Figure 3. Ubiquitin conjugation pathway and enzymes involved in PCNA ubiquitination.
Cartoon depiction of the ubiquitin conjugation pathway. Ubiquitination occurs through at least three concerted reactions. Enzymes responsible for mono- and polyubiquitination of PCNA are as indicated. Human homologs of yeast Rad5 are in parenthesis. E1 = ubiquitin activating enzyme (yellow). E2 = ubiquitin conjugating enzyme (green). E3 = ubiquitin ligase (red). DUB = deubiquitinating enzyme (orange). Ub = ubiquitin. Substrate is shown in purple.