DNA of simian virus 40 mutates Chinese hamster cells

Abstract

Infection of Chinese hamster cells with SV 40 DNA gives rise to mutants resistant both to S-axaguanine (AG) and aminopterin (AP). This mutagenic effect can be raised when facilitating DNA uptake of cells by a helper agent. The extent of muyagenic action depends further on the concentration of DNA applied to the cells, with 2 micrograms/ml being more effective than 10 micrograms/ml, as well as on the period of incubation of infected cells before onset of mutant selection (mutation expression time). Using the AG resistance marker the mutation frequency can be increased more than 8-fold compared with the spontaneous mutation frequency. Reconstituted SV 40 minichromosomes show a mutagenic action which is similar to the DNA-mediated mutagensis whereas non-viral DNA from mammalian cells fails to induce mutations significantly. A major part of isolated clones of SV 40-induced mutants tested so far does express SV 40 T-antigen, suggesting the persistence of SV 40 genetic material in these clones. The possible existence of relations between mutagenic and transforming capacities of SV 40 is discussed.

Simian Virus 40-induced Mutagenesis: Action of the Early Viral Region

“…In their experiments they used a m.o.i, of 10 p.f.u./cell, sufficient to transform these cells. Conceivably, these conditions of infection were not suited for the production of significant effects (see Theile et at., 1980a).…”

“…Besides the V79 TG resistance system, further selection systems were applied in this experiment to obtain additional information. As is shown in (Renkawitz et al, 1982) Four nucleotides deleted within the BglI site (ort-mutant) Early viral region lacking only one of the two 72 bp enhancer elements * sv40 DNA was prepared as described earlier (Theile et al, 1980a), Plasmids, after transfection into Escherichia eoli, were amplified, purified and DNAs were extracted (Maniatis et al, 1982). the assumption that SV40-induced mutagenesis depends on the expression of the early region.…”

Relationship of simian virus 40 tumor antigens to virus-induced mutagenesis.

“…This hypothesis has been tested in several laboratories (6,(23)(24)(25)(26)(27), but the evidence so far remains inconclusive (13). After SV40 infection, the frequency of somatic mutants increased 2-to 4-fold over the spontaneous frequency in uninfected control cells in most studies (5, 12; S. Lavi, personal communication), but an increase of almost 10-fold has been reported by one group (26,27).…”

“…In an attempt to clarify this discrepancy, we analyzed the effect of various SV40 mutants on the induction of mutation both after acute infection and in stably transformed lines. It has been reported that a functional A gene is required for SV40-induced mutagenesis (25,27). We are unable to corroborate this finding after acute infection of nontransformed cells.…”

“…A number of studies have shown that SV40 infection of nonpermissive and semipermissive cell lines results in chromosomal changes, such as polyploidization (7,8) and chromosomal breaks and rearrangements (8,12,29), and in somatic mutations at different loci (12,24,25,27,28). The observation that some cells transformed by SV40 have altered karyotypes (9,29) led to the suggestion that polyploidization may be involved in the process of malignant transformation (9).…”