Accumulation of cells with 4N DNA content at nonpermissive temperature in rat embryo diploid cells transformed by tsA mutant of simian virus 40

Abstract

Primary rat embryo cells were transformed by a tsA mutant (tsA640) of simian virus 40 (SV40). Proliferation of all four independent diploid transformants was suppressed at a nonpermissive temperature (40.3 degrees C), being accompanied by a marked increase in the fraction of cells with a 4N DNA content (a 4N peak in the flow cytofluorogram). However, in this case, the fraction of cells with a 2N DNA content (a 2N peak in the flow cytofluorogram) was preserved. Both effects (suppression of proliferation and increase in the 4N peak) diminished when transformed cells were superinfected with wild-type SV40. The increased 4N peak was preserved, albeit not completely, for at least 24 hours, when cells were further incubated in the presence of hydroxyurea at the nonpermissive temperature. On the other hand, the preserved 2N peak all but disappeared within 24 hours, when cells were further incubated in the presence of colcemid at the nonpermissive temperature. These results suggest that the thermolabile large T antigen of SV40 directly or indirectly induces an accumulation of cells with a 4N DNA content, at the nonpermissive temperature, by prolonging the G2 (and/or late S) period.

Simian virus 40 large T-antigen function is required for induction of tetraploid DNA content during lytic infection

“…(C and D) Summary of the average values of gated populations from duplicate samples for each time point illustrated in panel B. Listed are the percentages of the positive populations in the Gl, G2, and >G2 phases (C) and the 14,18,22, and 26 h p.i., cells were fixed and processed for analysis of DNA and T-antigen content by FCM. Gates were placed on the T-antigen-positive G1 and G2 cells.…”

Temperature Dependence in Proliferation of Tetraploid Meth-A Cells in Comparison with the Parent Diploid Cells.

“…A variety of types of cell cycle responses at high temperatures were reported, such as G 1 /G 0 (Tanonaka et al, 1986) and G2/M (Okuda et al, 1986) accumulations. Diploid and tetraploid Meth-A cells responded as accumulation in the late S phases at high temperatures, meaning a low transit rate in the late S phase (Rice et al, 1986).…”