DYNAMIC ORGANIZATION OF DNA-REPLICATION IN ONE-CELL MOUSE EMBRYOS - RELATIONSHIP TO TRANSCRIPTIONAL ACTIVATION

We have analyzed the spatial and temporal relationship between transcr iption and replication sites during the first cell cycle in mouse embr yos. Embryos were microinjected with both 5-bromouridine-5'-triphospha te and digoxygenin-11-deoxyuridine-5'-triphosphate to visualize transc ription and replication sites respectively. We detected six different phases of replication during S phase and dated the onset of zygotic tr anscription at the end of the S phase. Using confocal microscopy, we s howed that there is essentially no colocalization of replication and t ranscription sites at this stage of development. Moreover, studies on aphidicolin-treated embryos demonstrated that inhibition of DNA replic ation does not hinder transcriptional activation at the 1-cell stage. (C) 1997 Academic Press.