Sumoylation is one of the post-translational modifications of proteins, responsible for the regulation of many cellular processes, such as DNA replication and repair, transcription, signal transduction and nuclear transport. During sumoylation, SUMO proteins are covalently attached to the ε-amino group of lysine in target proteins via an enzymatic cascade that requires the sequential action of E1, E2 and E3 enzymes. An important aspect of sumoylation is its reversibility, which involves SUMO-specific proteases called SENPs. SENPs (sentrin/SUMO-specific proteases) catalyze the deconjugation of SUMO proteins using their isopeptidase activity. These enzymes participate through hydrolase activity in the reaction of SUMO protein maturation, which involves the removal of a short fragment on the C-terminus of SUMO inactive form and exposure two glycine residues. SENPs are important for maintaining the balance between sumoylated and desumoylated proteins required for normal cellular physiology. Six SENP isoforms (SENP1, SENP2, SENP3, SENP5, SENP6 and SENP7) have been identified in mammals. These SENPs can be divided into three subfamilies based on their sequence homology, substrate specificity and subcellular localization. Results of studies indicate the role of SUMO proteases in the development of human diseases including cancer, suggesting that these proteins may be attractive targets for new drugs.
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