Biomedical subjects

P Marc

Publications and source records attributed to P Marc.

9 recordsLinked to original sources

PubMed2001

Transcriptional induction of repair genes during slowing of replication in irradiated Saccharomyces cerevisiae.

We investigated the inhibition of cell-cycle progression and replication and the induction of the transcriptional response in diploid budding yeast populations exposed to two different doses of gamma-rays resulting in 15 and 85% survival respectively. We studied the kinetics of the cellular response to ionizing treatment during the period required for all of the surviving cells to achieve at least one cell division. The length of these periods increased with the dose. Irradiated populations arrested as large-budded cells containing partially replicated chromosomes. The extent of the S-phase was proportional to the amount of damage and lasted 3 or 7h depending on the irradiation dose. In parallel to the division study, we carried out a kinetic analysis of the expression of 126 selected genes by use of dedicated microarrays. About 26 genes were induced by irradiation and displayed various pattern of expression. Interestingly, 10 repair genes (RAD51, RAD54, CDC8, MSH2, RFA2, RFA3, UBC5, SRS2, SPO12 and TOP1), involved in recombination and DNA synthesis, display similar regulation of expression in the two irradiated populations. Their pattern of expression were confirmed by Northern analysis. At the two doses, the expression of this group of genes closely followed the extended replication period, and their expression resumed when replication restarted. These results suggest that the damage-induced response and DNA synthesis are closely regulated during repair. The analysis of the promoter regions indicates a high occurrence of the three MCB, HAP and UASH regulatory boxes in the promoters of this group of genes. The association of the three boxes could confer an irradiation-replication specific regulation.

Blotting, Northern↗

PubMed2001

yMGV: a database for visualization and data mining of published genome-wide yeast expression data.

The yeast Microarray Global Viewer (yMGV) is an on-line database providing a synthetic view of the transcriptional expression profiles of Saccharomyces cerevisiae genes in most of the published expression datasets. yMGV displays a one-screen graphical representation of gene expression variations for each published genome-wide experiment, allowing quick retrieval of experimental conditions affecting expression of this gene. yMGV also provides tools to isolate groups of genes sharing similar transcription profiles in a defined subset of experiments. Additionally, yMGV furnishes a set of statistical tools for critical assessment of published data. We therefore believe that yMGV is an efficient tool that affords a quick and comprehensive overview of microarray data and generates new gene classifications. As of 20 March 2001 the yMGV database contains 6 000 000 measurements, representing genome-wide expression comparisons of 932 experiments from 39 microarray publications. The yMGV interface is available at http://transcriptome.ens.fr/ymgv/.

Computational Biology↗

PubMed2001

Transcriptomes, transcription activators and microarrays.

Gene-specific transcription activators are among the main factors which specifically shape the transcriptome profiles. It is tempting to take advantage of their properties to decipher the genome expression circuitry. The advent of microarray technology has offered fantastic opportunities to quickly analyze the expression profiles dictated by specific transcription factors. This review will first focus on the strategies which have been devised to control the activity of transcription factors and in the second part on the microarray experiments which addressed the role of these transcription factors in the genome-wide expression profile. This last part will mainly consider the case of the yeast Saccharomyces cerevisiae genome. All the collected data are available through the on-line database yTAFNET (http://transcriptome.ens.fr/ytafnet/). yTAFNET is designed to help the characterization of connections between the different yeast regulatory networks.

Databases, Factual↗

PubMed2001

An artificial transcription activator mimics the genome-wide properties of the yeast Pdr1 transcription factor.

We analysed the genome-wide regulatory properties of an artificial transcription activator in which the DNA-binding domain of the yeast transcription factor, Pdr1, was fused to the activation domain of Gal4 (Pdr1*GAD). This Pdr1*GAD chimera was put under the control of the inducible GAL1 promoter. DNA microarray analyses showed that all the target genes upregulated by the well-studied native gain-of-function Pdr1-3 mutant were similarly activated by the chimerical factor Pdr1*GAD upon galactose induction. Additionally, this kinetic approach led us not only to confirm previously published targets, but also to define a hierarchy among members of the Pdr1 regulon. Our observations prove, for the first time at the complete genome level, that the DNA-binding domain of Pdr1 is sufficient to guide its specificity. We propose that this approach could be useful for the study of new transcription factors identified in silico from sequenced organisms. Complete data are available at www.biologie.ens.fr/yeast-publi.html.

Cells, Cultured↗

PubMed2000

Genome microarray analysis of transcriptional activation in multidrug resistance yeast mutants.

The cDNA from activated mutants of the homologous transcription factors Pdr1p and Pdr3p was used to screen DNA microarrays of the Saccharomyces cerevisiae complete genome. Twenty-six overexpressed targets of the PDR1-3 and/or PDR3-7 mutants were identified. Twenty-one are new targets, the majority of which are of unknown function. In addition to well known ABC transporters, these targets appear to be involved in transport or in membrane lipids and cell wall biosyntheses. Several of the targets seem to contribute to the cell defence against a variety of stresses. Pdr1p and Pdr3p do not act similarly on all targets. Unexpectedly, the expression of 23 other genes appeared to be repressed in the PDR1-3 and/or PDR3-7 mutants. In contrast to the majority of the activated genes, none of the repressed genes contains pleiotropic drug resistance binding sites in their promoter.

Base Sequence↗

PubMed2000

Human growth hormone stimulates proteinase activities of rabbit bone cells via IGF-I.

