoplasmic microRNA and RNAi pathways are well established. H... more The roles of Argonaute proteins in cytoplasmic microRNA and RNAi pathways are well established. However, their implication in small RNA-mediated transcriptional gene silencing in the mammalian cell nucleus is less understood. We have recently shown that intronic siRNAs cause chromatin modifications that inhibit RNA polymerase II elongation and modulate alternative splicing in an Argonaute-1 (AGO1)-dependent manner. Here we used chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) to investigate the genome-wide distribution of AGO1 nuclear targets. Unexpectedly, we found that about 80% of AGO1 clusters are associated with cell-type-specific transcriptional enhancers, most of them (73%) overlapping active enhancers. This association seems to be mediated by long, rather than short, enhancer RNAs and to be more prominent in intragenic, rather than intergenic, enhancers. Paradoxically, crossing ChIP-seq with RNA-seq data upon AGO1 depletion revealed that enhancer-bound AG...
Resumen La experiencia de trabajo con alumnos de 1 año del nivel secundario destaca la importanci... more Resumen La experiencia de trabajo con alumnos de 1 año del nivel secundario destaca la importancia del trabajo colaborativo entre docentes y entre estudiantes para generar mejores aprendizajes en el área de Ciencias Naturales. La actividad implica el trabajo en pareja docente dentro del marco de la formación docente continua y en servicio del Colegio. Los logros obtenidos con la experiencia ponen en evidencia el desarrollo de competencias de trabajo colaborativo, la estimulación del pensamiento científico y de la creatividad con el uso responsable de recursos tecnológicos. Es destacable la incidencia del encuentro y el trabajo de tres profesores en un espacio institucional pensado como promotor de mejores prácticas de enseñanza y aprendizaje. El uso de espacios institucionales para el trabajo con pares docentes permite la integración de diferentes áreas de enseñanza y la profundización en mejores trayectorias de aprendizaje. La instalación de experiencias similares requiere del acom...
Journal of …, 1997
JOURNAL OF VIROLOGY, 0022-538X/97/$04.000 May 1997, p. 38953903 ... Generation of a Tumorigenic ... more JOURNAL OF VIROLOGY, 0022-538X/97/$04.000 May 1997, p. 38953903 ... Generation of a Tumorigenic Milk-Borne Mouse Mammary Tumor ... TATYANA V. GOLOVKINA,1 ISABEL PIAZZON,2 IRENE NEPOMNASCHY,2 VALERIA BUGGIANO,2 MARTA DE OLANO ...
Revista …, 1997
... MURINO ISABEL PIAZZON1, IRENE NEPOMNASCHY1, VALERIA BUGGIANO2, PEDRO BEKINSCHTEIN3, ALEJANDRA... more ... MURINO ISABEL PIAZZON1, IRENE NEPOMNASCHY1, VALERIA BUGGIANO2, PEDRO BEKINSCHTEIN3, ALEJANDRA GOLDMAN2, PAULA BERGUER, ADRIANA DEROCHE1, GABRIELA ... que habían adquiri-do el SAg del provirus endógeno Mtv-7 se gene-raban en los ...
Journal of Cell Biology
In mammals, argonaute (AGO) proteins have been characterized for their roles in small RNA–mediate... more In mammals, argonaute (AGO) proteins have been characterized for their roles in small RNA–mediated posttranscriptional and also in transcriptional gene silencing. Here, we report a different role for AGO1 in estradiol-triggered transcriptional activation in human cells. We show that in MCF-7 mammary gland cells, AGO1 associates with transcriptional enhancers of estrogen receptor α (ERα) and that this association is up-regulated by treating the cells with estrogen (E2), displaying a positive correlation with the activation of these enhancers. Moreover, we show that AGO1 interacts with ERα and that this interaction is also increased by E2 treatment, but occurs in the absence of RNA. We show that AGO1 acts positively as a coactivator in estradiol-triggered transcription regulation by promoting ERα binding to its enhancers. Consistently, AGO1 depletion decreases long-range contacts between ERα enhancers and their target promoters. Our results point to a role of AGO1 in transcriptional r...
