Tadashi Yamashita

Induction of DNA synthesis by adenoviruses in contact-inhibited hamster cells

Abstract Highly oncogenic (types 12 and 31), weakly oncogenic (types 3 and 2), and non-oncogenic (types 2 and 5) adenoviruses induced DNA synthesis in contact-inhibited hamster cells. DNAs induced by adenoviruses 2, 7, and 12 in contact-inhibited hamster cells were mainly cellular. High multiplicity of infection was necessary for the induction of DNA synthesis. Adenoviruses 12 and 31 were efficient in the induction of DNA synthesis and the patterns of DNA synthesis induced by these viruses were early and of short duration, whereas adenoviruses 3, 7, 2, and 5 were less efficient in the induction of DNA synthesis and the patterns of DNA synthesis induced by adenoviruses 3 and 7 were late and long-lasting. The patterns of DNA synthesis induced by adenoviruses 2 and 5 were intermediate between these two patterns. Adenoviruses 2 and 5 replicated in hamster cells, and viral DNA detected in DNA induced in hamster cells by adenovirus 2. Adenoviruses 12, 31, 3, and 7 did not replicate in hamster cells and viral DNAs were hardly detected in DNAs induced in hamster cells by adenoviruses 12 and 7.

Suppression of cellular DNA synthesis in growing cells by ultraviolet-irradiated adenoviruses.

Abstract Ultraviolet (UV)-irradiated adenovirus 2 and 12 suppressed cellular DNA synthesis in growing human embryo kidney cells. The analysis of the mechanism of the suppression revealed that RNA and protein syntheses were not suppressed, thymidine kinase and DNA polymerase were produced normally, cellular DNA was not degraded, and the chain-elongation of nascent DNA proceeded normally. The autoradiograms showed that the suppression was due to the decrease in the number of cells synthesizing DNA, not to the decrease in the rate of DNA synthesis in a nucleus. These observations indicated that the initiation of cellular DNA synthesis was suppressed by UV-irradiated adenovirus. The suppressing activity was found in the UV-irradiated complete virion fraction (density 1.34). Quantitative analyses with purified virions revealed that suppression of cellular DNA synthesis was dependent on multiplicity of infection and 10 3 cell-associated virions suppressed 90-80% of cellular DNA synthesis.