Arsenic induces two different interaction modes of SUMO with promyelocytic leukemia (PML) proteins.

Promyelocytic leukemia-nuclear bodies (PML-NBs) are dot-like protein assemblies and implicated in the pathogenesis of leukemia and viral infection. PML is the scaffold protein of PML-NB and its client proteins such as SUMO, DAXX, and Sp100 reside in PML-NBs. It is known that a short exposure to trivalent arsenic (As3+) induces the solubility change and the subsequent SUMOylation of PML, and the SUMO interacting motif (SIM) is not necessary for these biochemical changes. However, it has not been well studied how As3+ initiates or enhances the association of SUMO with PML and the other PML-NB client proteins. Here, we report that As3+ enhanced non-covalent association of PML with SUMO via the SUMO-SIM interaction which is dispensable for the solubility change and SUMOylation of PML. We also report that the As3+-induced solubility change of PML was not affected by ML792, a SUMO E1 enzyme inhibitor, even though the nuclear localization of SUMO2/3 and protein SUMOylation were halted by ML792. As3+ did not change the solubility of DAXX and SUMOylation enzymes such as SAE1, UBA2, and UBC9. In contrast, As3+ induced SUMOylation of Sp100 with a concomitant loss of its solubility like PML in human leukemia cell lines. Our current results indicate that both covalent and non-covalent associations of SUMO with PML are increased in As3+-exposed cells, and Sp100 may play a role in the maintenance of PML-NBs.