TRIM29 protein partners in cultured immortalized normal basal epithelial cells of the prostate

BACKGROUND: The E3 ubiquitin ligase TRIM29 is involved in basal epithelial development, cellular response to viral infection, and DNA damage. Furthermore, this protein can have both oncogenic and tumor suppressor properties. However, the molecular mechanisms of TRIM29 involvement in such a wide range of biological processes remain unclear. AIM: To identify protein partners of TRIM29 and its truncated forms and to determine the key molecular processes in which it is involved. MATERIALS AND METHODS: Cell cultures of normal prostate basal epithelium with overexpression of a full length TRIM29-FLAG chimeric protein or its truncated forms without the B-box or Coiled-Coil domain were obtained. Subsequently, protein partners of TRIM29 and truncated forms of TRIM29 were identified by protein immunoprecipitation followed by proteomic analysis (high-performance liquid chromatography with tandem mass spectrometry). Results were confirmed by Western blot and immunocytochemistry. RESULTS: TRIM29 binds to 288 proteins in the normal basal epithelium of the prostate. Deletion of the B-box has little effect on TRIM29 protein-protein interactions, whereas deletion of the Coiled-Coil domain deprives TRIM29 of most of its protein partners and impairs its dimerization. TRIM29 was found to localize to both the nucleus and cytoplasm, while deletion of functional domains does not prevent localization to different compartments, but does affect binding to proteins specific to these compartments. TRIM29 binds to cytoskeleton proteins, cellular stress response proteins, and RNA-binding proteins. In addition, TRIM29 is shown to increase cell resistance to genotoxic agents and to affect RNA splicing. CONCLUSION: Proteomic analysis showed that in normal prostate basal epithelium, E3 ubiquitin ligase TRIM29 binds to a relatively large number of proteins that perform different functions in different cell compartments. Our results are consistent with results obtained by other research teams who showed that TRIM29 is actively involved in cytoskeletal remodeling, cellular response to viral infection, and DNA damage. In addition, it was shown for the first time that TRIM29 interacts with stress granule proteins and RNA binding proteins and is able to regulate RNA splicing, and the Coiled-Coil domain of TRIM29 may play a key role in this process.