Representative Western blots illustrating the expression of SMC6 and of monoubiquitylated FANCD2 in protein extracts from HeLa cells transfected with the indicated siRNAs and treated 48 hours after transfection with HU (5mM, 18 hours) or Mitomycin C (200 ng/ml, 18 hours). Vinculin is used as loading control. 