SUMO2 and neoplasm: Thus, we wondered whether Sp1 can be conjugated with SUMO2/3 and be a substrate of SENP3, as we have previously shown that the protein level of SENP3, a SUMO2/3 specific protease, is increased in tumor tissues and under various stress conditions (Han et al., 2010; Huang et al., 2009; Yan et al., 2010).