TRIM3 Negatively Regulates Autophagy Through Promoting Degradation of Beclin1 in Ewing Sarcoma Cells

BACKGROUND AND AIM: Ewing sarcoma (ES) is an aggressive neoplasm predominantly occurring in adolescents and has a poor prognosis when metastasized. In the current study, we were aiming to investigate the function of TRIM3 in autophagy in ES cells. METHODS: The expression of TRIM3 in Ewing sarcoma tissues and normal tissues was examined by quantitative PCR and western blot. The effect of TRIM3 on autophagy was detected by western blot and immunofluorescence assay. Target of TRIM3 was examined by western blot, immunoprecipitation and ubiquitination assay. RESULTS: We found the expression of TRIM3 was significantly up-regulated in Ewing sarcoma tissues compared with normal tissues, and this phenomenon was regulated by EWS-FLI1 expression. Furthermore, we observed that overexpression of TRIM3 markedly and consistently inhibited autophagy in ES cells, and autophagy was enhanced in TRIM3-silenced ES cells. Finally, we found in ES cells, TRIM3 could directly interact with Beclin1, and improved its K48-linked polyubiquitinaion, leading to the degradation of Beclin1 and then regulated autophagy. CONCLUSION: In the present research, for the first time we revealed that TRIM3 negatively regulates autophagy through promoting degradation of Beclin1 in Ewing sarcoma cells, and these findings may provide ideas for ES research.