Primary lymphocytes from patients with Fanconi anemia fail to monoubiquitinate FANCD2.

(A) Lymphocytes isolated from healthy control volunteers were stimulated with PHA for up to 72 hours prior to immunoblotting with antibodies against the indicated FANC proteins. Expression levels of all 4 Fanconi proteins rose following 72 hours of PHA stimulation. (B) Protein extracts of lymphocytes isolated from healthy control volunteers or from patients with Fanconi anemia were immunoblotted for FANCD2 following PHA stimulation. Although the lymphocytes from healthy control volunteers showed both the unmodified (FANCD2-S) and the monoubiquitinated (FANCD2-L) FANCD2 forms, the lymphocytes from the patients with Fanconi anemia showed only the lower unmodified FANCD2-S form. (C) Protein extracts from lymphocytes from obligate FA heterozygous carriers were immunoblotted for FANCD2 following PHA stimulation.