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Biomedical subjects

J Shlomai

Publications and source records attributed to J Shlomai.

46 records · Page 3Linked to original sources
PubMed1977

Electron microscopy of herpes simplex virus DNA molecules isolated from infected cells by centrifugation in CsCl density gradients.

Herpes simplex virus (HSV) DNA molecules were isolated from infected BSC 1 cells and centrifuged in CsCl-ethidium bromide density gradients. Both newly labelled and mature virus DNA molecules were found to have a linear conformation. The morphology of virus DNA molecules at different stages of the virus growth cycle in BSC 1 cells, was studied by electron microscopy after separation of virus DNA from cellular DNA by centrifugation in CsCl gradients. In each sample, about 200 virus DNA molecules were photographed and the different morphological forms were studied. Four classes of virus DNA molecules were observed: (a) mature linear DNA molecules, 52-4 +/- 3-3 micronm in length, (b) DNA intermediates, (c) virus DNA molecules having one or more single-stranded filaments attached to them and (d) molecules with collapsed regions or with branches. A few circular molecules as well as linear DNA molecules longer than unit length were also observed. The virus DNA molecules resembling replicative intermediates gradually increased in number and reached a maximal amount of about 5% of the virus DNA population at 12 h after infection. The other forms of virus DNA were found to persist after the number of replicating DNA molecules decreased.

Cell Line↗
PubMed1977

Replication of herpes simplex virus DNA after removal of hydroxyurea block from infected cells.

Hydroxyurea (HU) treatment of HSV-infected cells markedly inhibits the synthesis of virus DNA. Only 0-3.6 of the 3H-thymidine label was incorporated into virus DNA in the presence of HU as compared to untreated infected cells. Removal of HU resulted in a renewed synthesis of virus DNA as determined by the gradual increase in the incorporation of 3H-thymidine into HSV DNA. The labelled virus DNA molecules were isolated and chromatographed on benzoylated napthoylated DEAE (BND)-cellulose columns to separate the replicative intermediates that have single-stranded (ss) sequences from the mature double-stranded (ds) DNA genomes. Mature radioactive dsDNA molecules were found to appear at 22 min after removal of HU and gradually increased in amount thereafter. The virus DNA molecules synthesized during the initial 20 min after removal of HU, constitute the replicative intermediates of HSV DNA. It was calculated that the synthesis of HSV DNA proceeds at the rate of about 5 X 10(6) daltons per min.

Animals↗
PubMed1977

Phosphonoacetic acid-resistant mutants of herpes simplex virus: effect of phosphonoacetic acid on virus replication and in vitro deoxyribonucleic acid synthesis in isolated nuclei.

Phosphonoacetic acid (PAA) inhibits the replication of herpes simplex virus in BSC-1 cells and the in vitro synthesis of deoxyribonucleic acid (DNA) in isolated nuclei. Phosphonopropionic acid at a concentration of 100 mug/ml had no effect on herpes simplex virus replication. PAA-resistant mutants were obtained at a rate of 1 in 10(4) plaque-forming units after 5-bromodeoxyuridine mutagenization of the virus. These mutants replicate in BSC-1 cells in the presence of 100 mug of PAA per ml and induce a PAA-resistant DNA polymerase that synthesizes DNA in vitro in the presence of PAA.

Acetates↗
PubMed1976

Analysis of herpes simplex virus DNA synthesized in infected nuclei by chromatography on benzoylated naphthoylated DEAE cellulose columns.

The nature of the DNA molecules synthesized in nuclei of herpes simplex virus (HSV)-infected cells in vivo and in vitro was studied by chromatography on BND-cellulose columns after shearing to DNA fragments of 10 to 20 X 10(6) daltons. The incorporation of labelled precursors occurs in the DNA fragments containing single-stranded regions, presumably the replication forks. Prolongation of DNA synthesis leads to the accumulation of labelled DNA fragments that lack single-stranded sequences. Analysis of the isolated DNA fragments by density centrifugation in CSCl gradients revealed that most of the labelled DNA molecules are of virus specificity and the minority are cellular DNA fragments. Double-stranded virus DNA fragments and virus DNA fragments containing single-stranded sequences band in CSCl gradients at a density of 1-718 g/ml, the density of virion DNA. This suggests that the replicating HSV DNA molecules have the same density as the virion DNA and contain relatively little single-stranded DNA. The synthesis of HSV DNA molecules under in vitro conditions in isolated nuclei occurs by incorporation of the precursors into DNA fragments with single-stranded regions. The synthesis of cellular DNA in nuclei from hydroxyurea and cytosine arabinoside treated cells also occurs by elongation of nascent DNA chains.

Arginine↗
PubMed1975

Nucleic acid biosynthesis in nuclei of cell infected with herpesviruses (HSV and EBV).

Analysis of nuclei isolated from herpes simplex virus (HSV)-infected cells by electrophoresis in polyacrylamide gels showed that only virion-associated DNA molecules migrated into the gels. The viral DNA molecules, which do not migrate in the gels, are the precursors for the mature viral DNA. Centrifugation of deoxycholate-treated infected nuclei in sucrose gradients revealed that most of the viral DNA co-sedimented with the cellular DNA. The DNA-dependent RNA polymerase activity also co-sedimented with the viral and cellular DNA. Incubation of nuclei isolated from HSV-infected cells, under in vitro conditions that support DNA synthesis, resulted in the synthesis of viral molecules of low molecular weight. Under the same conditions, nuclei from Burkitt lymphoblasts did not synthesize DNA. The nature of the association between cellular DNA and EBV DNA was studied by hybridization with EBV cRNA. EBV-specific sequences were found in the lymphoblast DNA; they banded at a density of 1.707 g/cm3. Some of the viral mRNA transcribed in HSV-infected nuclei is symmetrically transcribed from HSV DNA. The symmetrical portions of the RNA are removed, since poly (A)-containing mRNA molecules lack homologous sequences. Most of the RNA synthesized in HSV-infected nuclei can be released after incubation of the nuclei in vitro in the presence of ATP. The released RNA consists of poly(A)plus and poly (A)-minus molecules. The mechanism of RNA transport from the nuclei still remains to be studied.

Adenosine Triphosphate↗