This study examined how ultraviolet-inactivated vesicular stomatitis virus (UV-VSV) affects DNA synthesis initiation in cultured chick embryo cells. The researchers synchronized cell populations by replacing culture medium on stationary monolayers, which induced DNA synthesis starting at 4 hours and continuing for 8 hours, with cell division occurring at 15-18 hours. When cells were infected with UV-VSV at the time of medium replacement, the onset of DNA synthesis was blocked, with approximately 70% inhibition of entry into DNA synthesis. However, when cells were infected 6 hours after medium replacement (during S phase), ongoing DNA replication and subsequent cell division proceeded normally. The researchers demonstrated that UV-VSV selectively prevents G1 phase cells from entering S phase, without inhibiting DNA replication once it has begun. This selective inhibition occurs without viral replication, distinguishing it from adenovirus effects on DNA synthesis. The findings suggest UV-inactivated VSV provides a useful model for studying virus-cell interactions and mechanisms of DNA synthesis initiation in animal cells.

Key findings

• UV-inactivated VSV selectively inhibits entry of G1 phase cells into S phase but does not affect ongoing DNA replication once it begins
• Infection at medium replacement (0 hour) prevented DNA synthesis onset and mitosis, while infection at 6 hours (during S phase) allowed normal DNA replication and cell division to proceed
• The inhibitory mechanism is unique compared to adenovirus because it requires neither viral replication nor integration into the nucleus, and does not reduce ongoing DNA replication
• Medium replacement induced synchronized DNA synthesis in approximately 55% of the stationary cell population, with cells entering S phase at 4 hours and completing division by 15-18 hours