Abstract 4966: Identification of deubiquitinating enzyme USP19 as a regulator of EWS/FLI1 protein turnover in Ewing sarcoma

Ewing sarcoma belongs to the family of pediatric tumors which arise most commonly in bone. The majority of Ewing sarcoma is characterized by a balanced translocation between chromosomes 11 and 22 which encodes for the uniquely expressed fusion protein EWS/FLI1. Tumor cells are crucially dependent on expression of the fusion protein. Protein degradation is an important and highly regulated process in all cells and novel insights are beginning to be applied for cancer therapy. We aim to investigate the mechanism of turnover with the goal to diminish EWS/FLI1 protein and thereby identify novel targets for Ewing sarcoma treatment.Here, we show first that EWS/FLI1 protein stabilizes upon proteasome inhibition. Co-immunoprecipitation of EWS/FLI1 with ubiquitin shows a characteristic ubiquitination smear indicating that EWS/FLI1 is ubiquitinated and a substrate of the ubiquitin-proteasome system. We characterized the turnover itself as rather slow. Interestingly, the half-life time of the fusion protein is increased by four-fold compared to the full length protein FLI1. This increased stability possibly contributes to the oncogenic and resistant features of the fusion protein.To identify a deubiquitinating enzyme capable of regulating EWS/FLI1 turnover, we selected 20 deubiquitinating enzymes based on their expression in Ewing cell lines and tumors in-silico. Then, we established a screening approach directly measuring EWS/FLI1 protein levels as a read-out by an ELISA-like assay, al...
Source: Cancer Research - Category: Cancer & Oncology Authors: Tags: Molecular and Cellular Biology Source Type: research