| TRAF 7 has an E 3 ubiquitin ligase activity for self ubiquitination , but TRAF 7 also stimulated the sumoylation of c Myb at Lys 523 and Lys 499 , which are the same sites as those used for PIASy induced sumoylation . ^^^ Overexpressed TRAF 7 was localized in the cytoplasm of CV 1 cells , and sequestered c Myb and SUMO 1 in the cytosol , whereas PIASy was localized in the nucleus . ^^^ |