Structure and Function of the N-terminal Domains of SUMO Ligase Siz/PIAS Family

摘要

The ubiquitin (Ub)-related protein SUMO functions by becoming covalently attached to other proteins as a post-translational modification, and SUMO conjugation, so-called sumoylation, is essential for viability of eukaryotic cells. Like Ub, SUMO is attached to certain lysine residues in substrates through an amide bond between the C-terminus of SUMO and the ε-amino group of the lysine residue. Sumoylation is involved in many cellular processes, such as transcription, nuclear transport, signal transduction, maintenance of chromatin and so on. The effect of sumoylation could be diverse. It can affect the localization, or regulate the activity or the binding properties of the target proteins. In contrast to ubiquination, however, sumoylation does not promote protein degradation, and in some cases, it can even antagonize ubiquitination and lead to protein stabilization. Sumoylation, like ubiquitination, is also carried out by the sequential action of three enzymes: an activation enzyme (E1), a conjugating enzyme (E2) and a ligase (E3). In all of the organisms examined so far, a single E1 and E2 but multiple E3s have been detected. Thus, E3s are likely the determinants of substrate specificity.