Effect of knockout (KO) of Usp28 on gene expression in embryonic stem cells(ESCs) cultured under 2iL condition
Ontology highlight
ABSTRACT: For validating the role Usp28 in regulating mouse ESC self-renewal, sgRNAs were designed to generate Usp28 KO cell lines. We then performed gene expression profiling analysis using data obtained from RNA-seq control (CTL) and Usp28 KO ESCs.
Project description:Usp28-KO HLF cell lines were generated by CRISPR-Cas9. Usp28-KO cells expressing Usp28-WT, Usp28-Mono or a control vector were established by lentiviral transduction.
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: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:SREBP2 controls the expression of enzymes involved in the mevalonate pathway (MVP), a biosynthetic process that drives the synthesis of dolichol, heme A, ubiquinone and cholesterol but also provides substrates for protein prenylation, and that is frequently deregulated in cancer. We show here that SREBP2 is a novel substrate for the deubiquitinating enzyme USP28 and that USP28 regulates SREBP2 stability independent of FBXW7. Inhibition of USP28 reduces MVP activity and renders cancer cells highly sensitive to MVP inhibition by statins. Moreover, statin sensitivity of USP28 depleted cells was rescued by the addition of geranyl-geranyl-pyrophosphate, a substrate for protein prenylation. We also provide evidence that SREBP2 participates in the regulation of gene expression signature associated with squamous cell carcinoma (SCC) and that SREBP2 and enzymes of the MVP are overexpressed in SCC from different tissue origins. Finally, deletion of SREBP2 attenuated tumour growth in a mouse model of lung cancer. Our findings suggest that SREBP2 is a novel substrate for USP28 and that combinatorial targeting of the MVP together with USP28 inhibition could be a therapeutic strategy for the treatment of squamous cell carcinomas.
Project description:The oncoprotein ∆Np63 is an essential transcriptional master- and cell identity regulator in squamous cell carcinoma (SCC) of various origins, encompassing lung, head and neck, oesophagus, cervix and skin. While in non-transformed cells ∆Np63 protein abundance is tightly regulated by the ubiquitin proteasome system (UPS), in tumours E3-ligases ubiquitylating ∆Np63, such as FBXW7, are commonly mutated or lost, resulting in a hyper-stabilisation of the oncogenic driver. Targeting ∆Np63 protein abundance in SCC could present a possible therapeutic avenue. Here, we report that the deubiquitylase USP28 regulates ∆Np63 protein stability and abundance in SCC by counteracting the degradative UPS system. Interference with USP28 activity by pharmacological inhibition specifically affected human SCC cell lines and, finally, we were able to demonstrate in vivo using CRISPR/Cas9 mouse models that Usp28 is required for SCC induction and maintenance. Hence, targeting USP28 is a viable option to tackle ∆Np63 protein abundance in SCC tumours.
Project description:The majority of diabetics are susceptible to cardiac dysfunction and heart failure, while conventional drug therapy cannot correct diabetic cardiomyopathy (DCM) progression. Herein, we assessed the potential role and therapeutic value of ubiquitin-specific protease 28 (USP28) on the metabolic vulnerability of DCM. cardiac USP28 deficient diabetic mice showed cardiac dysfunction, lipid accumulation, and mitochondrial disarrangement, compared to their controls. Conversely, USP28 overexpression improved systolic and diastolic dysfunction and ameliorated cardiac hypertrophy and fibrosis in the diabetic heart. Mechanistically, USP28 directly interacted with peroxisome proliferator-activated receptor α (PPARα), deubiquitinating and stabilizing PPARα (Lys152) to promote mitofusin 2 (Mfn2) transcription, thereby impeding mitochondrial morphofunctional defects.
Project description:The oncogenic transcription factor Myc is a pleiotropic regulator of RNA Polymerase II (RNAPII)-dependent transcription, DNA replication and DNA damage response pathways. Myc is stringently regulated by the ubiquitin system - for example, ubiquitination controls recruitment of the elongation factor Paf1c, which is critical for several Myc functions. Curiously, a key Myc-targeting deubiquitinase Usp28 also controls cellular response to DNA damage via the mediator protein 53bp1. Usp28 forms stable dimers, but the biological role of Usp28 dimerization is unknown. We show that dimerization limits Usp28 activity and restricts recruitment of Paf1c by Myc. Expression of monomeric Usp28 leads to ectopic Paf1c recruitment and resolution of transcription-replication conflicts, accelerating DNA synthesis. Strikingly, 53bp1 selectively interacts with and stabilizes dimeric Usp28 - depletion of 53bp1 favors formation of Usp28 monomers deregulating DNA replication. Genotoxic stress disrupts 53bp1-Usp28 complexes, promotes formation of Usp28 monomers and recruitment of Paf1 by Myc. This triggers ectopic DNA synthesis during early response to genotoxins, amplifying DNA damage. We propose that dimerization of Usp28 limits aberrant replication at transcriptionally active chromatin to maintain genome stability.
Project description:The majority of diabetics are susceptible to cardiac dysfunction and heart failure, while conventional drug therapy cannot correct diabetic cardiomyopathy (DCM) progression. Herein, we assessed the potential role and therapeutic value of ubiquitin-specific protease 28 (USP28) on the metabolic vulnerability of DCM. PPARα-/- in the db/db background mice were constructed to check the mechanism of USP28 in vivo. Inducible cardiac-specific deletion of Mfn2 in the db/db background mice was utilized to evaluate USP28-mediated cardioprotection. chromatin immunoprecipitation (ChIP) assays revealed that PPARα promote mitofusin 2 (Mfn2) transcription, thereby impeding mitochondrial morphofunctional defects.