Search PubMed⌕ Search

Biomedical subjects

R Buttyan

Publications and source records attributed to R Buttyan.

112 records · Page 7Linked to original sources
PubMed1981

Factors governing expression of the herpes simplex virus gene for thymidine kinase in clonal derivatives of transformed mouse L cells.

The cells used in this study are sublines of a transformed mouse L cell line (designated H2) that carries the herpes simplex virus (HSV) gene for thymidine kinase (tk) as well as other viral genetic information acquired after exposure of the parental Ltk(-) cells to UV-irradiated HSV type 1. These sublines of the H2 cell line were isolated by cloning under nonselective conditions and were shown to express widely different levels of viral tk. Selective media were used to isolate phenotypically tk(-) and tk(+) variants in sequence from one of the clonal derivatives. As previously reported, superinfection of the tk(+) cell lines with tk(-) HSV type 1 resulted in enhancement of tk activity. A new finding was that viral tk activity could be induced by superinfection in at least 30% of cells from the phenotypically tk(-) sublines, indicating that a functional viral tk gene was retained in a significant proportion of the cells. Experiments were designed to test for the presence of regulatory factors that could influence tk expression in the nonsuperinfected sublines of H2. Absence of freely diffusible regulatory factors was indicated by the finding that the fusion of phenotypically tk(-) and tk(+) cells and untransformed cells in appropriate combinations did not affect the levels of tk detected. Moreover, there was no evidence for the presence in phenotypically tk(+) transformed cells of HSV-specific regulatory factors that could influence expression of tk from a superinfecting viral genome. Phenotypically tk(+) sublines of H2 were found to differ from the phenotypically tk(-) sublines and from untransformed cells in that the tk(+) cells synthesized viral proteins earlier and produced greater yields of infectious HSV progeny after superinfection with wild-type tk(+) virus. We can conclude that the absence of tk expression in the tk(-) H2 sublines cannot be accounted for by rearrangements or loss of DNA sequences encoding the enzyme itself or of sequences necessary for induction of the gene by superinfecting HSV. Moreover, it appears that the expression of tk in the tk(+) H2 sublines correlates with the presence of some factor that can enhance (or the absence of some factor that can depress) HSV replication and gene expression.

Animals↗
PubMed1976

Herpes simplex virus gene expression in transformed cells. I. Regulation of the viral thymidine kinase gene in transformed L cells by products of superinfecting virus.

In this paper we show that the expression of the herpes simplex virus type 1 (HSV-1) gene for thymidine kinase (tk) in HSV-transformed cells is subject to regulation by two viral products synthesized during productive infection of these cells with a tk- mutant of HSV-1. The cell line used in this study is a derivative of tk-deficient mouse L cells that, after exposure to UV-inactivated HSV-1, had acquired the HSV-1 gene for tk (which we term a resident viral gene) and consequently expressed the tk+ phenotype (LVtk+ cells). Productive infection of these cells with HSV-1(tk-) at appropriate multiplicities caused significant enhancement of the viral tk activity. The results of several experiments allow us to conclude that this enhancement was due to increased synthesis of tk specified by the HSV-1 gene resident in the LVtk+ cells and that a specific protein made early after infection with HSV-1(tk-) mediated the enhancement, probably by increasing the production of mRNA from the viral tk gene resident in the LVtk+ cells. Our data also indicate that another HSV-1(tk-) product acted to turn off tk synthesis. The finding that tk activity continued to increase for a longer time after infection of the LVtk+ cells at 2 PFU/cell than after infection at higher multiplicities suggested the synthesis of a product which inhibited tk synthesis and whose concentration reached critical levels earlier at higher multiplicities of infection. Inhibition of DNA synthesis after infection, a treatment that depresses the synthesis of late viral proteins, prolonged the synthesis of tk in LVtk+ cells infected at either 2 or 5 PFU/cell. Infection of the LVtk+ cells with HSV-2(tk-) resulted in only small increases in tk activity, indicating some type specificity in recognition of viral products that can modify the expression of the HSV-1 tk gene resident in these cells.

Cell Transformation, Neoplastic↗
PubMedDate not supplied

Development of a hammerhead ribozyme against BCL-2. II. Ribozyme treatment sensitizes hormone-resistant prostate cancer cells to apoptotic agents.

BACKGROUND: Several lines of evidence strongly implicate a crucial role for the apoptosis suppressing bcl-2 oncogene in the genesis of hormone-refractory human prostate cancer. By efficiently destroying the intracellular bcl-2 mRNA, one might be able to make the prostate cancer cell responsive again to conventional apoptotic stimuli such as androgen withdrawal. To achieve this end, we have devised a catalytic antisense RNA strategy (Ribozyme) for bcl-2 and evaluated its gene therapeutic potential. METHODS AND RESULTS: Bcl-2 overexpressing LNCaP prostatic carcinoma cells (LNCaP/bcl-2) were transfected with the anti-bcl-2 ribozyme RNA using a polyamine-based transfection reagent and the reduction in the intracellular bcl-2 mRNA levels was followed by a ribonuclease protection assay. Using a cell viability assay, prior ribozyme transfection and subsequent application of apoptotic stimuli such as serum starvation or phorbol ester treatment caused a 30% increase in cell death by apoptosis than with these apoptotic stimuli alone. CONCLUSIONS: The results obtained strongly support the ability of a potential anti-bcl-2 ribozyme therapy to synergize with other agents in inducing apoptosis of hormone-resistant human prostate cancer cells.

Apoptosis↗