Ubiquitin-Conjugating Enzyme 2S Enhances Viral Replication by Inhibiting Type I IFN Production through Recruiting USP15 to Deubiquitinate TBK1
Authors: Huang, Li; Liu, Hongyang; Zhang, Kunli; Meng, Qingwen; Hu, Liang; Zhang, Yuanfeng; Xiang, Zhida; Li, Jiangnan; Yang, Yuying; Chen, Yali; Cui, Shangjin; Tang, Hong; Pei, Huadong; Bu, Zhigao; Weng, Changjiang
Type I interferon (IFN) plays an essential role in the host innate immune responses. Several ubiquitin-conjugating enzyme (E2) family members were reported to regulate type I IFN production and host antiviral immune responses. However, the molecular mechanisms are still not fully understood. Here, we report that UBE2S acts as a negative regulator in the type I IFN signaling pathway. Ectopic expression of UBE2S inhibits host antiviral immune responses and enhances viral replications, whereas deficiency of UBE2S enhances host antiviral immune responses and suppresses viral replications both in vitro and in vivo. Inhibition of type I IFN production by UBE2S is independent on its E2 and E3 enzymic activity. Mechanistically, UBE2S interacts with TBK1 and recruits ubiquitin-specific protease 15 (USP15) to remove Lys63 (K63)-linked polyubiquitin chains of TBK1 Our findings reveal a role of the UBE2S-USP15-TBK1 axis in the regulation of host antiviral innate immune responses.
IU1 suppresses proliferation of cervical cancer cells through MDM2 degradation
INTERNATIONAL JOURNAL OF BIOLOGICAL SCIENCES
Authors: Xu, Liu; Wang, Jing; Yuan, Xiaoning; Yang, Shuhua; Xu, Xiaolong; Li, Kai; He, Yanqi; Wei, Lei; Zhang, Jingwei; Tian, Yihao
Previous studies have demonstrated that the antitumor potential of IU1 (a pharmacological compound), which was mediated by selective inhibition of proteasome-associated deubiquitinase ubiquitin-specific protease 14 (USP14). However, the underlying molecular mechanisms remain elusive. It has been well established that mdm2 (Murine double minute 2) gene was amplified and/or overexpressed in a variety of human neoplasms, including cervical cancer. Furthermore, MDM2 is critical to cervical cancer development and progression. Relatively studies have reported that USP15 and USP7 stabilized MDM2 protein levels by removing its ubiquitin chain. In the current study, we studied the cell proliferation status after IU1 treatment and the USP14-MDM2 protein interaction in cervical cancer cells. This study experimentally revealed that IU1 treatment reduced MDM2 protein expression in HeLa cervical cancer cells, along with the activation of autophagy-lysosomal protein degradation and promotion of ubiquitin-proteasome system (UPS) function, thereby blocked G0/G1 to S phase transition, decreased cell growth and triggered cell apoptosis. Thus, these results indicate that IU1 treatment simultaneously targets two major intracellular protein degradation systems, ubiquitin-proteasome and autophagy-lysosome systems, which leads to MDM2 degradation and contributes to the antitumor effect of IU1.