Biomedical subjects

J Delcour

Publications and source records attributed to J Delcour.

At least 55 records · Page 3Linked to original sources

PubMed1987

Cloning and nucleotide sequence of different iso-IS231 elements and their structural association with the Tn4430 transposon in Bacillus thuringiensis.

A family of five repetitive sequences (RS) has been isolated from a plasmid DNA library of Bacillus thuringiensis strain berliner 1715. In a previous paper [Mahillon et al., EMBO J. 4(1985)3895-3899] one of these was shown to harbor all the features of an IS element (IS231). Further nucleotide sequence analysis revealed that two other RS, flanking the delta-endotoxin gene, are actually variants of IS231. Comparison of the nucleotide sequences surrounding the iso-IS231 elements showed a unique structural association between some of these elements and the transposon Tn4430. Although these IS231 elements have transposed into Tn4430, both these IS231 s and the transposon Tn4430 remain structurally intact.

Bacillus thuringiensis↗

PubMed1985

Nucleotide sequence and structural organization of an insertion sequence element (IS231) from Bacillus thuringiensis strain berliner 1715.

This paper describes the structural organization of a repetitive DNA sequence isolated from plasmids of Bacillus thuringiensis strain berliner 1715. DNA sequence analysis of this repetitive sequence (RS) revealed all the characteristic features of an insertion sequence (IS). This 1656-bp element is delineated by two 20-bp inverted repeats which are flanked by two 11-bp direct repeats. A long open reading frame spans almost the entire sequence and is preceded by potential transcriptional and translational signals. A structural homology was observed between this RS and the Escherichia coli IS4 element in the length of their direct repeats, the sequence of their inverted repeats and the sequence of their putative transposases. These data strongly suggest that this sequence is an authentic insertion sequence. Therefore the name IS231 is proposed for this first Bacillus IS element. Further relationships with other known IS sequences were also found and are discussed.

Amino Acid Sequence↗

PubMed1985

In vitro methylation of undermethylated yeast poly(A)-rich RNA using mRNA(guanine-7-)-methyltransferase purified from wheat germ or yeast.

By crossing two strains of Saccharomyces cerevisiae deficient for each of the two methionine adenosyltransferase isoenzymes (ATP: L-methionine S-adenosyltransferase EC 2.5.1.6) respectively, we have constructed a strain strictly auxotrophic for S-adenosylmethionine and used it as a source of undermethylated mRNA suitable for in vitro transmethylation studies. RNA has been phenol-extracted from yeast cells shifted down to S-adenosylmethionine-free medium for 90 min and poly(A)-rich RNA has been prepared by oligo(dT)-cellulose chromatography. Upon incubation in vitro in the presence of methyl-labeled S-adenosylmethionine and mRNA (guanine-7-)-methyltransferase purified from wheat germ or yeast, undermethylated poly(A)-rich RNA became significantly labeled as compared to non-starved cells from the same strain, or from a wild-type control. Cap structures were resolved by paper chromatography afer T2 and P1 RNase digestion, and shown to be a mixture of m7G5'ppp5'G and m7G5'ppp5'A, irrespective of the enzyme source, in agreement with earlier in vivo studies in yeast mRNA capping and methylation.

Methylation↗

PubMed1983

Partial purification and characterization of mRNA (guanine-7-) methyltransferase from the yeast Saccharomyces cerevisiae.

As a tool for the study of the capping-methylation process of yeast mRNA, we developed a procedure for the purification of the mRNA (guanine-7-)methyltransferase using the commercial cap analog guanosine(5')triphospho(5')guanosine as a substrate and radioactive S-adenosylmethionine (AdoMet) as the methyl group donor. The osmotic-sensitive yeast strain VY 1160 was used as the enzyme source. Little methyltransferase activity was detectable in a crude lysate obtained after osmotic shock. We showed that this was due to the presence of a low-molecular-weight inhibitor which could easily be eliminated by Sephadex G-25 gel filtration. The 10000 X g supernatant from the crude lysate was submitted to DEAE-cellulose and DNA-agarose chromatography. The resulting preparation was enriched about 450-fold in specific activity. Under standard assay conditions, the incorporation rate remained constant for at least 6 h at 30 degrees C. Transmethylation was not stimulated by KCl nor NaCl. Divalent cations were strong inhibitors. The partially purified enzyme was able to methylate undermethylated poly(A)-rich mRNA isolated from an AdoMet auxotrophic yeast strain briefly exposed to AdoMet-free medium.

Chemical Phenomena↗

PubMed1983

Age-related functional alteration of mouse liver ribosomes.

The in vitro functional capacity of the mouse liver protein synthesis machinery was studied as a function of age. Polysomes from young (one-three months old) and old (18-24 months old) C57BL/6J mice were incubated under standard conditions in a ribosome-free reticulocyte lysate containing [3H]-leucine. The incorporation of radioactivity into hot TCA-insoluble material was measured as a function of time and kinetic curves were compared. A drastic age-related decrease in the initial rate of leucine incorporation was observed when the total ribosomal fraction (containing the whole range of ribosomal aggregates including subunits and single ribosomes) was assayed. When "heavy polysomes" (fractions from which subunits and single ribosomes had been excluded) were compared, the same difference was observed. This latter result indicated that the observed alteration may be attributed to actively translating ribosomes. Results from experiments using inhibitors of initiation suggest that the observed age-related alteration can be attributed to a reduced capacity of ribosomes from older animals to sustain reinitiation.

Aging↗

PubMed1982

Functional properties of rat liver protein synthesizing machinery in relation to aging.

It is well established (van Bezooijen et al., 1977a) that the protein synthesis by isolated liver parenchymal cells (ILPC) from Wag/Rij rats is dependent in a characteristic way on the age of the donor. Whereas cells of middle-aged animals exhibit a decrease in proteo-synthesis activity under in vitro incubation conditions as compared to cells of young rats, a marked increase is observed between 24 and 36 months of age. To investigate whether this overall age-related variation is directly correlated with an intrinsic change at the level of the protein synthesis apparatus of hepatic cells, we compared the size distribution and the in vitro translational activity of polysomes from four age groups. We show that both exhibit the same biphasic response to aging as does the protein synthesizing capacity of ILPC.

Aging↗

PubMed1979

Ethanol metabolism in Drosophila melanogaster.

A quantitative study of the transformation of ethanol into acetaldehyde shows that, in Drosophila melanogaster, the mitochondrial ethanol oxidizing system is not very active but that the part played by catalase appears more important than expected. For a strain without alcoholdehydrogenase, ethanol is highly toxic. The presence of acetaldehyde in the culture medium is toxic for all the strains studied. But, since even a strain without any aldehydeoxidase lives normally, the metabolic production of acetaldehyde does not seem dangerous.

Acetaldehyde↗

PubMed1979