Suppression of USP7 negatively regulates the stability of ETS proto-oncogene 2 protein

Abstract

Ubiquitin-specific protease 7 (USP7) is one of the deubiquitinating enzymes (DUBs) that remove mono or polyubiquitin chains from target proteins. Depending on cancer types, USP7 has two opposing roles: oncogene or tumor suppressor. Moreover, it also known that USP7 functions in the cell cycle, apoptosis, DNA repair, chromatin remodeling, and epigenetic regulation through deubiquitination of several substrates including p53, mouse double minute 2 homolog (MDM2), Myc, and phosphatase and tensin homolog (PTEN). The [P/A/E]-X-X-S and K-X-X-X-K motifs of target proteins are necessary elements for the binding of USP7. In a previous study, we identified a novel substrate of USP7 through bioinformatics analysis using the binding motifs for USP7, and suggested that it can be an effective tool for finding new substrates for USP7. In the current study, gene ontology (GO) analysis revealed that putative target proteins having the [P/A/E]-X-X-S and K-X-X-K motifs are involved in transcriptional regulation. Moreover, through protein-protein interaction (PPI) analysis, we discovered that USP7 binds to the AVMS motif of ETS proto-oncogene 2 (ETS2) and deubiquitinates M1-, K11-, K27-, and K29-linked polyubiquitination of ETS2. Furthermore, we determined that suppression of USP7 decreases the protein stability of ETS2 and inhibits the transcriptional activity of ETS2 by disrupting the binding between the GGAA/T core motif and ETS2. Therefore, we propose that USP7 can be a novel target in cancers related to the dysregulation of ETS2.