USP9X-mediated deubiquitination of B-cell CLL/lymphoma 9 potentiates Wnt signaling and promotes breast carcinogenesis

• Published in: The Journal of biological chemistry 2019-06, Vol.294 (25), p.9844-9857
• Main Authors: Shang, Zesen, Zhao, Jiao, Zhang, Qi, Cao, Cheng, Tian, Shanshan, Zhang, Kai, Liu, Ling, Shi, Lei, Yu, Na, Yang, Shangda
• Format: Article
• Language: English
• Subjects: B-cell CLL/lymphoma 9 (BCL9); beta Catenin - genetics; beta Catenin - metabolism; breast cancer; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; carcinogenesis; Cell Biology; Cell Movement; Cell Proliferation; cell signaling; deubiquitylation (deubiquitination); Female; Gene Expression Regulation, Neoplastic; Humans; Lys-63–linked polyubiquitins; Proteolysis; Transcription Factors - genetics; Transcription Factors - metabolism; Tumor Cells, Cultured; Ubiquitin - metabolism; Ubiquitin Thiolesterase - genetics; Ubiquitin Thiolesterase - metabolism; ubiquitin-specific peptidase 9, X-linked (USP9X); Wnt pathway; Wnt1 Protein - genetics; Wnt1 Protein - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.RA119.007655

Hyperactivation of the canonical Wnt-signaling pathway is a prominent feature of a number of human malignancies. Transcriptional activation of this signaling cascade depends on the formation of the β-catenin–B-cell CLL/lymphoma 9 (BCL9)–pygopus (PYGO) family plant homeodomain finger 1 complex, yet how the assembly of this complex is regulated remains to be investigated. Here, using MCF-7, HeLa, HEK293T, MDA–MB-231, and Sf9 cells, along with immunoblotting and immunofluorescence, nano-HPLC–MS/MS, deubiquitination, immunoprecipitation, and chromatin immunoprecipitation (ChIP) assays, we report that BCL9 physically associates with a protein deubiquitinase, ubiquitin-specific peptidase 9, X-linked (USP9X), and that USP9X removes Lys-63–linked polyubiquitin on Lys-212 of BCL9. Importantly, the USP9X-mediated BCL9 deubiquitination facilitated the formation of the β-catenin–BCL9–PYGO complex, thereby potentiating the transcriptional activation of Wnt/β-catenin target genes. We also show that USP9X-mediated BCL9 deubiquitination promotes the proliferation and invasion of breast cancer cells. Together, these results uncover USP9X as a deubiquitinase of BCL9, implicating USP9X in Wnt/β-catenin signaling and breast carcinogenesis.