FBL and systemic sclerosis: Increased sumoylation of topo I (higher intensity of the bands and presence of poly-sumoylation of topo I) evaluated by IP Western blots was clearly observed in 7 of 11 SSc fibroblast strains (2 anti-topo I positive patients, 4 anti-RNA polymerase III positive patients and 1 anti-fibrillarin positive patient (Figure 3).