FIGURE 5.

A, schematic diagram of reciprocal modification and regulation between Rsp5p and Siz1p. Covalent attachment (gray arrows) of ubiquitin (Ub) or SUMO alters activity of the modified ligase and has a concomitant effect on downstream processes such as Smf1p endocytosis and SUMO chain formation. B, human PIAS family of SUMO ligases with conserved PY motifs. ClustalW alignment (using MegAlign software, DNASTAR®Lasergene) shows the regions of protein sequences of human PIAS ligases (NCBI) with putative PY motifs highlighted in bold. Conserved residues within the regions are shown with asterisks, similar residues are highlighted with square dots.