Early detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been prov... more Early detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been proven crucial during the efforts to mitigate the effects of the COVID-19 pandemic. Several diagnostic methods have emerged in the past few months, each with different shortcomings and limitations. The current gold standard, RT-qPCR using fluorescent probes, relies on demanding equipment requirements plus the high costs of the probes and specific reaction mixes. To broaden the possibilities of reagents and thermocyclers that could be allocated towards this task, we have optimized an alternative strategy for RT-qPCR diagnosis. This is based on a widely used DNA-intercalating dye and can be implemented with several different qPCR reagents and instruments. Remarkably, the proposed qPCR method performs similarly to the broadly used TaqMan-based detection, in terms of specificity and sensitivity, thus representing a reliable tool. We think that, through enabling the use of vast range of thermocyc...
Journal of virology, 1999
Mouse mammary tumor virus (MMTV) infects both lymphoid tissue and lactating mammary gland during ... more Mouse mammary tumor virus (MMTV) infects both lymphoid tissue and lactating mammary gland during its infectious cycle, but some endogenous MMTVs are transcribed only in lymphoid cells. We found a lymphoid cell-specific endogenous MMTV that was converted to a milk-borne, infectious virus through recombination with an exogenously transmitted MMTV. The changed expression pattern correlated with the alteration of a single base pair in the long terminal repeat of the lymphoid cell-specific virus. Transgenic mice with the element from either the milk-borne or lymphoid cell-specific virus upstream of the chloramphenicol acetyltransferase reporter gene showed the same pattern of expression as the virus from which the regulatory sequences were derived. Electrophoretic mobility shift assays with mammary cell extracts showed that the site from the milk-borne virus was preferentially bound by a prolactin-inducible factor that poorly bound the altered site from the lymphoid cell-specific virus. ...
Medicina, Aug 1, 1997
... MURINO ISABEL PIAZZON1, IRENE NEPOMNASCHY1, VALERIA BUGGIANO2, PEDRO BEKINSCHTEIN3, ALEJANDRA... more ... MURINO ISABEL PIAZZON1, IRENE NEPOMNASCHY1, VALERIA BUGGIANO2, PEDRO BEKINSCHTEIN3, ALEJANDRA GOLDMAN2, PAULA BERGUER, ADRIANA DEROCHE1, GABRIELA ... que habían adquiri-do el SAg del provirus endógeno Mtv-7 se gene-raban en los ...
Scand J Immunol, 2008
The T-cell repertoire is shaped by the positive and negative selection of immature CD4(+) CD8(+) ... more The T-cell repertoire is shaped by the positive and negative selection of immature CD4(+) CD8(+) double positive (DP) thymocytes. Positive selection of DP T cells to the CD4(+) CD8(-) and CD4(-) CD8(+) simple positive (SP) lineages is a multistep process which involves cellular interactions between thymocytes and stromal cells. Mutant nackt (nkt/nkt) mice have been shown to have a deficiency in the CD4(+) CD8(-) T-cell subset both in the thymus and in the periphery. The present report suggests that nkt/nkt mice present alterations in early steps of positive selection because they show decreases in the percentages of CD69(+) and CD5(+) cells within the DP subset. Experiments involving bone marrow transfer and thymic chimeras demonstrate that the thymic epithelium of nkt/nkt mice is involved in the alterations registered during positive selection and dictates the ultimate fate of CD4(+) SP cells.
Environmental Research, 2015
Alternative pre-mRNA splicing plays key roles in determining tissue- and species-specific cell di... more Alternative pre-mRNA splicing plays key roles in determining tissue- and species-specific cell differentiation as well as in the onset of hereditary disease and cancer, being controlled by multiple post- and co-transcriptional regulatory mechanisms. We report here that airborne particulate matter, resulting from industrial pollution, inhibits expression and specifically affects alternative splicing at the 5' untranslated region of the mRNA encoding the bone morphogenetic protein BMP4 in human colon cells in culture. These effects are consistent with a previously reported role for BMP4 in preventing colon cancer development, suggesting that ingestion of particulate matter could contribute to the onset of colon cell proliferation. We also show that the underlying mechanism might involve changes in transcriptional elongation. This is the first study to demonstrate that particulate matter causes non-pleiotropic changes in alternative splicing.
