Association of TopBP1 and Cdc45 with DNA.

The association of each of the indicated purified proteins with beads alone (No DNA) or to single-stranded (ss), double-stranded (ds), and branched, replication fork-like (fork) DNA bound to magnetic beads was analyzed by SDS-PAGE and immunoblotting. Each of the following proteins was analyzed for binding to each DNA structure: (A) TopBP1 and (B) Cdc45. Reactions were carried out as described in the Methods section.