P53 Ubiquitination Research Articles

FBXO46 negatively regulates p53 activity by stabilizing Mdm2.

The tumor suppressor p53 plays a central role in suppressing tumor formation. Mouse double minute 2 homolog (Mdm2) serves as the principal ubiquitin E3 ligase responsible for the ubiquitination and subsequent degradation of p53. However, the regulatory mechanisms governing the Mdm2-p53 pathway are not comprehensively understood. Here, we report that F-box only protein 46 (FBXO46) directly binds to Mdm2 and inhibits its self-ubiquitination and degradation, leading to Mdm2 stabilization and subsequent Mdm2-mediated ubiquitination and degradation of p53. Functionally, FBXO46 promotes cell proliferation, accelerates G1/S cell cycle progression, and increases anchorage-independent cell growth by inhibiting p53. Collectively, these findings reveal a critical role for FBXO46 in controlling Mdm2 stability and establish FBXO46 as an important regulator of the Mdm2-p53 pathway.

XAF1 antagonizes TRIM28 activity through the assembly of a ZNF313-mediated destruction complex to suppress tumor malignancy.

X-linked inhibitor of apoptosis-associated factor 1 (XAF1) is a stress-inducible pro-apoptotic protein that is commonly inactivated in multiple human cancers. Nevertheless, the molecular basis for its tumor suppression function remains largely uncharacterized. Here we report that XAF1 antagonizes the oncogenic activity of tripartite motif containing 28 (TRIM28) ubiquitin E3 ligase through zinc finger protein 313 (ZNF313)-induced ubiquitination and proteasomal degradation. XAF1 exerts apoptosis-promoting effect more strongly in TRIM28+/+ versus XAF1-/- tumor cells and suppresses tumor cell growth, migration, invasion, and epithelial-to-mesenchymal transition and xenograft tumor growth in a highly TRIM28-dependent fashion. Mechanistically, XAF1 interacts directly with the RING domains of TRIM28 and ZNF313 through the ZF6 and ZF7 domain, respectively, thereby facilitating ZNF313 interaction with and ubiquitination of TRIM28. A mutant XAF1 lacking either ZF6 or ZF7 domain exhibits no activity to promote TRIM28 ubiquitination. By destabilizing TRIM28, XAF1 blocks TRIM28-driven ubiquitination of p53 and RLIM, p53-HDAC1 interaction, and TWIST1 stabilization. Intriguingly, TRIM28 destabilizes XAF1 through K48-linked polyubiquitination and proteasomal degradation to protect tumor cells from apoptotic stress, indicating its role as an intrinsic antagonist against XAF1 and the antagonistic interplay of XAF1 and TRIM28. XAF1 expression is inversely correlated with TRIM28 expression in cancer cell lines and tumor tissues and more tightly associated with the survival of TRIM28-high versus TRIM28-low patients. Together, this study uncovers a novel mechanism by which XAF1 suppresses tumor malignancy and an important role for XAF1-TRIM28 interplay in governing stress response, illuminating the mechanistic consequence of its alteration during tumorigenic process.

Shenqifuzheng injection inhibits lactic acid-induced cisplatin resistance in NSCLC by affecting FBXO22/p53 axis through FOXO3

HighlightsFOXO3 was decreased, while LA and FBXO22 were increased in NSCLC patients.LA promoted cisplatin resistance in NSCLC in vitro and in vivo.SQFZ inhibited LA-induced cisplatin resistance in NSCLC by regulating FOXO3.FBXO22 affected p53 ubiquitination to reverse the inhibitory effect of SQFZ.SQFZ inhibited cisplatin resistance in NSCLC by FOXO3/FBXO22/p53 axis.

