Intracellular communication via ubiquitin (Ub) signaling impacts all aspects of cell biology and regulates pathways critical to human development and viability; therefore aberrations or defects in Ub signaling can contribute to the pathogenesis of human diseases. Ubiquitination consists of the addition of Ub to a substrate protein via coordinated action of E1-activating, E2-conjugating and E3-l...

The ubiquitin-like protein SMT3 from Saccharomyces cerevisiae and SUMO-1, its mammalian homolog, can be covalently attached to other proteins posttranslationally. Conjugation of ubiquitin requires the activities of ubiquitin-activating (E1) and -conjugating (E2) enzymes and proceeds via thioester-linked enzyme-ubiquitin intermediates. Herein we show that UBC9, one of the 13 different E2 enzymes...

Ubiquitin-conjugating enzyme variant (UEV) proteins resemble ubiquitin-conjugating enzymes (E2s) but lack the defining E2 active-site residue. The MMS2-encoded UEV protein has been genetically implicated in error-free postreplicative DNA repair in Saccharomyces cerevisiae. We show that Mms2p forms a specific heteromeric complex with the UBC13-encoded E2 and is required for the Ubc13p-dependent ...