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Biomedical subjects

H Soreq

Publications and source records attributed to H Soreq.

At least 163 records · Page 9Linked to original sources
PubMed1982

Degranulation of rat cerebellum induces selective variations in gene expression.

Selective variations in the composition of poly(A)-containing mRNA were found to be induced in the rat cerebellum by X-irradiation. mRNA populations prepared from normal and X-irradiated rat cerebella at different stages of their development displayed equal efficiencies when translated in vitro in reticulocyte lysates. Specific differences were revealed, however, when the labeled translation products of both mRNA preparations were subjected to two-dimensional gel electrophoresis followed by fluorography of the dried gels. Of more than 100 polypeptide products, several showed marked intensity differences, indicating changes in the abundance of their directing mRNA species. These differences appear both in developing and in mature cerebellar mRNA, and the extent of modification in mRNA is much higher than the consequent changes in the composition of proteins in the irradiated cerebellum. The degranulation-induced modifications in levels of specific cerebellar mRNA species can be used to identify proteins whose biosynthesis depends on the presence of interneurons.

Animals↗
PubMed1981

Microinjected Xenopus oocytes synthesize active human plasminogen activator.

Induction of synthesis of the protease plasminogen activator (PA) by hormones, oncogenic viruses and tumor promoters occurs at the transcription level. A novel bioassay for PA messenger RNA was developed to study the regulation of PA synthesis and the genetic elements involved in it. Poly(A)-containing RNA from HEp-3, a PA-rich tumor of human origin, was found to direct the synthesis of a new proteolytic activity when microinjected into Xenopus oocytes. Newly synthesized protease can be detected within a few hours after microinjection of minute quantities of unfractionated mRNA. The new enzymatic activity is indistinguishable from human PA: it is absolutely dependent on human plasminogen; it is neutralized by serum raised against urokinase, the human urinary PA; and it comigrates with urokinase and HEp-3 PA in gel electrophoresis, exhibiting a molecular weight of 60,000.

Animals↗
PubMed1981

Plasminogen activator in the rodent brain.

The cellular origin(s), the biochemical properties and the developmental pattern of the protease plasminogen activator (PA) were investigated in the rodent brain. PA activity was localized in frozen brain sections by a novel autoradiography technique. PA levels and electrophoretic mobility were determined in homogenates prepared from major regions of the developing and the mature brain, and both the localization and the specific activity of the enzyme were examined in X-irradiated brain regions. PA activity was shown to be correlated with cell bodies in neuronal-enriched regions and also with endothelial, meningeal and ependymal layers. PA levels increased in a transient manner and at different rates and time periods in the various brain regions that were analyzed. PA in neuronal, but not in epithelial cell layers was affected by X-irradiation and one of the brain PA species had a similar molecular weight of that of neuroblastoma cells. Our findings suggest that in the brain PA is produced by neurons and by epithelial cells, and that it may have additional functions to that of thrombolysis both in the developing and the mature brain.

Aging↗
PubMed1981

Translational activity and functional stability of human fibroblast beta 1 and beta 2 interferon mRNAs lacking 3'-terminal RNA sequences.

Polyadenylylated mRNA was purified from poly(I).poly(C)- and cycloheximide-superinduced human fibroblast (FS-4) cultures. The mRNA was subjected to electrophoresis through an agarose/CH3HgOH gel, and human fibroblast beta 1 and beta 2 interferon mRNAs were isolated. Each mRNA preparation was phosphorolyzed at 0 degrees C for 20 min by using a molar excess of polynucleotide phosphorylase to produce RNAs lacking poly(A) and then incubated at 37 degrees C for varying lengths of time to allow the phosphorylase to further digest the deadenylylated RNA from the 3' end in a processive and synchronous manner. Removal of the poly(A) (less than or equal to 100 residues) and approximately 100 adjacent residues from human fibroblast beta 1 interferon mRNA (native length, 900 residues, including a 3'-noncoding region of 203 residues) did not alter the translational activity or the functional stability of this mRNA in Xenopus oocytes, whereas deletion of the poly(A) and approximately 200 adjacent residues decreased its translational efficiency. On the other hand, removal of the poly(A) (approximately 200 residues) and approximately 200 adjacent residues from human fibroblast beta 2 interferon mRNA (native length, 1300 residues) did not alter the translational activity or the functional stability of this molecule in oocytes. Thus, neither the poly(A) nor large segments of the 3'-noncoding region (which includes the hexanucleotide A-A-U-A-A-A sequence, at least in the case of beta 1 mRNA) are required for the maintenance of the functional stability of human beta 1 and beta 2 interferon mRNAs in Xenopus oocytes.

Animals↗
PubMed1980

Two interferon mRNAs in human fibroblasts: in vitro translation and Escherichia coli cloning studies.

