The Deubiquitinase USP28 Stabilizes LSD1 and Confers Stem-Cell-like Traits to Breast Cancer Cells

Yadi Wu,Yifan Wang,Xiuwei H Yang,Tiebang Kang,Yongxiang Zhao,Chi Wang,B Mark Evers,Binhua P Zhou

doi:10.1016/j.celrep.2013.08.030

Yadi Wu, Yifan Wang + Show 6 more

Open Access

https://doi.org/10.1016/j.celrep.2013.08.030

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Abstract

LSD1 is a critical chromatin modulator that controls cellular pluripotency and differentiation through the demethylation of H3K4me1/2. Overexpression of LSD1 has been observed in many types of tumors and is correlated with its oncogenic effects in tumorigenesis. However, the mechanism leading to LSD1 upregulation in tumors remains unclear. Using an unbiased siRNA screening against all the human deubiquitinases, we identified USP28 as a bona fide deubiquitinase of LSD1. USP28 interacted with and stabilized LSD1 via deubiquitination. USP28 overexpression correlated with LSD1 upregulation in multiple cancer cell lines and breast tumor samples. Knockdown of USP28 resulted in LSD1 destabilization, leading to the suppression of cancer stem cell (CSC)-like characteristics invitro and inhibition of tumorigenicity invivo, which can be rescued by ectopic LSD1 expression. Our study reveals a critical mechanism underlying the epigenetic regulation by USP28 and provides another treatment approach against breast cancer.

Highlights

This initial screen identified 24 genes that may directly or indirectly control Lysine-specific demethylase 1 (LSD1) stability. When these DUBs were co-expressed with LSD1 in HEK293 cells, we noticed that USP28 significantly increased LSD1 level, similar to that treated with MG132 (Figure S1A)
This observation was further confirmed with immunofluorescent analysis showing that the loss of LSD1 staining co-localized with USP28-knockdown in nuclei (Figure 1F)
Because LSD1 is a major demethylase for H3K4me2, we examined the global levels of H3K4me2 in HCT116 cells with USP28-knockdown

Summary

SUMMARY

LSD1 is a critical chromatin modulator controlling cellular pluripotency and differentiation through the demethylation of H3K4me1/2. Our study reveals a critical mechanism underlying the epigenetic regulation by USP28 and provides a new treatment approach against breast cancer. Posttranslational modifications, such as phosphorylation, acetylation and methylation of histone tails are crucial epigenetic marks that regulate diverse cellular processes. Methylation, in particular, has a global effect on cell cycle control, tumor progression and embryonic stem cell (ESC) self-renewal and differentiation (Klose and Zhang, 2007; Shi, 2007). Despite the fact that LSD1 is an important determinant of stem cell pluripotency and differentiation and its critical role in tumorigenesis, the mechanism leading to the aberrant upregulation of LSD1 in tumor remains unclear.

RESULTS

DISCUSSION

EXPERIMENTAL PROCEDURES