Medicina, 1997
Mouse mammary tumor virus (MMTV) is a type B retrovirus that is transmitted as an infectious milk... more Mouse mammary tumor virus (MMTV) is a type B retrovirus that is transmitted as an infectious milk-borne particle and that causes mammary carcinomas by insertional activation of cellular protooncogenes. Germ line infections result in endogenous Mtv proviruses integrated in the genome of most mouse strains. These endogenous proviruses have been integrated into the genomes of mice for only the past 3-5 million years. The open reading frame present in the 3' long terminal repeat (LTR) of the provirus encodes a superantigen (SAg) which is able to stimulate a large proportion of T cells sharing a common T-cell receptor beta chain variable domain (v beta). Expression of this SAg is critical to the MMTV life cycle. After expression of the SAg in B cells a significant number of T cells are recruited to respond to these MMTV infected cells. As a consequence both the T cells expressing the relevant TCR V beta domain and the infected B cells become activated and start dividing. This would f...
Journal of virology, 1997
Two novel exogenous mouse mammary tumor viruses (MMTV), BALB2 and BALB14, that encode superantige... more Two novel exogenous mouse mammary tumor viruses (MMTV), BALB2 and BALB14, that encode superantigens (Sags) with Vbeta2+ and Vbeta14+ specificities, respectively, were found in the BALB/cT mouse strain. BALB/cT females were crossed with AKR/J males to generate F1 females. Foster nursing of BALB/cT mice on (BALB/cT x AKR/J)F1 mothers resulted in the generation of a new mouse strain, BALB/cLA, that had acquired a new exogenous MMTV (hereafter called LA) with a Vbeta6+/Vbeta8.1+-T-cell-specific Sag. Sequence analysis of the long terminal repeats of the BALB2, BALB14, and LA viruses indicated that LA virus resulted from recombination between BALB14 and the endogenous Mtv-7 provirus. Mtv-7 is expressed only in lymphoid tissues but not the mammary glands of Mtv-7-containing mouse strains such as AKR. In contrast, LA virus was highly expressed in the mammary gland, although it had the sag-specific region from Mtv-7. The LA virus, as well as different recombinant viruses expressed in the mam...
Medicina, 1995
A number of milk-borne exogenous mammary tumor viruses (MMTV) infect mice shortly after birth and... more A number of milk-borne exogenous mammary tumor viruses (MMTV) infect mice shortly after birth and, when expressed, produce superantigens. The expression of these superantigens mediate the progressive deletion of T cells expressing specific V beta products. Here we describe a maternally-inherited alteration in the T cell repertoire in one colony of BALB/c mice which has not been reported up to now. This alteration involves the deletion of V beta 2+ and 14+ CD4+ T cells and correlates with a high incidence of mammary tumors, suggesting the involvement of a superantigen(s) probably transmitted through an exogenous MMTV in milk.
Medicina, 1989
The existence of parental influences on the recognition of self histocompatibility was investigat... more The existence of parental influences on the recognition of self histocompatibility was investigated. The results obtained showed that: 1) fetal liver and neonatal splenocytes and thymocytes from F1 mice differed in their capacity to regulate parental alloreactive T reactions against self histocompatibility antigens either of maternal or paternal origin. Fetal and neonatal F1 cells--until day 5--were able to suppress systemic and local GvH reactions induced in F1 hosts with maternal but not with paternal splenocytes; 2) this differential regulatory activity concerning parental GvH reactions against self histocompatibility antigens are correlated with the existence of a differential time lag in the appearance of thymic contrasuppressor activity on maternal anti-paternal and paternal anti-maternal GvH reactivity; 3) splenocytes from reciprocal F1 hybrids--from day 14 onwards--differed in their ability to stimulate F1 T cell proliferation in SMLC reactions; 4) foster nursing of F1 hybri...
