NFKB1 and malignant colon neoplasm: Although both Uev1A and Mms2 are cofactors of Ubc13 that together mediate K63-linked polyubiquitination, their biological functions are apparently distinct and only the Uev1A-Ubc13 complex is involved in NF-κB signaling and promotes metastasis in breast and colon cancers [7, 20, 28, 29].