FIGURE 7.
Increased SUMO expression and SUMO-2/3 modification of insoluble mouse liver proteins during chronic liver injury. A, total cell lysates were prepared from separate livers of three untreated (1–3) and four DDC-treated (4–7) FVB/N mice. The detergent-soluble fractions were analyzed by SDS-PAGE followed by Coomassie staining (loading control) or immunoblot for the presence of monomeric SUMO-1 and SUMO-2/3 isoforms (∼15 kDa). B, the corresponding HSEs of the liver lysates in A were analyzed by immunoblotting using antibodies to SUMO-1 and SUMO-2/3. The asterisks denote SUMO complexes that likely include lamin A and/or RanGAP1. C, the liver HSEs from control and DDC-treated mice were analyzed for the expression of K8, K18, and K19 (as loading controls). Note that there is keratin induction during liver injury in addition to K8 phosphorylation at Ser79. The monomeric proteins are distinguished from the HMW keratin-containing complexes, which are primarily observed after DDC treatment, similar to the SUMO-2/3-containing HMW complexes (B).