The carboxyl terminus of Hsp70-interacting protein (CHIP) acts as a ubiquitin E3 ligase and a link between the chaperones Hsp70/90 and the proteasome system, playing a vital role in maintaining protein homeostasis. CHIP regulates a number of proteins involved in a myriad of physiological and pathological processes, but the underlying mechanism of action via posttranslational modification has not been extensively explored. In this study, we investigated a novel modulatory mode of CHIP and its effect on CHIP enzymatic activity. ISG15, an ubiquitin-like modifier, is induced by type I interferon (IFN) stimulation and can be conjugated to target proteins (ISGylation). Here we demonstrated that CHIP may be a novel target of ISGylation in HEK293 cells stimulated with type I IFN. We also found that Lys143/144/145 and Lys287 residues in CHIP are important for and target residues of ISGylation. Moreover, ISGylation promotes the E3 ubiquitin ligase activity of CHIP, subsequently causing a decrease in levels of oncogenic c-Myc, one of its many ubiquitination targets, in A549 lung cancer cells and inhibiting A549 cell and tumor growth. In conclusion, the present study demonstrates that covalent ISG15 conjugation produces a novel CHIP regulatory mode that enhances the tumor-suppressive activity of CHIP, thereby contributing to the antitumor effect of type I IFN.
Bibliographical noteFunding Information:
This work was supported by grants from the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2014M3C7A1064545 to K.C.C.) and from the Korea Healthcare Technology R&D Project through the Korea Health Industry Development Institute (KHIDI) funded by the Ministry of Health & Welfare (HI17C0936 to K.C.C.), Republic of Korea. This work was also supported in part by the NRF grant (2015R1A2A2A01003080 to K.C.C.) and by the Yonsei University Future-leading Research Initiative of 2015 (2015-22-0055 to K.C.C.).
All Science Journal Classification (ASJC) codes
- Cellular and Molecular Neuroscience
- Cell Biology
- Cancer Research