FBXO family genes promotes hepatocellular carcinoma via ubiquitination of p53

FBXO protein family plays an essential role in the ubiquitination process acting as E3 ligases, which may contribute to the progression of cancers. However, the molecular functions of FBXOs in hepatocellular carcinoma (HCC) remain incompletely understood. Here, we investigated the overlapping genes between the FBXOs and differentially expressed genes (DEGs) of HCC identified by utilizing The Cancer Genome Atlas (TCGA) dataset, then, a prognostic model with effective predictive capacity was constructed based on the uni-cox and LASSO regression analyses. To elucidate the underlying mechanism of the FBXO model genes, KEGG analysis was carried out. Drug metabolism-cytochrome P450 and retinol metabolism were revealed as the potential pathway, which Increased the credibility of subsequent drug prediction research. Meanwhile, patients divided by the prognostic model showed a different immune infiltrating status and we also found FBXO model genes may ubiquitinate P53, inducing TP53 more prone to mutations, thereby promoting the occurrence and development of tumors. Consistent with these findings, the result of immunohistochemistry (IHC) validated an elevated expression of these model genes in HCC tissues than in the adjacent tissues. The primary aim of this investigation is to formulate a prognostic model while exploring the underlying mechanisms associated with FBXO genes in HCC. These findings offer initial research perspectives on the involvement of FBXO genes in HCC and contribute to the discovery of dependable biomarkers for the management, prognostication, and early detection of HCC in patients.

Rational design, synthesis, and biophysical characterization of a peptidic MDM2-MDM4 interaction inhibitor

In recent years, the restoration of p53 physiological functions has become an attractive therapeutic approach to develop novel and efficacious cancer therapies. Among other mechanisms, the oncosuppressor protein p53 is functionally regulated by MDM2 through its E3 ligase function. MDM2 promotes p53 ubiquitination and degradation following homodimerization or heterodimerization with MDM4. Recently, we discovered Pep3 (1, Pellegrino et al., 2015), a novel peptidic inhibitor of MDM2 dimerization able to restore p53 oncosuppressive functions both in vitro and in vivo. In this work, we were able to identify the key interactions between peptide 1 and MDM2 RING domain and to design peptide 2, a truncated version of 1 that is still able to bind MDM2. Integrating both computational and biophysical techniques, we show that peptide 2 maintains the conserved peptide 1-MDM2 interactions and is still able to bind to full-length MDM2.

FBXO2 promotes the progression of papillary thyroid carcinoma through the p53 pathway

Emerging evidence have demonstrated that F-box only protein 2 (FBXO2) is intimately associated with malignant tumor development and occurrence. However, neither the functions nor the molecular mechanisms underlying FBXO2 have been determined in the papillary thyroid carcinoma (PTC). The quantitative real-time PCR (qRT-PCR), western blotting and immunohistochemistry were carried out to detect the FBXO2 expression in PTC tissues. CCK-8 assay, EdU assay and flow cytometry were used to assess cell proliferation, cell cycle and apoptosis. The trans-well assay was conducted to determine the cell invasiveness. The effect of FBXO2 on PTC cell proliferation in vivo was observed through a subcutaneous tumor formation experiment in nude mice. Immunoprecipitation were conducted to detect the interaction between FBXO2 and p53. The ubiquitination assays were conducted to assess the regulation of p53 ubiquitination by FBXO2. FBXO2 was overexpressed in both PTC tissues and cell lines. FBXO2 expression positively correlated with PTC tumor size, lymphatic metastasis, and extramembranous invasion. Furthermore, silencing FBXO2 inhibited PTC cell proliferation and promoted apoptosis. The overexpression of FBXO2 significantly promotes PTC cell proliferation. Mechanistic studies revealed that FBXO2 could directly bind to p53 and promote its ubiquitination degradation. Knockdown of p53 partially reversed the progression arrest induced by FBXO2 Knockdown in PTC cells. FBXO2 knockdown inhibited PTC cell proliferation and promoted apoptosis by targeting p53 for ubiquitination and degradation. This process represents a research foundation for its diagnostic and therapeutic applications.

