FBXO38 Ubiquitin Ligase Controls Centromere Integrity via ZXDA/B Stability.
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ABSTRACT:
SUBMITTER: Dibus N
PROVIDER: S-EPMC9260856 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The ubiquitin ligase SCFFBXO38 controls centromeric chromatin by promoting the degradation of the ZXDB protein. To determine the importance of this pathway during development, Fbxo38-deficient mice were generated. The loss of FBXO38 resulted in growth retardation affecting several organs, including the male reproductive system. A detailed analysis of the mutant testes revealed pathological changes in the seminiferous tubules, accompanied by a significant decrease in sperm production and reduced fertility. In adult testes, FBXO38 was specifically expressed in Sertoli cells, a somatic population essential for spermatogenesis initiation and progression. Sertoli cells lacking FBXO38 exhibited stabilized ZXDB protein and upregulated centromeric chromatin. Furthermore, the gene expression profile revealed that the absence of FBXO38 led to a defect in Sertoli cell maturation, specifically characterized by dysregulation in genes controlling retinoic acid metabolism and intercellular communication. Consequently, we documented significant changes in their ability to initiate spermatogonial differentiation. In conclusion, we show that FBXO38 acts as a Sertoli cell maturation factor, affecting the Sertoli cell transcription program, centromere integrity, and, subsequently, the ability to control spermatogenesis.
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Project description:PLAGL2 (Pleomorphic Adenoma Gene Like 2) is an oncoprotein involved in various malignancies including lipoblastomas, hepatoblastomas, and acute myeloid leukemia. Although PLAGL2 is known to mainly act as a transcription factor, other functions which may contribute to its oncogenic potential are not clear. Pirh2 (P53 induced RING-H2 protein) is a p53 inducible E3 ligase involved in the ubiquitination of p53, while the mechanisms to regulate its activities are largely unknown. In this study, we show for the first time that Pirh2 forms dimers through its N- and C-terminus in cells and Pirh2 dimers interact with PLAGL2. The interaction between PLAGL2 and Pirh2 dimers prevents proteasomal degradation of Pirh2. This study thus uncovers a novel function of PLAGL2 as an oncoprotein through regulating the stability of Pirh2. Given the importance of Pirh2 in regulating p53 stability, its interaction with PLAGL2 may provide valuable therapeutic targets in treating Pirh2-overexpression malignancies.
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Project description:CUL9 is a member of the cullin family of E3 ubiquitin ligases, and it localizes predominantly in the cytoplasm. Deletion of Cul9 in mice results in increased DNA damage, widespread aneuploidy, spontaneous tumor development, accelerated Eμ-Myc-induced lymphomagenesis and susceptibility to carcinogenesis. CUL9 binds to p53 and causes cell apoptosis when ectopically expressed. Whether the function of CUL9 in maintaining genomic integrity and suppressing tumorigenesis is linked to p53 has not been genetically tested. Here we report that deletion of CUL9 in human cells results in attenuated p21 induction and impaired cellular response to DNA damage. We show that disruption of Cul9-p53 binding in mouse embryo fibroblasts (MEFs) by a knock-in mutation in Cul9 (Δp53) increases S-phase cell population, accumulates DNA damage during DNA replication and decreases apoptosis to both endogenous and exogenous DNA-damaging agents. The extent of these alterations in Cul9Δp53 MEFs is indistinguishable to those seen in Cul9-/- MEFs and comparable to those seen in p53-/- MEFs. Deletion of CUL9 in p53 null cells does not lead to further increase of DNA damages. Both Cul9-/- and Cul9Δp53 MEFs proliferate faster and undergo spontaneous immortalization while retaining both Arf and p53. These results demonstrate that the functions of CUL9 in regulating cell proliferation and maintaining genomic integrity are mainly mediated by p53, and that CUL9 is a critical p53 activator.
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Project description:Nur77 is a member of the NR4A subfamily of nuclear receptors and has been shown to regulate various biological processes such as apoptosis and inflammation. Here, we show that Nur77 ubiquitination is mediated by the tripartite motif 13 (Trim13), a RING-type E3 ubiquitin ligase. The interaction between Nur77 and Trim13 was confirmed by co-immunoprecipitation. Moreover, we found that Lys539 in Nur77 ubiquitination is targeted for Trim13, which leads to Nur77 degradation. The Trim13-mediated ubiquitination of Nur77 was optimal in the presence of the E2 enzyme UbcH5. Importantly, in addition to Trim13-mediated ubiquitination, the stability of Nur77 was also regulated by casein kinase 2α (CK2α). Pharmacological inhibition of CK2 markedly increased Nur77 levels, whereas overexpression of CK2α, but not its inactive mutant, dramatically decreased Nur77 levels by promoting Nur77 ubiquitination. CK2α phosphorylated Ser154 in Nur77 and thereby regulated Nur77 protein levels by promoting its ubiquitin-mediated degradation. Importantly, we also show that degradation of Nur77 is involved in TNFα-mediated IL-6 production via CK2α and Trim13. Taken together, these results suggest that the sequential phosphorylation and ubiquitination of Nur77 controls its degradation, and provide a therapeutic approach for regulating Nur77 activity through the CK2α-Trim13 axis as a mechanism to control the inflammatory response.
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Project description:Proper centromere function is critical to maintain genomic stability and to prevent aneuploidy, a hallmark of tumors and birth defects. A conserved feature of all eukaryotic centromeres is an essential histone H3 variant called CENP-A that requires a centromere targeting domain (CATD) for its localization. Although proteolysis prevents CENP-A from mislocalizing to euchromatin, regulatory factors have not been identified. Here, we identify an E3 ubiquitin ligase called Psh1 that leads to the degradation of Cse4, the budding yeast CENP-A homolog. Cse4 overexpression is toxic to psh1? cells and results in euchromatic localization. Strikingly, the Cse4 CATD is a key regulator of its stability and helps Psh1 discriminate Cse4 from histone H3. Taken together, we propose that the CATD has a previously unknown role in maintaining the exclusive localization of Cse4 by preventing its mislocalization to euchromatin via Psh1-mediated degradation.
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Project description:Natural killer (NK) cells are the main innate antitumor effector cells and can be constrained in the tumor microenvironment (TME). It has been reported that E3 ligase FBXO38 accelerates PD-1 degradation of tumor-infiltrating T cells to unleash their cytotoxic function. In this study, we found that FBXO38 transcripts were significantly lower in intra-tumoral NK cells than in peri-tumoral regions using specimens from cancer patients in The Cancer Genome Atlas (TCGA). Conditional knock-out (cKO) of FBXO38 in NK cells accelerated tumor growth and increased tumor metastasis. However, FBXO38 deficiency did not show an effect on the cytotoxic function of tumor-infiltrating NK (TINK) cells, but decreased proliferation and survival of TINK cells. Mechanically, FBXO38 deficiency led to TINK cell hyporesponsiveness to IL-15 by reducing the expression of IL-15Rβ and IL-15Rγc, which accounted for the reduced expansion of FBXO38-deficient TINK cells in TME. Furthermore, human NK-92 cells proliferated more rapidly when FBXO38 was overexpressed and exerted greater antitumor efficacy in xenograft mouse models. Conversely, the removal of FBXO38 led to a dramatic decrease in NK-92 cell proliferation. In conclusion, our results suggest that FBXO38 strongly sustains NK cell expansion in the antitumor immunity response.
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