Induction of HL-60 cells to undergo apoptosis is determined by high levels of wild-type p53 protein whereas differentiation of the cells is mediated by lower p53 levels.

The observation that wild-type p53 may induce cells to undergo either apoptosis or differentiation raises the question of whether these two events share similar p53-dependent pathways. To evaluate the interrelationship between these two p53-dependent processes, our study focused on the human HL-60, a promyelocytic p53 nonproducer cell line in which p53 expression was introduced and the induction of apoptosis and differentiation was followed under controlled conditions. p53 expression was induced in the HL-60 cell line by infection with the recombinant wild-type p53 (p53WT) vaccinia virus.

Inhibition of human immunodeficiency virus by N-methylisatin-beta 4':4'-diethylthiosemicarbazone and N-allylisatin-beta-4':4'-diallythiosemicarbazone.

N-methylisatin-beta 4':4'-diethylthiosemicarbazone(M-IBDET) and N-allylisatin-beta-4':4'-diallylthiosemicarbazone(A-IBDAT ) inhibit the production of Human Immunodeficiency virus (HIV). Virus inhibition was related to the thiosemicarbazone derivative (TSCD) concentrations and time of treatment. Inhibition of HIV production was confirmed by various parameters of virus assay employing reverse transcriptase activity, plaque forming units (PFU) and levels of viral structural proteins.

Transformation, growth rate, and the heme biosynthetic pathway in V-abl-transfected fibroblasts.

The relationship between growth rate and various parameters of the heme biosynthetic pathway was studied in two cell lines of rat fibroblasts (REabl-1 and REabl-3) transfected with v-abl oncogene, coded by the Abelson murine leukemia virus, and subjected to glucocorticoid dependent transformation. In the REabl-1 cell line, whose growth rate was only slightly affected by dexamethasone (DX), almost no change was noticed either in heme content or in the enzymatic activities of aminolevulinate synthase (ALAS), porphobilinogen deaminase (PBGD), and ferrochelatase (FC) in the presence of various concentrations of DX. In the REabl-3 cell line, exhibiting a growth rate highly sensitive to DX, a significant reduction in intracellular heme concomitantly with decreases in ALAS and FC activities and a threefold increase in PBGD were noted.

Relationships between structure and antiretroviral activity of thiosemicarbazone derivatives.

In an attempt to develop anti-AIDS drugs, the compound isatin beta-thiosemicarbazone has been subjected to systematic structural modifications. The resulting synthesized thiosemicarbazone derivatives (TSCDs) were examined for their ability to act as antiretrovirus agents in a model system--2M3/M cell system--consisting of B lymphocytes transformed by the v-abl oncogene and chronically infected with a retrovirus, the Moloney leukemia virus (M-MuLV). The efficacy of the synthesized TSCDs against retroviruses was determined by assaying the therapeutic index (TI) values of the compounds.

Selective repression of v-abl-encoded protein by N-methylisatin-beta-4',4'-diethylthiosemicarbazone and N-allylisatin-beta-4',4'-diallylthiosemicarbazone.

N-Methylisatin-beta-4',4'-diethylthiosemicarbazone (M-IBDET) and N-allylisatin-beta-4',4'-diallylthiosemicarbazone (A-IBDAT) selectively inhibited v-abl protein (P120), an oncogene product associated with tyrosine kinase activity. Concentrations of M-IBDET ranging between 0.17 and 0.

Expression of wild-type and mutant p53 proteins by recombinant vaccinia viruses.

To facilitate the purification of wild type p53 protein, we established a recombinant p53 vaccinia viral expression system. Using this efficient eukaryotic expression vector, we found that the expressed p53 proteins retained their specific structural characteristics. A comparison between wild type and mutant p53 proteins showed the conservation of the typical subcellular localization and the expression of specific antigenic determinants.

Accelerated heme synthesis and degradation in transformed fibroblasts.

Various parameters of the heme biosynthetic pathway were studied in two cell lines, one nontransformed and the other malignantly transformed (MLV/MS), both replicating at the same rate. Using the above system enabled us to distinguish between phenomena characteristic of the malignant transformation per se and those due to accelerated growth rate. Heme synthesis and degradation as well as the activities of ALAS, ALAD, PBGD, and FC were found to be increased in the transformed cells.

