The SUMO3 precursor has 11 extra residues at the C-terminus which can be removed endoproteolytically by SENP1, SENP2, or SENP5 (Zheng and Au, 2005, Gong and Yeh 2006, Mikolajczyk et al. 2007). The order of processing activity is: SENP1 greater than SENP2 greater than SENP5 (Mikolajczyk et al. 2007). Overall, processing of SUMO3 is the lowest of any SUMO (Mikolajczyk et al. 2007). SENP1 and SENP2 shuttle between the nucleus and cytosol and are predominantly nuclear (Bailey and O'Hare 2004, Kim et al. 2005, Zhang et al. 2002, Hang and Dasso 2002, Itahana et al. 2006). SENP5 is located in the nucleolus (Di Bacco et al. 2006, Gong and Yeh 2006).