Ultrastructural localization of cytomegalovirus DNA synthesis in infected guinea-pig cells.

Using electron microscopic autoradiographic techniques, the uptake of [methyl-3H] thymidine into uninfected and guinea-pig cytomegalovirus (GPCMV)-infected guinea-pig embryo (GPE) fibroblast cells was investigated. In GPCMV-infected GPE cells, [methyl-3H]thymidine uptake into cellular DNA was inhibited prior to the onset of virus DNA synthesis as well as during the entire period of virus replication. Virus DNA synthesis increased slowly during the period of active virus replication, which usually lasted from 18 to 48 h post-infection. Only the electron-dense amorphous matrices and fibrillar structures in the nuclear inclusions were associated with the tritiated labels and thus contained virus DNA.