A human DNA telomeric fragment contains yeast ARS and mitotic stabilizing sequences.

A minilibrary of human DNA fragments was prepared in the vector YIP5 from a DNA preparation enriched for telomeric sequences. Screening of the library produced one clone that hybridized to the TTAGGG sequence. The cloned DNA fragment was shown to be telomeric by a number of criteria. In situ hybridization to metaphase human chromosomes showed that the fragment hybridized to the tips of all human chromosomes. The fragment contained at least two yeast autonomously replicating sequences (ARS) and stabilizing sequences, since it transformed Saccharomyces cerevisiae with high efficiency, giving rise to clones which were mitotically stable under non-selective growth.

Chromosomal aberrations induced in human cultured cells by liposome-encapsulated deoxyribonuclease I.

Experiments of incorporation of a nucleolytic enzyme into human cells cultured in vitro have been carried out with the aim of inducing structural chromosome variations. Human heteroploid cells, either as asynchronous populations or enriched in mitoses, and PHA-stimulated lymphocytes were used as recipients. We found that all these cells when exposed to pancreatic DNAase I encapsulated in liposomes, either of multilamellar (MLV) or of small unilamellar (SUV) type, show an incidence of chromosome damage higher than that induced by the enzyme free in the incubation buffer. Our results indicate that liposomes are suitable vehicles for the transfer of an exogenous nuclease into human cultured cells. The enzyme remains functionally active and interacts with nuclear DNA, giving rise to chromosome lesions.

Phenolphthalein induces chromosome aberrations in human and Chinese hamster liver cells (CHEL) cultured in vitro.

Phenolphthalein is a nonprescription laxative agent that has been widely used during this century. Recent studies in animal models have shown that phenolphthalein has carcinogenic activity. In order to assess cytogenetic effects on human cells in vitro, we tested phenolphthalein in a chromosome aberration assay in human embryo cells derived from amniotic fluid. Our results show that phenolphthalein induces a significant increase in the frequency of chromosome aberrations in human cells. The lowest dose level at which the clastogenic effect is evident is 23.2 microg/ml. Similar positive results were obtained in a Chinese hamster liver cell line, which is metabolically competent to activate different classes of promutagens and procarcinogens into biologically active metabolites. Instead, parallel experiments in Chinese hamster ovary cells did not show any clastogenic effect due to phenolphthalein. These latter data suggested that phenolphthalein acts as a promutagen and must be metabolically activated to exert its clastogenic effect. Teratogenesis Carcinog. Mutagen. 20:209-217, 2000.

Liposomes induce chromosome aberrations in human cultured cells.

The genotoxic effect of multilamellar lipid vesicles (MLV) was analysed on cultured heteroploid and diploid human cells. Dose-dependent reduction of cell survival and mitotic rate as well as induction of chromosome aberrations were observed. Chromatid and chromosome breaks and chromatid exchanges were found in 24-h culture after liposome treatment, whereas chromosome rearrangements were prevalent at 48 h. Neutral (PC/Chol) and positive (PC/SA) MLV showed a greater damage than negative (PS/PC; PS) MLV. Fibroblasts were the most sensitive cell type. In the case of PC/Chol MLV vesicles, control experiments with PC and Chol of controlled purity ruled out the possibility that the observed chromosome aberrations were caused by toxic oxidation products present in commercial preparations.

Resistance of HSV-1 growth to aphidicolin in two aphidicolin resistant cell lines.

The growth of herpes simplex virus type 1 (HSV-1) was examined in two cell lines resistant to aphidicolin by inhibition of infectious progeny production in the presence of the drug. The results reported show that the virus yield, which was severely inhibited by the drug in sensitive cells, was only slightly inhibited in the resistant cell lines. This suggests that the metabolic alteration known to confer resistance to the cell line (that is the altered deoxyribonucleoside triphosphate pool) may also allow viral growth to proceed in the presence of aphidicolin, and that therefore HSV replication at least partially depends upon the host replicative apparatus.