Deletion of ASPP1 in myofibroblasts alleviates myocardial fibrosis by reducing p53 degradation

In the healing process of myocardial infarction, cardiac fibroblasts are activated to produce collagen, leading to adverse remodeling and heart failure. Our previous study showed that ASPP1 promotes cardiomyocyte apoptosis by enhancing the nuclear trafficking of p53. We thus explored the influence of ASPP1 on myocardial fibrosis and the underlying mechanisms. Here, we observed that ASPP1 was increased after 4 weeks of MI. Both global and myofibroblast knockout of ASPP1 in mice mitigated cardiac dysfunction and fibrosis after MI. Strikingly, ASPP1 produced the opposite influence on p53 level and cell fate in cardiac fibroblasts and cardiomyocytes. Knockdown of ASPP1 increased p53 levels and inhibited the activity of cardiac fibroblasts. ASPP1 accumulated in the cytoplasm of fibroblasts while the level of p53 was reduced following TGF-β1 stimulation; however, inhibition of ASPP1 increased the p53 level and promoted p53 nuclear translocation. Mechanistically, ASPP1 is directly bound to deubiquitinase OTUB1, thereby promoting the ubiquitination and degradation of p53, attenuating myofibroblast activity and cardiac fibrosis, and improving heart function after MI.

TERT upregulation promotes cell proliferation via degradation of p21 and increases carcinogenic potential.

Telomerase reverse transcriptase (TERT) gene aberration is detectable in >80% of cases with hepatocellular carcinoma (HCC). TERT reactivation is essential for cellular immortalization because it stabilizes telomere length, although the role of TERT in hepatocarcinogenesis remains unelucidated. To elucidate the significance of aberrant TERT expression in hepatocytes in inflammation-associated hepatocarcinogenesis, we generated Alb-Cre;TertTg mice, which overexpress TERT in the liver and examined their phenotype during chronic inflammation. Based on transcriptome data from the liver tissue of Alb-Cre;TertTg mice, we examined the role of TERT in hepatocarcinogenesis in vitro. We also evaluated the relationship between TERT and cell-cycle-related molecules, including p21, in HCC samples. The liver tumor development rate was increased by TERT overexpression during chronic inflammation, especially in the absence of p53 function. Gene set enrichment analysis of liver tissues revealed that gene sets related to TNF-NFκB signaling, cell cycle, and apoptosis were upregulated in Alb-Cre;TertTg liver. A luciferase reporter assay and immunoprecipitation revealed that TERT interacted with NFκB p65 and enhanced NFκB promoter activity. On the other hand, TERT formed protein complexes with p21, cyclin A2, and cyclin E and promoted ubiquitin-mediated degradation of p21, specifically in the G1 phase. In the clinical HCC samples, TERT was highly expressed but p21 was conversely downregulated, and TERT expression was associated with the upregulation of molecules related to the cell cycle. Taken together, the aberrant upregulation of TERT increased NFκB promoter activity and promoted cell cycle progression via p21 ubiquitination, leading to hepatocarcinogenesis. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

PITAR, a DNA damage-inducible cancer/testis long noncoding RNA, inactivates p53 by binding and stabilizing TRIM28 mRNA.

In tumors with WT p53, alternate mechanisms of p53 inactivation are reported. Here, we have identified a long noncoding RNA, PITAR (p53 Inactivating TRIM28 Associated RNA), as an inhibitor of p53. PITAR is an oncogenic Cancer/testis lncRNA and is highly expressed in glioblastoma (GBM) and glioma stem-like cells (GSC). We establish that TRIM28 mRNA, which encodes a p53-specific E3 ubiquitin ligase, is a direct target of PITAR. PITAR interaction with TRIM28 RNA stabilized TRIM28 mRNA, which resulted in increased TRIM28 protein levels and reduced p53 steady-state levels due to enhanced p53 ubiquitination. DNA damage activated PITAR, in addition to p53, in a p53-independent manner, thus creating an incoherent feedforward loop to inhibit the DNA damage response by p53. While PITAR silencing inhibited the growth of WT p53 containing GSCs in vitro and reduced glioma tumor growth in vivo, its overexpression enhanced the tumor growth in a TRIM28-dependent manner and promoted resistance to Temozolomide. Thus, we establish an alternate way of p53 inactivation by PITAR, which maintains low p53 levels in normal cells and attenuates the DNA damage response by p53. Finally, we propose PITAR as a potential GBM therapeutic target.

LUCAT1 Activates the Malignant Phenotypes of Lung Cancer Cells via Regulating P53 Ubiquitination.

