Fanconi anemia (subtype A) cells are defective in the monoubiquitination of the FANCD2 protein during S phase.

SV40-transformed fibroblasts from an FA-A patient (GM6914) and GM6914 cells corrected with FANCA cDNA were compared. Cells were synchronized by either the double-thymidine–block method (A) or the nocodazole block method (B). FANCD2 was examined by anti-FANCD2 immunoblotting.