TY  - JOUR
A1  - Schülein-Völk, Christina
A1  - Wolf, Elmar
A1  - Zhu, Jing
A1  - Xu, Wenshan
A1  - Taranets, Lyudmyla
A1  - Hellmann, Andreas
A1  - Jänicke, Laura A.
A1  - Diefenbacher, Markus E.
A1  - Behrens, Axel
A1  - Eilers, Martin
A1  - Popov, Nikita
T1  - Dual Regulation of Fbw7 Function and Oncogenic Transformation by Usp28
JF  - CELL REPORTS
N2  - Fbw7, the substrate recognition subunit of SCF(Fbw7) ubiquitin ligase, mediates the turnover of multiple proto-oncoproteins and promotes its own degradation. Fbw7-dependent substrate ubiquitination is antagonized by the Usp28 deubiquitinase. Here, we show that Usp28 preferentially antagonizes autocatalytic ubiquitination and stabilizes Fbw7, resulting in dose-dependent effects in Usp28 knockout mice. Monoallelic deletion of Usp28 maintains stable Fbw7 but drives Fbw7 substrate degradation. In contrast, complete knockout triggers Fbw7 degradation and leads to the accumulation of Fbw7 substrates in several tissues and embryonic fibroblasts. On the other hand, overexpression of Usp28 stabilizes both Fbw7 and its substrates. Consequently, both complete loss and ectopic expression of Usp28 promote Ras-driven oncogenic transformation. We propose that dual regulation of Fbw7 activity by Usp28 is a safeguard mechanism for maintaining physiological levels of proto-oncogenic Fbw7 substrates, which is equivalently disrupted by loss or overexpression of Usp28.
KW  - Fbw7
KW  - oncogenic transformation
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-118219
SN  - 2211-1247
N1  - The sequencing data have been submitted to the GEO repository under accession number GSE59354.
VL  - 9
IS  - 3
ER  - 
TY  - JOUR
A1  - Peter, Stefanie
A1  - Bultinck, Jennyfer
A1  - Myant, Kevin
A1  - Jaenicke, Laura A.
A1  - Walz, Susanne
A1  - Müller, Judith
A1  - Gmachl, Michael
A1  - Treu, Matthias
A1  - Boehmelt, Guido
A1  - Ade, Casten P.
A1  - Schmitz, Werner
A1  - Wiegering, Armin
A1  - Otto, Christoph
A1  - Popov, Nikita
A1  - Sansom, Owen
A1  - Kraut, Norbert
A1  - Eilers, Martin
T1  - H Tumor cell-specific inhibition of MYC function using small molecule inhibitors of the HUWE1 ubiquitin ligase
JF  - EMBO Molecular Medicine
N2  - Deregulated expression of MYC is a driver of colorectal carcinogenesis, necessitating novel strategies to inhibit MYC function. The ubiquitin ligase HUWE1 (HECTH9, ARF-BP1, MULE) associates with both MYC and the MYC-associated protein MIZ1. We show here that HUWE1 is required for growth of colorectal cancer cells in culture and in orthotopic xenograft models. Using high-throughput screening, we identify small molecule inhibitors of HUWE1, which inhibit MYC-dependent transactivation in colorectal cancer cells, but not in stem and normal colon epithelial cells. Inhibition of HUWE1 stabilizes MIZ1. MIZ1 globally accumulates on MYC target genes and contributes to repression of MYC-activated target genes upon HUWE1 inhibition. Our data show that transcriptional activation by MYC in colon cancer cells requires the continuous degradation of MIZ1 and identify a novel principle that allows for inhibition of MYC function in tumor cells.
KW  - colorectal cancer
KW  - HUWE1
KW  - MIZ1
KW  - MYC
KW  - ubiquitination
KW  - cancer
KW  - digestive system
KW  - pharmacology
KW  - drug discovery
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-118132
SN  - 1757-4684
VL  - 6
IS  - 12
ER  -