PML nuclear bodies (NBs) are nuclear structures that have been implicated in processes such as transcriptional regulation, genome stability, response to viral infection, apoptosis, and tumor suppression. Unlike other, more specialized subnuclear structures such as Cajal and Polycomb group bodies, PML-NBs are functionally promiscuous and have been implicated in the regulation of diverse cellular functions. PML-NBs are dynamic structures that favour the sequestration and release of proteins, mediate their post-translational modifications and promote specific nuclear events in response to various cellular stresses. Post-translational modification (especially SUMOylation) of both the PML scaffold and clients can regulate client recruitment to PML NBs. Phosphorylation of the Daxx SUMO interacting motif increases its affinity for SUMO-1 and, presumably, SUMOylated PML. Several results illustrate how SUMOylation of PML and SUMOylation or phosphorylation of clients can regulate the composition of PML NBs through modulating scaffold–client interactions. PML is the only protein that has been found to be essential for the formation of the NBs; and these structures do not form in PML null cells, although PML add back fully rescues their formation (PMID:17081985, PMID:17928811, PMID:30099028).