Fig. 7
From: Site-specific characterization of endogenous SUMOylation across species and organs
Insight into the SUMO equilibrium. a Overview of the SUMOylation cycle, highlighting different pools of SUMO2/3 that can be quantified using our purification strategy. Notably, conjugated SUMO2/3 and free SUMO2/3 can be quantified, along with immature free SUMO. Conjugated SUMO2/3 was further split into SUMO covalently conjugated to the E1, E2, or E3 enzymes, to other SUMO (chain), or to any other target protein. Note that the usual transfer of SUMO from E1 to E2 to target requires the cysteine and does not end up on lysines within the same enzymes, but transfer to lysines in SUMO enzymes can occur when the enzymes are active in close proximity to each other. b Quantification of the SUMO2/3 equilibrium in human cell lines in response to various treatments, visualizing the fraction of total SUMO existing as conjugated to certain target proteins, or as free SUMO. Error bars represent SD, n = 3 cell culture replicates. c As (b), but quantifying the SUMO2/3 equilibrium in different mouse organs. Error bars represent SEM, n = 5 animals. Asterisks indicate significant differences (blue, higher; red, lower) between the indicated organ and the six median organs within the same category, by two-tailed Student’s t-test. **P < 0.001, *P < 0.05. d Quantification of endogenous SUMO2/3 chain architecture in HEK cells in response to various treatments, corresponding to endogenous SUMO-2 modified by SUMO-2/3. Error bars represent SD, n = 3 cell culture replicates. e As (d), but quantifying the SUMO-2 chain architecture in different mouse organs. Error bars represent SEM, n = 5 animals
