ATF is important to late S phase-dependent regulation of DNA topoisomerase IIalpha gene expression in HeLa cells.

DNA topoisomerase IIalpha (Topo IIalpha) is regulated in late S phase-dependent manner. To identify late S phase-dependent cis-acting elements of Topo IIalpha gene, we have investigated the synchronized HeLa cells with chloramphenicol acetyltransferase and DNase I footprinting assays. The level of Topo IIalpha mRNA increased after release from aphidicolin block and reached a maximum in 8h (late S phase) in HeLa cells, and Topo II unknotting activity was also in parallel with the level of Topo IIalpha mRNA.