Effects of reovirus infection on the spatial and temporal organization of DNA replication in L cells.

DNA fiber autoradiography was used to analyze the spatial and temporal organization of activated initiation sites for DNA replication in mouse L929 cells infected with reovirus type 3 (Dearing strain) and in uninfected control cells. Cells were labeled for 10 min with 3H-thymidine at high specific activity followed by 3 h of low specific activity labeling. Reovirus infection causes no change in the rate of replication fork progression, but increases both the mean distance between activated initiation sites by approximately 30% and the nonrandomness in the spatial distribution of the sites along the DNA fibers. Significant synchronization of initiation in adjacent activated sites was detected on DNA fibers from uninfected cells and from reovirus-infected cells. The mean relative initiation time for pairs of initiation events which had occurred prior to high specific activity labeling did not differ significantly between the infected and uninfected cells. The data are consistent with the interpretation that reovirus infection shuts off initiation sites in a coordinated fashion, possibly by preventing activation of entire clusters of potential initiation sites.