Biomedical subjects

Valeria Berno

Publications and source records attributed to Valeria Berno.

5 recordsLinked to original sources

PubMed2006

Estrogen-receptor-alpha exchange and chromatin dynamics are ligand- and domain-dependent.

We report a mammalian-based promoter chromosomal array system developed for single-cell studies of transcription-factor function. Designed after the prolactin promoter-enhancer, it allows for the direct visualization of estrogen receptor alpha (ERalpha) and/or Pit-1 interactions at a physiologically regulated transcription locus. ERalpha- and ligand-dependent cofactor recruitment, large-scale chromatin modifications and transcriptional activity identified a distinct fingerprint of responses for each condition. Ligand-dependent transcription (more than threefold activation compared with vehicle, or complete repression by mRNA fluorescent in situ hybridization) at the array correlated with its state of condensation, which was assayed using a novel high throughput microscopy approach. In support of the nuclear receptor hit-and-run model, photobleaching studies provided direct evidence of very transient ER-array interactions, and revealed ligand-dependent changes in k(off). ERalpha-truncation mutants indicated that helix-12 and interactions with co-regulators influenced both large-scale chromatin modeling and photobleaching recovery times. These data also showed that the ERalpha DNA-binding domain was insufficient for array targeting. Collectively, quantitative observations from this physiologically relevant biosensor suggest stochastic-based dynamics influence gene regulation at the promoter level.

Active Transport, Cell Nucleus↗

PubMed2006

High-resolution, high-throughput microscopy analyses of nuclear receptor and coregulator function.

Steroid nuclear receptors are ligand-dependent transcription factors that have been studied since the early 1960s by principally biochemical and reporter assay approaches. From these studies an elegant and complex model of nuclear receptor transcription regulation has been developed. Inherent to both biochemical and reporter assay approaches is the generation of averaged responses and it is not generally considered that individual cells could exhibit quite varied responses. In some cases, recent microscopic single-cell analyses provide markedly different responses relative to traditional approaches based on population averaging and underscore the need to continue refinement of the current model of nuclear receptor-regulated transcription. While single-cell analyses of nuclear receptor action have been hindered by the predominantly qualitative nature of the approach, high-throughput microscopy is now available to resolve this issue. This chapter demonstrates the utility of high-throughput microscopic analyses of nuclear receptor and nuclear receptor coregulator function. The ability of high-throughput microscopy to generate physiologically appropriate test populations by filtering based on morphological and protein of interest expression criteria is demonstrated. High-resolution, high-throughput microscopy is illustrated that provides quantitative subcellular information for both androgen and estrogen receptors. Efforts are ongoing to develop model systems that provide additional multiplex data and with refined image analyses to achieve true high-content imaging screens.

Algorithms↗

PubMed2005

Simultaneous expression of caveolin-1 and E-cadherin in ovarian carcinoma cells stabilizes adherens junctions through inhibition of src-related kinases.

Cadherin-mediated adhesion plays an important role in maintaining cell-cell contacts and reducing tumor metastasis. However, neo-expression of E-cadherin in ovarian carcinoma does not prevent the release and spread of cells from the primary tumor. Because caveolin-1 is down-regulated concomitantly with E-cad expression, we investigated whether the stability of adherens junctions in ovarian carcinoma was affected by caveolin-1 expression. We used IGROV1 cells transfected with caveolin-1 (IGtC3), mock-transfected control cells (IGtM87), and SKOV3 cells that endogenously express caveolin-1. Simultaneous expression of caveolin-1 and E-cadherin favored membrane distribution of E-cadherin and its associated catenin (p120ctn), even when caveolin-1 was only focally associated with adherens junctions. Silencing of caveolin-1 induced intracellular E-cadherin redistribution in IGtC3 and SKOV3 cells. Treatment with the specific src kinase inhibitor PP1 increased E-cadherin expression in IGtM87 and SKOV3 cells and enhanced membrane localization of both E-cadherin and p120ctn. However, PP1 could not completely reverse the detrimental effects on cell-cell adhesion induced by Ca2+ depletion in IGtM87 cells. Together, our data suggest that caveolin-1 expression indirectly promotes cell-cell adhesion in ovarian carcinoma cells by a mechanism involving inhibition of src-related kinases. Thus, down-regulation or loss of caveolin-1 might contribute significantly to the spread of tumor cells from the primary tumor.

Adherens Junctions↗

PubMed2004

Immunological and pathobiological roles of fibulin-1 in breast cancer.

Fibulin-1 (Fbln-1) is an immunogenic breast cancer-related glycoprotein identified by serological analysis of cDNA expression library (SEREX) strategy. Here, we show that dendritic cells from two breast cancer patients elicited a CD4(+)-mediated T-cell response to Fbln-1 presentation. In both patients, an antibody response to Fbln-1 was also found. By contrast, a Fbln-1-seronegative patient and a weakly seropositive patient demonstrated no such T-cell response. Analysis of human breast cancers for Fbln-1 RNA and protein expression revealed the presence of Fbln-1C and -1D variants. Fbln-1 was detected in the cytoplasm and at the cell surface of different human breast carcinoma cell lines. Immunohistochemical analysis of 528 archival primary breast carcinomas showed the expression of Fbln-1 in 35% of the cases. When the immunohistochemical findings were compared against pathobiological information associated with each specimen, an inverse relationship between Fbln-1 and cathepsin D expression was observed (P=0.04). Furthermore, even though long-term survival was similar between Fbln-1-positive and -negative cases, the survival of Fbln-1-positive cases improved when a lymphoid infiltrate was present at the tumour site. Taken together, our findings of an Fbln-1-specific immunity and the improved survival associated with Fbln-1 expression in the presence of lymphoid infiltration point to a role of Fbln-1 in tumour immunosurveillance.

Antibodies, Monoclonal↗

PubMed2002

p53-dependent downregulation of metastasis-associated laminin receptor.

Based on observations suggesting a role for the tumor suppressor protein p53 in regulating expression of the 67-kDa laminin receptor precursor, 37LRP, we analysed the 37LRP promoter activity in a wild-type p53 (wt p53) ovarian carcinoma cell line and in a cisplatin-resistant subline with mutated p53. We observed an increased promoter activity in wt p53 cells as compared to the mutated-p53 line when the first intron of the 37LRP gene was present in the reporter construct. Cotransfection experiments showed that the promoter is downregulated by both wt and mutated p53. Deletion analysis of the first intron localized an enhancer activity in the first 5' 214 bp that upregulates both 37LRP and SV40 promoter activity and is repressed by both wt and mutant p53. Cotransfection, mutagenesis and gel-shift experiments identified a functional AP-2 cis-acting element in this intron region that is repressed by increased levels of both wt and mutated p53. Coimmunoprecipitation studies revealed AP-2 in physical association in vivo with both wt and mutated p53, indicating for the first time that interaction of p53 with AP-2 is involved in the repression mechanism and in the regulation of genes involved in cancer growth and progression.

Base Sequence↗