The localization of the key SAC component BubR1 (budding uninhibited by benzimidazoles related 1) (35) to kinetochores [labeled with serum from patients with CREST (calcinosis, Raynaud phenomenon, esophageal dismotility, scierodactyly, telangiectasia) scleroderma] was significantly reduced in XPD/R683W cells (Fig. 6D, plot 2; Fig. 6E, images E.3 and E.4; fig. The gene discussed is BUB1B; the disease is xeroderma pigmentosum group D.