Scandinavian Journal of Immunology, 2008
The T-cell repertoire is shaped by the positive and negative selection of immature CD4 1 CD8 1 do... more The T-cell repertoire is shaped by the positive and negative selection of immature CD4 1 CD8 1 double positive (DP) thymocytes. Positive selection of DP T cells to the CD4 1 CD8 2 and CD4 2 CD8 1 simple positive (SP) lineages is a multistep process which involves cellular interactions between thymocytes and stromal cells. Mutant nackt (nkt/nkt) mice have been shown to have a deficiency in the CD4 1 CD8 2 T-cell subset both in the thymus and in the periphery. The present report suggests that nkt/nkt mice present alterations in early steps of positive selection because they show decreases in the percentages of CD69 1 and CD5 1 cells within the DP subset. Experiments involving bone marrow transfer and thymic chimeras demonstrate that the thymic epithelium of nkt/nkt mice is involved in the alterations registered during positive selection and dictates the ultimate fate of CD4 1 SP cells.
Nature Structural & Molecular Biology, 2009
When targeting promoter regions, small interfering RNAs (siRNAs) trigger a previously proposed pa... more When targeting promoter regions, small interfering RNAs (siRNAs) trigger a previously proposed pathway known as transcriptional gene silencing by promoting heterochromatin formation. Here we show that siRNAs targeting intronic or exonic sequences close to an alternative exon regulate the splicing of that exon. The effect occurred in hepatoma and HeLa cells with siRNA antisense strands designed to enter the silencing pathway, suggesting hybridization with nascent pre-mRNA. Unexpectedly, in HeLa cells the sense strands were also effective, suggesting that an endogenous antisense transcript, detectable in HeLa but not in hepatoma cells, acts as a target. The effect depends on Argonaute-1 and is counterbalanced by factors favoring chromatin opening or transcriptional elongation. The increase in heterochromatin marks (dimethylation at Lys9 and trimethylation at Lys27 of histone H3) at the target site, the need for the heterochromatin-associated protein HP1a and the reduction in RNA polymerase II processivity suggest a mechanism involving the kinetic coupling of transcription and alternative splicing.
Laboratory Animals, 1998
A genetic monitoring of the BALB/c mouse foundation colony in our animal facility was carried out... more A genetic monitoring of the BALB/c mouse foundation colony in our animal facility was carried out. The techniques of choice were skin grafting, coat colour test, flow cytometric analysis for H2 antigens (loci H2-D and H2-A), electrophoretic analysis of isoenzymes (loci Idh1, Pep3, Es3 and Mod1), PCR-amplified microsatellites (loci Igh-V, Ngfg, Plau, Crp, Igh, D16Mit5, D3Mit49 and D17Mit16) and DNA fingerprinting (multilocus probes 33.6, 33.15 and (CAC)5). No evidence of genetic contamination was found, ruling out the possibility of an outcross with AKR, the other albino strain maintained at the facility. Nevertheless, DNA fingerprint patterns revealed evidence of genetic heterogeneity in four out of nine lines of the nucleus colony, interpreted as minisatellite mutations favoured for a single line system with more than 40 generations of separation from the ancestral pair. These mice are mainly used in cancer and immunological research within the institute.
Journal of Reproductive Immunology, 1991
The ability of fetal and neonatal F1 thymocytes to regulate parental graft versus host (GvH) reac... more The ability of fetal and neonatal F1 thymocytes to regulate parental graft versus host (GvH) reactions against self histocompatibility antigens was investigated. The results obtained showed that: (1) fetal F1 thymocytes were able to suppress both maternal and paternal GvH reactivity; (2) at birth, thymocytes were still able to suppress maternal GvH reactivity while no suppression of paternal reactions was detected; the ability to suppress maternal GvH reactions could be detected until day 3; (3) the loss of suppressor activity correlated with the ability of thymocytes to contrasuppress parental GvH reactions. Thus, 24-h F1 thymocytes showed contrasuppressor activity on paternal GvH reactivity and 4-day thymocytes on maternal reactivity. Thymic cells with contrasuppressor activity were shown to be Lyt-1+, CD4+, CD8- and adherent to Vicia villosa. These results suggest the existence of parental effects influencing the duration of thymic suppression and the subsequent appearance of contrasuppressor activity on GvH reactions against self histocompatibility antigens, according to the maternal or paternal origin of self antigens towards which the reaction is directed.
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Papers by Valeria Buggiano