Together with PML, this tumor suppressor is a major constituent of the PML bodies, a subnuclear organelle involved in a large number of physiological processes including cell growth, differentiation and apoptosis. Functions as a transcriptional coactivator of ETS1 and ETS2. Under certain conditions, it may also act as a corepressor of ETS1 preventing its binding to DNA. Through the regulation of ETS1 it may play a role in angiogenesis, controlling endothelial cell motility and invasion. Through interaction with the MRN complex it may be involved in the regulation of telomeres lengthening. May also regulate TP53-mediated transcription and through CASP8AP2, regulate FAS-mediated apoptosis. May also play a role in infection by viruses through mechanisms that may involve chromatin and/or transcriptional regulation (By similarity). Homodimer. Interacts with members of the HP1 family of nonhistone chromosomal protein, such as CBX5 and CBX3 via the PxVxL motif. Interacts with ETS1; the interaction is direct and modulates ETS1 transcriptional activity. Interacts with the MRN complex which is composed of two heterodimers RAD50/MRE11 associated with a single NBN; recruits the complex to PML-related bodies. Interacts with HIPK2; positively regulates TP53-dependent transcription. Interacts with CASP8AP2; may negatively regulate CASP8AP2 export from the nucleus to the cytoplasm (By similarity). Accumulates in the cytoplasm upon FAS activation. Phosphorylated. Sumoylated. Sumoylated with SUMO1. Sumoylation depends on a functional nuclear localization signal but is not necessary for nuclear import or nuclear body targeting. Sumoylation may stabilize the interaction with CBX5 (By similarity).