Schematic summary of the nuclear import of TopBP1 for DNA replication (Replication) and DNA damage response (Checkpoint) in three different scenarios: (1) Scenario #1, recombinant WT or ΔCTM TopBP1 was added to egg extracts after nuclear membrane is formed; (2) Scenario #2, recombinant WT or ΔCTM TopBP1 was added to egg extracts before nuclear membrane is formed; and (3) Scenario #3, recombinant WT or ΔCTM TopBP1 was added to TopBP1-depleted extracts supplemented with ATR activation structure AT70, which did not form any nuclei. “YES” represents sufficiency, and “NO” represents deficiency.