Atypical plant homeodomain of UBR7 functions as an H2BK120Ub ligase and breast tumor suppressor

Santanu Adhikary,Chandrima Das,Coya Tapia,Aysegul A Sahin,Roland Bassett,Christopher Terranova,Fei Yang,Anirban Dasgupta,Mayinuer Maitituoheti,Kunal Rai,Dushyant Kumar Srivastava,Ayush T Raman,Deepavali Chakravarti,Isha Sengupta,Siddhartha Roy,Junsheng Ma,Emily Tarco

doi:10.1038/s41467-019-08986-5

Abstract

The roles of Plant Homeodomain (PHD) fingers in catalysis of histone modifications are unknown. We demonstrated that the PHD finger of Ubiquitin Protein Ligase E3 Component N-Recognin7 (UBR7) harbors E3 ubiquitin ligase activity toward monoubiquitination of histone H2B at lysine120 (H2BK120Ub). Purified PHD finger or full-length UBR7 monoubiquitinated H2BK120 in vitro, and loss of UBR7 drastically reduced H2BK120Ub genome-wide binding sites in MCF10A cells. Low UBR7 expression was correlated with occurrence of triple-negative breast cancer and metastatic tumors. Consistently, UBR7 knockdown enhanced the invasiveness, induced epithelial-to-mesenchymal transition and promoted metastasis. Conversely, ectopic expression of UBR7 restored these cellular phenotypes and reduced tumor growth. Mechanistically, UBR7 loss reduced H2BK120Ub levels on cell adhesion genes, including CDH4, and upregulated the Wnt/β-Catenin signaling pathway. CDH4 overexpression could partially revert UBR7-dependent cellular phenotypes. Collectively, our results established UBR7 as a histone H2B monoubiquitin ligase that suppresses tumorigenesis and metastasis of triple-negative breast cancer.

Highlights

The roles of Plant Homeodomain (PHD) fingers in catalysis of histone modifications are unknown
Ubiquitin Protein Ligase E3 Component N-Recognin7 (UBR7), a protein with an unknown function, contains a ubiquitin protein ligase E3 component N-recognin (UBR)-box domain, which is essential for the recognition of Ndegrons[20,21,22], and a PHD finger (Fig. 1a), which is highly conserved across species (Supplementary Fig. 1a)
Full-length UBR7 protein interacted with all recombinant histones in vitro, the PHD finger preferentially interacted with recombinant histone H2B (Fig. 1b) and could immunoprecipitate them from MCF10A cells (Supplementary Fig. 1g)

Summary

Introduction

The roles of Plant Homeodomain (PHD) fingers in catalysis of histone modifications are unknown. We demonstrated that the PHD finger of Ubiquitin Protein Ligase E3 Component N-Recognin[7] (UBR7) harbors E3 ubiquitin ligase activity toward monoubiquitination of histone H2B at lysine[120] (H2BK120Ub). Our results established UBR7 as a histone H2B monoubiquitin ligase that suppresses tumorigenesis and metastasis of triple-negative breast cancer. The members of the UBR family of proteins are generally heterogeneous in size and sequence, they harbor specific signatures unique to ubiquitin ligases or a substrate-recognition subunit of the E3 complex like the RING/HECT (really interesting new gene/homologous to the E6AP carboxyl terminus) domain or F-box[21,22]. We demonstrated that the UBR7-PHD finger is an H2BK120 monoubiquitin ligase and a tumor suppressor in triple-negative breast cancer cases

Methods

Results

Conclusion