Two mRNA species that produce biologically active interferon were isolated from human fibroblasts and studied by size fractionation and cloning in Escherichia coli plasmid pBR322. The major fibroblast interferon (Hu IFN-beta 1) is coded for by the smaller of the two mRNAs, an 11S species, 900 nucleotides long, which in cell-free systems yields a 20,000 Mr protein. The second interferon mRNA species (Hu IFN-beta 2) is 14S, about 1300 nucleotides long, and codes for another protein of 23,000-26,000 Mr. The two interferon mRNAs do not cross-hybridize. Both are induced by poly(rI.rC), but IFN-beta 2 mRNA is induced to about 10% in cells by cycloheximide treatment alone whereas under these conditions IFN-beta 1 is not induced.

Biological Assay↗
PubMed1979

Rat growth hormone gene: intervening sequences separate the mRNA regions.

Rat genomic DNA was digested with various restriction endonucleases, separated by gel electrophoresis and hybridized to 125 I-labeled mRNA for the precursor protein to growth hormone. Restriction sites were found within the genomic DNA that were not found in the previously reported DNA sequence corresponding to the mRNA (19). It appears that the gene for growth hormone contains intervening sequences separating the DNA regions that specify mRNA sequences.

Animals↗
PubMed1978

Does 3'-terminal poly(A) stabilize human fibroblast interferon mRNA in oocytes of Xenopus laevis?

Polynucleotide phosphorylase (polyribonucleotide:orthophosphate nucleotidyltransferase, EC 2.7.7.8) purified from Escherichia coli was used enzymatically to deadenylate polyadenylated human fibroblast interferon mRNA preparations obtained from human diploid fibroblasts (FS-4 strain) induced by poly(I)-poly(C) (20 microgram/ml) in the presence of cycloheximide (50 microgram/ml, 4 hr). Both the polyadenylated and the deadenylated interferon mRNA preparations were translated into biologically active human interferon when injected into oocytes of Xenopus laevis. In the oocytes the functional stability of deadenylated interferon mRNA was indistinguishable from that of polyadenylated interferon mRNA.

Animals↗
PubMed1977

Purification and characterization of polynucleotide phosphorylase from Escherichia coli. Probe for the analysis of 3' sequences of RNA.

A simple procedure for purifying polynucleotide phosphorylase from Escherichia coli cells by means of affinity chromatography on an RNA-Sepharose column is described. The purified enzyme preparation has a specific activity 3500-fold that of the crude extract and is essentially homogeneous, as determined by ultracentrifugation, polyacrylamide gel electrophoresis under denaturing conditions, isoelectric focusing and serological assays. It is virtually free of nuclease contamination, a property which permits its use in the synchronous phosphorolysis of RNA chains. The enzyme molecule is composed of three identical subunits of Mr = 84,000. Each subunit contains three cysteine residues, one of which reacts with 5,5'-dithiobis(2-nitrobenzoic acid) whereas the two other groups are only exposed on denaturation of the protein. All three enzyme subunits participate in the processive phosphorolysis of the poly(A) tail of each globin mRNA chain. An advantageous method was developed for synchronous phosphorolysis of RNA molecules using a molar excess of polynucleotide phosphorylase immobilized onto Sepharose.

Chromatography, Affinity↗
PubMed1977

Initiation of RNA synthesis in isolated nuclei.

Ribonucleotide triphosphates, labeled at the beta position, were synthesized and used directly to quantify RNA chain initiation in nuclei isolated from Friend cells grown in tissue culture. At the optimal salt concentration, low-molecular-weight RNAs (4-5 S) synthesized by RNA polymerase III were the predominant species initiated. Less than 5% of the molecules were initiated by polymerase II. We calculate that 50-80% of the small RNA molecules synthesized in vitro were also initiated in vitro. Assuming that a substantial fraction of the nuclei were active in vitro, the number of 4-5 S RNA molecules initiated per nucleus was about 100 molecules/min.

Acetates↗
PubMed1977

Membrane associated cytoplasmic mRNA in Artemia salina; functional and physical changes during development.

The physical and functional properties of the mRNA population from developing embryos of the brine shrimp Artemia salina were characterized. About 20% of the total poly(A)-rich mRNA in these embryos appears to be specifically associated with the membrane fraction throughout early development, and physically differs markedly from the free cytoplasmic mRNA. The membrane-associated mRNA fraction consists of two well-defined populations of molecular weight of 5.2x10(5) and 3.6x10(5), whose relative amount changes during the various stages of embryo development. The size of the poly(A) tail at the 3'-end of the mRNA molecules, as estimated by processive phosphorolysis, was found to consist of 180 and 210 adenosine residues for the two respective mRNA species. The in vitro translation products of the membrane-bound mRNA molecules are apparently similar to those of the free mRNA molecules.

Animals↗