USP35 activated by miR let-7a inhibits cell proliferation and NF-κB activation through stabilization of ABIN-2.

Chunyan Liu,Pengju Zhang,Yani Lin,Anli Jiang,Shihu Zhao,Weiwen Chen,Lina Wang,Chunli Yin

doi:10.18632/oncotarget.4451

Abstract

Ubiquitin specific protease 35 (USP35) is a member of deubiquitylases (DUBs). It remains largely unknown about the biological role and the regulation mechanism of USP35. Here, we first identified miR let-7a as a positive regulator of USP35 expression and showed that USP35 expression positively correlates with miR let-7a expression in different cancer cell lines and tissues. Then, we showed that USP35 expression was decreased dramatically in the tumor tissues compared with the adjacent non-cancerous tissues. USP35 overexpression inhibited cell proliferation in vitro and inhibited xenograft tumor growth in vivo. Furthermore, we revealed that USP35 acts as a functional DUB and stabilizes TNFAIP3 interacting protein 2 (ABIN-2) by promoting its deubiquitination. Functionally, both ABIN-2 and USP35 could inhibit TNFα-induced NF-κB activation and overexpression of ABIN-2 alleviated USP35-loss induced activation of NF-κB. Collectively, our data indicated that miR let-7a-regulated USP35 can inhibit NF-κB activation by deubiquitination and stabilization of ABIN-2 protein and eventually inhibit cell proliferation. Overall, our study provides a novel rationale of targeting miR let-7a-USP35-ABIN-2 pathway for the therapy of cancer patients.

Highlights

MicroRNA (MiR) let-7a has been widely studied and functions as a tumor suppressor [1]
To confirm the results obtained from analyzing the mRNA profiling, we transfected let-7a mimics or inhibitor into LNCaP cells and used Quantitative real time polymerase chain reaction (qRT-PCR) and Western blot to detect the expression of Ubiquitin specific protease 35 (USP35)
Consistent with the results of microarray analysis, the results showed that let-7a mimics increased, whereas let-7a inhibitor decreased both mRNA and protein level of USP35 (Figure 1A–1C)

Summary

Introduction

MicroRNA (MiR) let-7a has been widely studied and functions as a tumor suppressor [1]. Previous work has shown miR let-7a inhibits cell proliferation by downregulating oncogenes RAS/c-MYC [5] and HMGA-2 [6] at the translational level in lung cancer cells. MiR let-7a targets E2F2 and CCND2 to inhibit cell proliferation [4]. We previously demonstrated that miR let-7a directly targets the 3′ UTR of the IGF1R mRNA and inhibits its expression in prostate cancer cells [7]. Accumulating evidences indicate that miR let-7a exerts its anti-tumor activity by regulating oncogenes or tumor suppressor genes [8], the precise mechanisms of miR let-7a in the pathogenesis of human cancers still remain unclear and the full set of its regulatory substrates need to be further elucidated

Methods

Results

Conclusion