Human growth hormone (hGH) and human insulin-like growth factor-I (hIGF-I) are known to have a marked influence on osteoclastic formation and bone resorption in an unfractionated rabbit bone cell model. This study investigated the effects of both of these factors on the induction of cysteine-proteinases and matrix metalloproteinase-2 (MMP-2) and MMP-9. After 4 days of rabbit bone cell culture, hGH and hIGF-I significantly modulated cathepsin, MMP-9 (latent form) and MMP-2 (active form) activities. Similar studies were performed in the presence of parathyroid hormone (hPTH). hPTH increased MMP-2 and MMP-9 activities whereas it had no effect on the production of cathepsins by bone cells. When neutralizing anti-hIGF-1 antiserum was added to the culture, the stimulatory effects of hGH were totally abolished, indicating that hGH-modulated cathepsin and metalloproteinase activities were partly mediated by local hIGF-I secretion. Cysteine-proteinase activities released by purified osteoclasts were very low and were not modulated by hGH and h-IGF-I. However, hIGF-I but not hGH increased MMP-2 and MMP-9 activities released by purified osteoclasts. It may be concluded that hGH markedly stimulates the expression of proteinases in total rabbit bone cells via local hIGF-I production by stromal cells. Cysteine-proteinase activities are mainly produced by non-osteoclastic cells, while MMP-2 and MMP-9 modulated by hIGF-I are mainly expressed by osteoclastic cells.

Animals↗

PubMed1992

Antibodies to varicella-zoster virus modulate antigen distribution but fail to induce viral persistence in vitro.

Varicella-zoster virus (VZV) persists in human sensory ganglia. One of the hypotheses to explain the induction or the maintenance of VZV latency is that it could be promoted by the immune response itself. It is known that in the case of viruses which bud off the infected cell membrane, virus-specific antibodies can induce antigenic modulation, i.e., spatial redistribution of viral antigens and modulation of their synthesis. To determine whether antigenic modulation occurs during VZV infection in vitro and could possibly be involved in viral persistence, we have grown infected cells in the presence of anti-VZV antibodies either transiently or permanently. The distribution of immune complexes and viral proteins was then analyzed. In transient immunomodulation experiments, the distribution of one or more viral antigens was modified not only in the cytoplasmic membranes but also in the cytoplasm and nucleoplasm of infected cells. When infected cells were kept permanently in the presence of antibodies, the same pattern of redistribution of immune complexes was observed and the localization of internal viral glycoproteins was significantly modified. However, antibodies did not prevent the lytic effect of infection; they altered neither the infectious virus yield nor the Western immunoblot pattern of viral proteins, suggesting that immunomodulation is not the primary effector of viral persistence.

Antibodies, Viral↗

PubMed1990

An in vivo model of varicella-zoster virus latent infection of dorsal root ganglia.

We describe here the first in vivo model of varicella-zoster virus (VZV) latent infection in the adult rat peripheral nervous system. Infected Mewo cells were injected subcutaneously along the spine of healthy adult rats. No clinical sign of infection was observed even 9 months after inoculation. Humoral immune response to VZV was detected in all infected animals throughout the study (9 months). The presence of viral material in dissociated and cultured dorsal root ganglia (DRG) from inoculated animals was studied by immunoperoxidase and in situ hybridization. When DRGs from infected animals were plated in culture from 1 month and up to 9 months after inoculation, viral nucleic acids and proteins were detected in neurons. Furthermore, trypsinization and subcultivation of infected neurons in culture is needed to reactivate infectious virus at least in some of the neurons. This model provides a useful tool for studying 1) the molecular mechanisms leading to an in vivo latency, 2) the role of the immune system, in particular cellular immunity, on the establishment, maintenance, and reactivation of latency, 3) the neurotropism of mutant viruses, and 4) the effects of antiviral agents.

Animals↗

PubMed1990

Acute and persistent varicella-zoster virus infection of human and murine neuroblastoma cell lines.

Human and murine neuroblastoma cell lines were infected in vitro with varicella-zoster virus (VZV). Infected human neuroblastoma cells (IMR-32) supported the synthesis of abundant viral antigens as detected by indirect immunoperoxidase labeling using human serum rich in anti-VZV antibodies and did not survive the infection. In situ hybridization (ISH) with VZV-cloned probes revealed a strong hybridization signal in these infected cells. During cultivation, the virus was released in the culture medium, and viral polypeptides were revealed by Western blotting of infected cells, using either a monoclonal anti-gpI antibody or a rabbit antiserum. All these findings indicate that IMR-32 cells support a productive and lytic infection by VZV, whether infected by cell-free virus or by cocultivation with infected cells. Murine neuroblastoma cells (neuro-2A) survived VZV infection and did not produce any infectious virus. No VZV-specific proteins were detected in infected cells either by immunolabeling or by Western blotting. However, viral nucleic acids could be detected by ISH, indicating that mouse neuroblastoma cells displayed a nonproductive, nonlytic infection. Infected neuro-2A cells have been examined by ISH using probes corresponding to immediate early (IE) genes 4, 62, and 63 and late (L) gene 31 encoding gpII. A strong hybridization signal was detected when infected cells were probed with a fragment containing the IE genes 62 and 63. Lower levels of hybridization were detected with the other probes, corresponding to IE or L genes. These systems allow comparative molecular analysis of persistent and acute infection of nerve cells by VZV.

Animals↗