Project description:Fbw7, the substrate recognition subunit of SCF(Fbw7) ubiquitin ligase, mediates turnover of multiple proto-oncoproteins and promotes its own degradation. Fbw7-mediated substrate degradation is antagonized by the Usp28 deubiquitinase. We now show, using knockout mice, that Usp28 preferentially deubiquitinates and stabilizes Fbw7. Monoallelic deletion of Usp28 maintains stable Fbw7 but destabilizes Fbw7 substrates. In contrast, complete knockout of Usp28 promotes Pin1-dependent autocatalytic turnover of Fbw7, accumulation of Fbw7 substrates and oncogenic transformation. Overexpression of Usp28 stabilizes both Fbw7 and its substrates and similarly enhances transformation. We propose that dual regulation of Fbw7 activity by Usp28 maintains physiological levels of Fbw7 substrates, and that both loss and overexpression of Usp28 in human cancer promote Fbw7 substrate accumulation.
Project description:Fbw7, the substrate recognition subunit of SCF(Fbw7) ubiquitin ligase, mediates turnover of multiple proto-oncoproteins and promotes its own degradation. Fbw7-mediated substrate degradation is antagonized by the Usp28 deubiquitinase. We now show, using knockout mice, that Usp28 preferentially deubiquitinates and stabilizes Fbw7. Monoallelic deletion of Usp28 maintains stable Fbw7 but destabilizes Fbw7 substrates. In contrast, complete knockout of Usp28 promotes Pin1-dependent autocatalytic turnover of Fbw7, accumulation of Fbw7 substrates and oncogenic transformation. Overexpression of Usp28 stabilizes both Fbw7 and its substrates and similarly enhances transformation. We propose that dual regulation of Fbw7 activity by Usp28 maintains physiological levels of Fbw7 substrates, and that both loss and overexpression of Usp28 in human cancer promote Fbw7 substrate accumulation. RNAseq experiments of E13.5 murine embryonic fibroblasts (MEFs) derived from animals in which Usp28 was either deleted (-/-), wildtype (+/+) or heterozygous (+/-). In a first set of experiments immortalized MEFs of all three genotypes were analysed in biological triplicates. In a second set of experiments immortalized and Ras transformed MEFs of all three genotypes and MEFs which overexpress USP28 (+/+/+) where sequenced in duplicates.
Project description:We found that BAP1 (BRCA1 Associated Protein-1) shows loss of heterozygosity in over 25% of pancreatic cancer patients and functions as tumor suppressor. Conditional deletion of Bap1 in murine pancreas led to genomic instability, accumulation of DNA damage, and an inflammatory response that evolved to pancreatitis with full penetrance. Concomitant expression of oncogenic KrasG12D led to malignant transformation and development of invasive and metastatic pancreatic cancer. At the molecular level, BAP1 maintains the integrity of the exocrine pancreas by regulating genomic stability and its loss confers sensitivity to radio- and platinum-based therapies.
Project description:Fbw7 is one of the most highly mutated tumor suppressor genes in human cancers. Several Fbw7 mutation types have been found in cancers (e.g. Fbw7Arg/+, other missense mutations and Fbw7-/-). Fbw7Arg/+ missense mutation is the most commonly observed mutation type, however the tumorigenic mechanisms led by Fbw7Arg/+ are as of yet poorly understood. Fbw7 targets almost thirty proteins to degradation, out of many are transcription factors. We performed an integrative study to understand global transcriptional regulation by Fbw7. We investigated the deregulation of two well-studied oncogenic Fbw7 substrates: cMyc and cJun in wild-type and Fbw7 mutant colorectal cancer cell lines and neural stem cells. Our study revealed context-specific transcriptional regulation by Fbw7.
Project description:Fbw7 is one of the most highly mutated tumor suppressor genes in human cancers. Several Fbw7 mutation types have been found in cancers (e.g. Fbw7Arg/+, other missense mutations and Fbw7-/-). Fbw7Arg/+ missense mutation is the most commonly observed mutation type, however the tumorigenic mechanisms led by Fbw7Arg/+ are as of yet poorly understood. Fbw7 targets almost thirty proteins to degradation, out of many are transcription factors. We performed an integrative study to understand global transcriptional regulation by Fbw7. We investigated the deregulation of two well-studied oncogenic Fbw7 substrates: cMyc and cJun in wild-type and Fbw7 mutant colorectal cancer cell lines and neural stem cells. Our study revealed context-specific transcriptional regulation by Fbw7.