Fig. 6. The pattern of SUMO-conjugated substrates changes during HaCaT cell differentiation. Total cell extracts were prepared at the indicated times post Ca²⁺ induction and analyzed by immunoblotting using antibodies to SUMO1 (upper panel), -tubulin (middle panel) or keratin 1 (lower panel). Protein concentrations in the samples were equalized based on the -tubulin levels. The positions of molecular size markers are shown on the right. Arrows and arrowheads indicate bands whose quantity increased or decreased, respectively, during the time period examined.