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V Zaslavsky

Publications and source records attributed to V Zaslavsky.

11 recordsLinked to original sources
PubMed1990

A possible approach to enrich cDNA yields with full-length molecules.

Newcastle disease virus (NDV)-specific hemagglutinin-neuraminidase (HN) mRNAs were used as the model templates for cDNA synthesis. Polyadenylated RNAs were isolated from the particulate fraction of cytoplasmic extracts of NDV-infected cells rather than from nonfractionated extracts. The approach is based on earlier findings that eucaryotic mRNAs are present in cytoplasmic extracts in the form of ribonucleoproteins (mRNPs) rather than as free nucleic acids. The idea of the approach was to separate mRNPs from cell sap RNases prior to RNA extraction in order to minimize partial enzymatic hydrolysis of mRNAs. The presence of the 5' terminus (mRNA sense) in cDNAs synthesized was considered as an indication for the suitability of mRNA templates for cDNA synthesis. The cDNAs were synthesized and cloned in lambda gt10 phage. About 300 phages carrying the HN-specific inserts have been identified among 50,000 recombinants, and nine of them were analyzed for the presence of the HN 5' terminus. It was found that the termini are present in all the clones analyzed. The result is in an agreement with the expectation that removal of cell sap prior to RNA extraction significantly increases the suitability of RNA templates for cDNA synthesis.

Animals↗
PubMed1986

Host involvement in vaccinia virus replication.

Nutrient-depleted conditions, which induced an inhibited state in uninfected cell monolayers, rendered the cells nonpermissive for vaccinia virus, while not affecting their ability to support propagation of an unrelated mengovirus. When the inhibited state was reversed, the ability to propagate vaccinia virus was restored. The inhibited cells retained the ability to support some early-induced events (thymidine kinase synthesis and its arrest, which are DNA synthesis-independent functions in a mouse cell host), but lost the ability to support some others (sensitization of input viral DNA to DNase, induction of DNA polymerase synthesis, and virus-induced CPE). The data are consistent with involvement of a host factor(s) in induction of early vaccinia virus-induced events in infected cells.

Animals↗
PubMed1985

Uncoating of vaccinia virus.

Input vaccinia virus deoxyribonucleoproteids with buoyant densities (in CsCl) very similar (if not identical) to those of viral cores have been found in large cytoplasmic structures in which viral DNA replication takes place. The deoxyribonucleoproteids consist of at least five major and two minor core proteins and viral DNA which is protected against DNase digestion. It is suggested that viral core-like deoxyribonucleoproteids rather than released DNA are used in vaccinia-infected cells both for delayed-early gene transcription and viral DNA replication.

Animals↗
PubMed1982

Evidence for non-chromosomal hepatitis B virus surface (HBsAg)- and core antigen (HBcAg)-specific DNA sequences in a hepatoma cell line.

As demonstrated previously, a "beta particle" fraction isolated from the cytoplasm of PLC/PRF/5 cells contains hepatitis B virus (HBV)-specific DNA. Here, further evidence is provided that the specificity of the DNA for HBV is represented at least by sequences coding for the surface and core antigen (HBsAg and HBcAg). This was shown by two different hybridization techniques. One of them, the technique of Southern, distinguished these hybrid molecules formed from those containing HBV DNA integrated into chromosomes. The HBV-specific beta particle DNA forms two distinct bands separate from the high molecular weight cellular DNA.

Base Sequence↗
PubMed1980

Hepatitis B virus (HBV)-specific structures found in cytoplasmic extracts of cells producing HBV surface antigen (HBsAg) in vitro.

Two kinds of hepatitis B virus-specific particles are present in cytoplasmic extracts of hepatoma cells synthesizing hepatitis B virus (HBV) surface antigen. One class of particle contains the surface antigen of the virus, is 20S in size and has a buoyant density (in CsCl) of 1.2 g/ml. The second class of particle is a deoxyribonucleoprotein (CNP) with 1.3 g/ml buoyant density (in CsCl) and is 30S in size, the DNA of which contains HBV sequences thus proving virus specificity.

Cytoplasm↗
PubMed1979

Labeling of hepatitis B virus surface antigen (HBsAg) synthesized in a HBsAg-producing hepatoma cell line.

Hepatitis B virus surface antigen (HBsAg) could be studied until recently only by isolating it from the blood of carriers, thus making incorporation of radioactive precursors into this protein(s) impossible. The isolation of a cell line producing HBsAg [Alexander et al, 1978] has eliminated this obstacle. The cell line was therefore used for labeling HBsAg either with 35S-methionine or with 35S-cystine. HBsAg was purified by pelleting the component and by isopycnic centrifugation in CsCl gradients. HBsAg-positive fractions (as determined by solid-phase radioimmunoassay) were isolated from the gradients and analyzed in sodium dodecyl sulfate-containing polyacrylamide gels. It was found that although HBsAg contains substantial amounts of 35S-cystine, very little 35S-methionine was incorporated into this protein. In contrast, both labels were found in other structures having a buoyant density of about 1.3 gm/cm3 in CsCl. It was concluded that HBsAg is very low in methionine, and therefore this amino acid should not be used for labeling HBsAg in cells or in a cell-free system. Analysis of 35S-cystine-labeled HBsAg-positive material (buoyant density about 1.2 gm/cm3 in CsCl) revealed five proteins with molecular weights in the range of 48,000-82,000.

Carcinoma, Hepatocellular↗
PubMed1979

Inhibition of vaccinia virus growth by zinc ions: effects on early RNA and thymidine kinase synthesis.

Accumulation of thymidine kinase activity in vaccinia virus-infected cells was severely inhibited by zinc ions if the drug was added within 1 h postinfection. If added later, zinc ions had no effect on the enzyme synthesis. A fraction of RNA which is normally synthesized in infected cells, was missing from a proper part of the gradient if the cells were treated with zinc ions within 1 h postinfection (as has been shown by cosedimentation of pulse-labeled RNAs in isokinetic gradients). It is suggested that a transcriptional (or posttranscriptional) step is involved in zinc-caused inhibition of vaccinia virus growth.

DNA, Viral↗
PubMed1978

Detection of herpes simplex virus thymidine kinase polypeptides in cells labeled with 35S-methionine.

To investigate the size of herpes simplex virus (HSV) thymidine kinase (TK) polypeptides, procedures have been devised to purify the enzyme from infected cells labeled with 35S-methionine by (i) affinity chromatography on Sepharose-5'-amino-5'-deoxythymidine; (ii) preparative isoelectric focusing or preparative PAGE; and (iii) glycerol gradient centrifugation. Portions of enzyme fractions, at each purification step, were also treated with an immunoadsorbent, Sepharose-anti-HSV-1 TK immunoglobulin (IgG). Labeled polypeptides eluted from the immunoadsorbent were analyzed by electrophoresis in SDS slab gels and autoradiography. The results demonstrate that the molecular weights of HSV TK polypeptides are about 40,000. TK-negative HSV-1 mutant B2006 failed to induce the 40 K dalton polypeptide.

Cell Line↗
PubMed1975

Control of thymidine kinase synthesis in IHD vaccinia virus-infected thymidine kinase-deficient LM cells.

The synthesis of vaccinia virus-induced thymidine kinase is normally arrested several hours after infection. In thymidine kinase-deficient LM cells infected with IHD strain of vaccinia virus, arrest occurs whether or not viral DNA synthesis is inhibited. With virus inactivated by UV irradiation, enzyme synthesis takes place, but arrest is abolished. It is suggested that an early viral genetic function is responsible for the cessation of thymidine kinase synthesis.

Animals↗