Long non-coding RN (lncRNAs) have been implicated in lung cancer, but the mechanisms stay unclear. We investigated the theatrical role and mechanism of lncRNA Lung cancer associated transcript 1 LUCAT1 in the malignant progress of lung cancer. From May 2022 to March 2023, a total of thirty normal and cancerous tissues were collected from patients diagnosed with non-small cell lung cancer at Zhongke Gengjiu Hospital in Anhui Province, China. The human SPC-A1 and A549 cell lines were chosen as the subjects for the relevant cellular experiments in this study. LncRNAs were expressed in a different manner identified by bioinformatics methods, and the expression levels in lung cancer tissues as well as cells were verified by the qRT-PCR assay. The biological role of LUCAT1 in NSCLC was determined by CCK-8, EdU, and transwell assay. The regulation of ubiquitin of P53 by LUCAT1 was studied, which showed that LUCAT1 was significantly elevated in NSCLC cell lines and patients' tissues (P<0.05). High levels of LUCAT1 promoted the proliferation, invasion, and migration of NSCLC cells. Mechanism studies showed that LUCAT1 was mainly located in the nucleus, which bound to P53 and mediated the ubiquitinated degradation of P53. Meanwhile, LUCAT1 knockdown attenuated the ubiquitination process of P53. In addition, rescue experiments illustrated that LUCAT1 induced the proliferation and invasion of NSCLC cells, and played a key role in the survival and tumorigenicity of NSCLC cells by mediating the ubiquitination of P53. Collectively, LUCAT1 activated the malignant phenotypes of NSCLC cells via regulating P53 ubiquitination, which provided a new idea for the diagnosis and treatment of NSCLC.

SRBD1 Regulates the Cell Cycle, Apoptosis, and M2 Macrophage Polarization via the RPL11-MDM2-p53 Pathway in Glioma.

Low expression of certain ribosomal proteins leads to the inactivation of p53, which is mediated mainly by RPL5 or RPL11 (ribosomal protein L11). It is also unknown what mechanisms drive aberrant ribosomal proteins expression in tumor. SRBD1 (S1 RNA-binding domain 1), as a highly conserved RNA-binding protein, is lowly expressed in glioma tissues and correlated with glioma prognosis. In this study, we observed that SRBD1 was closely related to p53 signaling. The upregulation of SRBD1 elevated p53 levels, thereby activating the p53 signaling pathway. As an RNA bind protein, SRBD1 could bind to the 5'-UTR of target genes and regulate RNA translation. We further conducted RNA immunoprecipitation using anti-SRDB1 antibody and noticed 29 hub RNA, including RPL11. RPL11 could inhibit MDM2-mediated p53 ubiquitination. SRBD1 upregulation promoted RPL11 binding to MDM2 via elevating RPL11 protein levels, which in turn activated the p53 signaling. Disrupting the p53 signaling blocked SRBD1-induced glioma suppression. In mouse xenograft model, SRBD1 ectopic expression was effective in reducing the total M2 tumor-associated macrophages (TAMs) density and suppressed glioma tumor growth. In summary, these data show that SRBD1 has a critical role in inhibition of glioma tumor growth and M2 macrophage polarization, and targeting RPL11-MDM2-p53 signaling may be an effective strategy to improve therapy and survival for glioma patients.

Schisandrol B inhibits calcification of aortic valve by targeting p53 related inflammatory and senescence

Calcific aortic valve disease (CAVD) primarily involves osteogenic differentiation in human aortic valve interstitial cells (hVICs). Schisandrol B (SolB), a natural bioactive constituent, has known therapeutic effects on inflammatory and fibrotic disorders. However, its impact on valve calcification has not been reported. We investigated the effect of SolB on osteogenic differentiation of hVICs. Transcriptome sequencing was used to analyze potential molecular pathways affected by SolB treatment. The study also included an in vivo murine model using aortic valve wire injury surgery to observe SolB's effect on valve calcification. SolB inhibited the osteogenic differentiation of hVICs, reversing the increase in calcified nodule formation and osteogenic proteins. In the murine model, SolB significantly decreased the peak velocity of the aortic valve post-injury and reduced valve fibrosis and calcification. Transcriptome sequencing identified the p53 signaling pathway as a key molecular target of SolB, demonstrating its role as a molecular glue in the mouse double minute 2 (MDM2)-p53 interaction, thereby promoting p53 ubiquitination and degradation, which further inhibited p53-related inflammatory and senescence response. These results highlighted therapeutic potential of SolB for CAVD via inhibiting p53 signaling pathway and revealed a new molecular mechanism of SolB which provided a new insight of theraputic mechanism for CAVD.

