TRAP1 is a Novel Interaction Partner of PML, Localized with PML in Nuclear Bodies and Relocating with PML to the Cytoplasm Following Stress

Abstract

Aims: The aim of the study was to identify a novel interaction partner of PML and to study the localization of the novel protein complex in cells. Study Design: Isolation of PML and interacting protein complexes by co-immunoprecipitation using a PML antibody and subsequent mass spectrometry analyses. Place and Duration of Study: Department of Medical and Molecular Genetics, Guy’s Hospital, London between 2002 and 2005 and Cancer Stem Cell Innovation Centre and Department of Tumor Biology, Norwegian Radium Hospital, Oslo between 2011-2014. Methodology: Interacting proteins of PML were isolated from K562 cell lysates by large scale co-immunoprecipitation and mass spectrometry. The complex formation was confirmed by standard co-immunoprecipitations and confocal microscopy. The cellular localization of the protein complex was further studied by confocal microscopy in different cell types and following exposure to stress. Results: We have identified tumor necrosis factor receptor protein 1 (TRAP1) as an interacting partner of PML. A fraction of TRAP1 is localized to PML nuclear bodies (NBs) in human cancerous cells and normal mouse embryonic fibroblasts, indicating conservation across species. PML and TRAP1 are both implicated in regulation of cell death and survival, with PML acting as an inducer of apoptosis and TRAP1 as protector from cell death. Exposure to stress, results in relocation of TRAP1 - PML from NBs to cytoplasmic punctate structures, indicating a role for this complex in stress-response. Conclusion: TRAP1 and PML interact in normal and cancerous cells. The complex may play a role in stress response.