The proximity interactome of PML isoforms I and II under fatty acid stress.

Promyelocytic leukemia (PML) protein forms the scaffold for PML nuclear bodies (PML NB) that reorganize into Lipid-Associated PML Structures (LAPS) under fatty acid stress. We determined how the fatty acid oleate alters the interactome of PMLI or PMLII by expressing fusions with the ascorbate peroxidase APEX2 in U2OS cells. The resultant interactome included ESCRT and COPII transport protein nodes. Proximity ligation assay (PLA) revealed that COPII proteins SEC23B, SEC24A and USO1 preferentially associated with PML NBs. Nuclear localization of USO1, but not SEC23B and SEC24A, was reduced in PML knockout cells and restored by PMLII expression. Thus, proximity-labelling methods identified COPII transport protein interactions with PML NBs that are disrupted by fatty acid stress.