Hdm2 disrupts HdmX-mediated nuclear export of p53 by sequestering it in nucleus

Dysfunction of the tumor suppressor p53 occurs in most human cancers, Hdm2 and HdmX play critical roles in p53 inactivation and degradation. Under unstressed conditions, HdmX binds to p53 like Hdm2, but HdmX cannot directly induce p53 degradation. Moreover, HdmX has been reported to stimulate Hdm2-mediated ubiquitination and degradation of p53. Here we reported that HdmX promoted the nuclear export of p53 independent of Hdm2 in living cells using FRET technology. Whereas, Hdm2 impeded HdmX-mediated nuclear export of p53 by sequestering it in nucleus. Interestingly, the C-terminal RING domain mutant Hdm2C464A formed heterooligomers with p53 in nucleus, which was inhibited by HdmX. The heterooligomers were located near PML-NBs. This study indicate that the nuclear Hdm2-HdmX interaction aborts the HdmX-mediated nuclear export of p53.

Novel hypoxia-induced HIF-1αactivation in asthma pathogenesis

BackgroundAsthma’s complexity, marked by airway inflammation and remodeling, is influenced by hypoxic conditions. This study focuses on the role of Hypoxia-Inducible Factor-1 Alpha (HIF-1α) and P53 ubiquitination in asthma exacerbation.MethodsHigh-throughput sequencing and bioinformatics were used to identify genes associated with asthma progression, with an emphasis on GO and KEGG pathway analyses. An asthma mouse model was developed, and airway smooth muscle cells (ASMCs) were isolated to create an in vitro hypoxia model. Cell viability, proliferation, migration, and apoptosis were assessed, along with ELISA and Hematoxylin and Eosin (H&E) staining.ResultsA notable increase in HIF-1α was observed in both in vivo and in vitro asthma models. HIF-1α upregulation enhanced ASMCs’ viability, proliferation, and migration, while reducing apoptosis, primarily via the promotion of P53 ubiquitination through MDM2. In vivo studies showed increased inflammatory cell infiltration and airway structural changes, which were mitigated by the inhibitor IDF-11,774.ConclusionThe study highlights the critical role of the HIF-1α-MDM2-P53 axis in asthma, suggesting its potential as a target for therapeutic interventions. The findings indicate that modulating this pathway could offer new avenues for treating the complex respiratory disorder of asthma.

HADHA promotes glioma progression by accelerating MDM2-mediated p53 ubiquitination.

Glioma represents a notoriously aggressive and malignant tumor that targets the central nervous system, with a poor prognosis for patients. In this research, we set out to examine the role of hydroxyacyl-CoA dehydrogenase trifunctional multienzyme complex subunit alpha (HADHA) in glioma, its clinical significance, as well as its potential biological mechanisms. In this study, we used immunohistochemistry staining to assess the expression level of HADHA in glioma tissues. We also evaluated the correlation between HADHA expression and patient survival using the Kaplan-Meier method. To determine the role of HADHA in glioma cells, we conducted loss-of-function assays in vitro and in vivo. Additionally, we utilized co-immunoprecipitation and protein stability assays to investigate the potential mechanisms involving HADHA, MDM2, and p53 in glioma. Our research findings indicate that gliomas exhibit high levels of HADHA. Clinically, high expression of HADHA suggests an increased risk of malignant tumors, recurrence, and reduced survival rates. Functionally, knocking down HADHA can lead to decreased proliferation, enhanced apoptosis, and inhibited migration of glioma cells. Mechanistically, HADHA accelerates MDM2-mediated p53 ubiquitination through interaction with MDM2. Consistently, MDM2 knockdown or overexpression of p53 can attenuate the promoting effect of HADHA overexpression on the malignant progression of glioma. We have discovered a novel role of HADHA in promoting MDM2-mediated p53 ubiquitination, which contributes to the progression of glioma. This finding provides a new perspective to understand the pathogenesis of glioma and offers a potential target for developing innovative therapeutic strategies.

