Superposition of Sir4 H‑BRCT (orange) onto the Dbf4-Rad53-CDC7 complex (cyan, grey, blue) (PDB 5T2S) in two orientations rotated by ~180° around a vertical axis. Helices are displayed as barrels and protein-protein interfaces between Dbf4 and FHA1 of Rad53 are highlighted with dashed circles in black (interface I) and blue (interface II). 