Cop1 constitutively regulates c-Jun protein stability and functions as a tumor suppressor in mice
Domenico Migliorini, … , William C. Skarnes, Jean-Christophe Marine
Domenico Migliorini, … , William C. Skarnes, Jean-Christophe Marine
Published March 14, 2011
Citation Information: J Clin Invest. 2011;121(4):1329-1343. https://doi.org/10.1172/JCI45784.
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Research Article

Cop1 constitutively regulates c-Jun protein stability and functions as a tumor suppressor in mice

Abstract

Biochemical studies have suggested conflicting roles for the E3 ubiquitin ligase constitutive photomorphogenesis protein 1 (Cop1; also known as Rfwd2) in tumorigenesis, providing evidence for both the oncoprotein c-Jun and the tumor suppressor p53 as its targets. Here we present what we believe to be the first in vivo investigation of the role of Cop1 in cancer etiology. Using an innovative genetic approach to generate an allelic series of Cop1, we found that Cop1 hypomorphic mice spontaneously developed malignancy at a high frequency in the first year of life and were highly susceptible to radiation-induced lymphomagenesis. Further analysis revealed that c-Jun was a key physiological target for Cop1 and that Cop1 constitutively kept c-Jun at low levels in vivo and thereby modulated c-Jun/AP-1 transcriptional activity. Importantly, Cop1 deficiency stimulated cell proliferation in a c-Jun–dependent manner. Focal deletions of COP1 were observed at significant frequency across several cancer types, and COP1 loss was determined to be one of the mechanisms leading to c-Jun upregulation in human cancer. We therefore conclude that Cop1 is a tumor suppressor that functions, at least in part, by antagonizing c-Jun oncogenic activity. In the absence of evidence for a genetic interaction between Cop1 and p53, our data strongly argue against the use of Cop1-inhibitory drugs for cancer therapy.

Authors

Domenico Migliorini, Sven Bogaerts, Dieter Defever, Rajesh Vyas, Geertrui Denecker, Enrico Radaelli, Aleksandra Zwolinska, Vanessa Depaepe, Tino Hochepied, William C. Skarnes, Jean-Christophe Marine

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Figure 4

Cop1 deficiency stimulates cell proliferation in a c-Jun–dependent manner.

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Cop1 deficiency stimulates cell proliferation in a c-Jun–dependent mann...
(A–H) All experiments described were performed with cells lacking p53. (A) Growth curve of Cop1+/+ and Cop1hypo/– MEFs; cells were seeded in triplicate at 2 × 105 cells/60-mm dish. The numbers refer to the mean values ± SD of 2 independent MEF cultures. (B) Growth curves of MEFs infected with recombinant retroviruses (pBABE) encoding c-Jun or puromycin resistance only. Cells were seeded in triplicate at 2 × 105 cells/60-mm dish. The numbers refer to the mean values ± SD of 2 independently infected MEF cultures. (C) Samples from B were analyzed by Western blotting. (D) Growth curves of cells expressing shRNAmir–c-Jun (shJun) or shRNAmir-scramble (Ctr). Cells were seeded in triplicate at 2 × 105 cells/60-mm dish. The numbers refer to the mean values ± SD of 2 independently infected MEF cultures. (E) Colony assays were performed with cells expressing shRNAmir–c-Jun or shRNAmir-scramble (Ctr). Data are presented relative to the number of colonies obtained in the Cop1hypo/– cultures infected with the control shRNA, which is set to 1. The numbers refer to the mean values ± SD of 2 independently infected MEF cultures. (F) Samples from D and E were analyzed by Western blotting. (G) Growth curve of Cop1+/+ and Cop1hypo/– MEFs exposed to 10 μM SP600125; cells were seeded in triplicate at 105 cells/100-mm dish. The numbers refer to the mean values ± SD of 2 independent MEF cultures. (H) Colony assays using cells from A, B, and G.