Biomedical subjects

F Daniel-Vedele

Publications and source records attributed to F Daniel-Vedele.

23 records · Page 2Linked to original sources

PubMed1989

Cloning and analysis of the tomato nitrate reductase-encoding gene: protein domain structure and amino acid homologies in higher plants.

We have cloned and sequenced the nitrate reductase (NR)-encoding gene (nia) from tomato. When compared to the two Nicotiana tabacum nia structural genes, this 5-kb tomato gene shows a highly conserved structure, the coding sequence being interspersed with three introns at the same positions. Nucleotide sequences of the 5' promoter regions are not homologous, except for a 250-bp fragment. This small region might be involved in the similar regulation of the nia expression in tomato and tobacco plant species. The tomato gene codes for a 911 amino acid (aa) polypeptide chain. This sequence was aligned with and compared to other higher plant NR sequences. This alignment clearly identifies the three catalytic domains of NR, namely, a molybdopterin cofactor-binding domain, a heme domain and a FAD/NADH domain. On the other hand, it suggests that the less conserved 80-aa N-terminal region, containing a striking acidic aa cluster, is an additional domain bearing regulatory or structural function.

Amino Acid Sequence↗

PubMed1988

Expression of leaf nitrate reductase genes from tomato and tobacco in relation to light-dark regimes and nitrate supply.

The influence of light-dark cycles and nitrate supply on nitrate reductase (NR) mRNA levels was studied in two plant species, tobacco (Nicotiana tabacum) and tomato (Lycopersicon esculentum) using specific NR DNA probes. In the same series of experiments, changes in the levels of NR protein (NRP) by enzyme-linked immunosorbent assay and changes in the level of NADH-nitrate reductase activity (NRA) were also followed. During a light-dark cycle, it was found that in both tomato and tobacco, NR mRNA accumulation increased rapidly during the dark period and reached a maximum at the beginning of the day, while NRP reached a peak 2 and 4 hours after mRNA peaked, for tomato and tobacco, respectively. At the end of the day, the amount of mRNA was decreased by a factor of at least 100 compared to sunrise in both species. These results demonstrate that light is involved, although probably not directly, in the regulation of the NR gene expression at the mRNA level. The peak of NRA in tobacco coincided with the peak in NR mRNA accumulation (i.e. sunrise), whereas in tomato the peak of NRA was approximately 5 to 6 hours after sunrise. There is no obvious correlation between NRP and NRA levels during the day. In nitrogen starvation experiments, a rapid decrease of NRP and NRA was detected, while NR mRNA levels were not significantly altered. Upon nitrate replenishment, nitrogen-starved plants accumulated NR mRNA rapidly. These results suggest that the availability of nitrogen affects the expression of NR activity at the transcriptional as well as at the post-transcriptional levels.

Journal Article↗

PubMed1985

Functional analysis of the mouse H-2Kb gene promoter in embryonal carcinoma cells.

Mouse embryonal carcinoma (EC) cells do not express the major H-2 class I transplantation antigens. The latter, however, become detectable upon in vitro differentiation of EC cells. Neither class I H-2 genes nor the gene coding for beta-2 microglobulin (beta 2m) is transcribed in EC cells. We have constructed two hybrid plasmids containing the 5' flanking region of an H-2Kb gene followed by the coding regions of either the herpes simplex virus thymidine kinase (H-2 tk) or the chloramphenicol acetyl transferase (H-2 CAT) genes. Upon transfer into EC cells, the H-2 tk hybrid gene is expressed in F9 tk- cell lines which thus acquire a stable tk+ phenotype. When such transformed clones are induced to differentiate in vitro, tk activity shows a moderate increase, which reflects an increase in transcription of the hybrid gene. In transient transformation experiments, EC cells were found to express the H-2 CAT hybrid gene as well. We conclude that the 2 kilobase pair region of the H-2Kb gene which we used contains an active promoter region, but does not include all the elements required for the correct regulation of the H-2Kb gene.

Acetyltransferases↗

PubMed1985

H-2-restricted cytolysis of L cells doubly transformed with a cloned H-2Kb gene and cloned retroviral DNA.

We report the construction of target cells by the double transformation of mouse L cells with a cloned H-2Kb gene and molecular clones of Akv or Gross murine leukemia virus (MuLV) or the cloned gag gene of Akv MuLV. Cytolytic T lymphocytes (CTL) generated in BALB.B mice specific for Gross MuLV (closely related to Akv MuLV) kill these doubly transformed cells. This is a direct indication that a CTL subpopulation recognizes H-2Kb antigen in association with a viral antigen encoded by the gag gene of Gross MuLV.

AKR murine leukemia virus↗

PubMed1984

Functional expression of a mouse H-2Kb gene isolated from non-expressing teratocarcinoma cells.

Embryonal carcinoma cells do not express H-2 antigens or beta 2-microglobulin. Recent studies have suggested that the expression of these antigens is likely to be controlled at the level of transcription. To study the precise organization of the corresponding genes and their possible expression in adult mouse cells, we have isolated H-2-related genes from a genomic cosmid library constructed with PCC4-aza-RI from DNA of EC cells. Clones isolated from the library after stringent hybridization with an H-2 cDNA probe were tested for their ability to direct H-2 antigen synthesis after DNA-mediated gene transfer in a fibroblastic L cell. Four clones have been found to code for the major transplantation antigen H-2Kb. Structural analysis showed that these clones contained the same entire H-2Kb gene, identical to the corresponding gene isolated from differentiated C57Bl/10 cells. Furthermore, the present studies showed that this embryonal carcinoma gene was expressed and was functional when transfected into a differentiated cell.

Animals↗