Replication of the rat aldolase B locus differs between aldolase B-expressing and non-expressing cells.

We previously reported a rat chromosomal origin of DNA replication (oriA1) that encompassed the aldolase B (AldB) gene promoter. Here, we examined utilization of oriA1 in AldB-expressing and non-expressing cells. The results suggested the occurrence of mutually exclusive regulation between DNA replication and transcription. Nascent strand abundance as assayed by competitive polymerase chain reaction using bromodeoxyuridine-labeled nascent DNA indicated that oriA1 is not utilized in AldB-expressing cells, while it is fired in non-expressing cells. In the latter non-expressing cells, the replication fork seemed to slow at 20-22 kb downstream of oriA1.