Growth rate determines activity of porphobilinogen deaminase both in nonmalignant and malignant cell lines.

PBGD activity and growth rate were determined in cultures of rat embryo fibroblasts, nontransformed and MLV/MS transformed fibroblastic cell lines; NIH-3T3 cells, and in a mouse lymphosarcoma cell line [L-929]. The two parameters examined correlate positively (P less than 0.001).

N-methylisatin-beta-4',4'-diethylthiosemicarbazone, an inhibitor of Moloney leukemia virus protein production: characterization and in vitro translation of viral mRNA.

The mode of inhibition of N-methylisatin-beta-4',4'-diethylthiosemicarbazone (M-IBDET) on Moloney leukemia virus production was studied. Drug treatment of infected cells did not alter the amounts or sizes of the 35S and 22S subgenomic viral RNAs. The translation abilities of poly(A)+ RNA derived from M-IBDET-treated cells was also unaffected, as judged by cell-free translation analysis.

Effect of N-methylisatin-beta-4':4'-diethylthiosemicarbazone on intracellular Moloney leukemia virus constituents.

N-Methylisatin-beta-4':4'-diethylthiosemicarbazone (M-IBDET) inhibits intracellular production of viral constituents in a mouse cell line, 3T3/MLV, chronically infected with Moloney leukemia virus. Electron microscopic observations confirmed that inhibition of virus production by the drug was not associated with any structural changes in the cell morphology or any damage to the plasma membrane, the site of viral assembly and 'budding'. Treatment of the cells with 17 microM M-IBDET for 6 h inhibited extracellular virus production by 80% but did not affect the level of viral RNA in the cytoplasm or in the plasma membrane.

Studies on cell binding and internalization of human lymphoblastoid (Namalva) interferon.

The binding of iodinated human lymphoblastoid Namalva interferon to Namalva cells, to a human fibroblast cell strain (FS11), and to a bovine kidney cell line (MDBK) was characterized. Scatchard analysis of the binding data indicated the presence of about 1000-2000 receptors per cell and dissociation constants of the order of 0.1 to 0.

Inhibition of the synthesis of Moloney leukemia virus structural proteins by N-methylisatin-beta-4',4'-diethylthiosemicarbazone.

The mechanism of inhibition of Moloney leukemia virus by N-methylisatin-beta-4',4'-diethylthiosemicarbazone was studied. Experiments that used [3H]leucine for short-pulse labeling in the presence of the drug resulted in a 71% inhibition in the synthesis of Pr-80, the polypeptide precursor of the gag viral proteins. The radioactive pulse products of the polypeptide precursors after a further 2-h chase period showed a normal cleavage of the precursors, with the formation of a reduced amount of final mature viral structural proteins.

Glycoprotein enrichment in Moloney leukemia virus structural proteins released from interferon-treated cells.

Interferon treatment of Moloney-leukemia-virus-infected cells (3T3/MLV) leads to the formation of virus particles enriched with viral structural glycoproteins, in addition to the inhibition of virus production. A preferential inhibitory effect on incorporation of RNA and proteins rather than glycoproteins was found in the released virus particles from interferon-treated cells. Enrichment in 70,000- and 45,000-dalton glycoprotein (gP-70, gP-45) in these particles was further demonstrated by polyacrylamide analysis of viral proteins pulse-labeled with [3H]-leucine.

Localization of reverse-transcriptase in interferon-treated mouse cells chronically infected with Moloney leukemia virus.

Interferon treatment of mouse cells chronically infected with Moloney leukemia virus (3T3/MLV) resulted in 97 per cent inhibition of infective virus release. The intracellular localization and distribution of virus reverse-transcriptase and group specific (gs) antigen were determined in interferon treated and control cells. Cytoplasm of infected cells was fractionated by isopycnic centrifugation on discontinuous sucrose gradients.

Inhibition of Moloney leukaemia virus production by N-methylisatin-beta-4':4-diethylthiosemicarbazone.

N-methylisatin-beta-4':4'-diethylthiosemicarbazone (M-IBDET) inhibited the production of Moloney leukaemia virus (MLV). Virus inhibition was related to drug concentrations and time of treatment. The effective antiviral drug concentrations ranged between 3.