UBE2D1 promotes glioblastoma proliferation by modulating p21 ubiquitination.

Glioblastoma (GBM) cells exhibit aberrant proliferative abilities and resistance to conventional therapies. However, the mechanisms underlying these malignant phenotypes are poorly understood. In this study, we identified ubiquitin-conjugating enzyme E2D1 (UBE2D1) as a crucial stimulator of GBM development. It is highly expressed in GBM and closely associated with poor prognosis in patients with GBM. UBE2D1 knockdown inhibits GBM cell growth and leads to G1 cell cycle arrest. Mechanistically, UBCH5A binds to p21 at the protein level and induces the ubiquitination and degradation of p21. This negative regulation is mediated by STUB1. Our findings are the first to identify UBE2D1 as a key driver of GBM growth and provide a potential target for improving prognosis and therapy.

Synthesis, characterization, and anti-cancer potential of novel p53-mediated Mdm2 and Pirh2 modulators: an integrated In silico and In vitro approach.

Introduction: Leukemia is a global health concern that requires alternative treatments due to the limitations of the FDA-approved drugs. Our focus is on p53, a crucial tumor suppressor that regulates cell division. It appears possible to stabilize p53 without causing damage to DNA by investigating dual-acting inhibitors that target both ligases. The paper aims to identify small molecule modulators of Mdm2 and Pirh2 by using 3D structural models of p53 residues and to further carry out the synthesis and evaluation of hit candidates for anti-cancer potency by in vitro and in silico studies. Methods: We synthesized structural analogues of MMs02943764 and MMs03738126 using a 4,5-(substituted) 1,2,4-triazole-3-thiols with 2-chloro N-phenylacetamide in acetone with derivatives of PAA and PCA were followed. Cytotoxicity assays, including MTT, Trypan Blue Exclusion, and MTS assays, were performed on cancer cell lines. Anti-proliferation activity was evaluated using K562 cells. Cell cycle analysis and protein expression studies of p53, Mdm2, and Pirh2 were conducted using flow cytometry. Results: As for results obtained from our previous studies MMs02943764, and MMs03738126 were selected among the best-fit hit molecules whose structural analogues were further subjected to molecular docking and dynamic simulation. Synthesized compounds exhibited potent anti-proliferative effects, with PAC showing significant cytotoxicity against leukemia cells. PAC induced cell cycle arrest and modulated p53, Mdm2, and Pirh2 protein expressions in K562 cells. Molecular docking revealed strong binding affinity of PAC to p53 protein, further confirmed by molecular dynamics simulation. Discussion: The study presents novel anticancer compounds targeting the p53 ubiquitination pathway, exemplified by PAC. Future perspectives involve further optimization and preclinical studies to validate PAC's potential as an effective anticancer therapy.

Post-Translational Modifications (PTMs) of mutp53 and Epigenetic Changes Induced by mutp53.

Wild-type (wt) p53 and mutant forms (mutp53) play a key but opposite role in carcinogenesis. wtP53 acts as an oncosuppressor, preventing oncogenic transformation, while mutp53, which loses this property, may instead favor this process. This suggests that a better understanding of the mechanisms activating wtp53 while inhibiting mutp53 may help to design more effective anti-cancer treatments. In this review, we examine possible PTMs with which both wt- and mutp53 can be decorated and discuss how their manipulation could represent a possible strategy to control the stability and function of these proteins, focusing in particular on mutp53. The impact of ubiquitination, phosphorylation, acetylation, and methylation of p53, in the context of several solid and hematologic cancers, will be discussed. Finally, we will describe some of the recent studies reporting that wt- and mutp53 may influence the expression and activity of enzymes responsible for epigenetic changes such as acetylation, methylation, and microRNA regulation and the possible consequences of such changes.

Ubiquitination of p21 by E3 ligase RNF135 promotes the proliferation of human glioblastoma cells.

Glioblastoma multiforme (GBM) is a highly heterogeneous tumor of the central nervous system with a high mortality rate. The upregulation of RING finger protein 135 (RNF135), an E3 ligase, has been observed in GBM, but the associated mechanisms have not been fully elucidated. The aim of the present study was to identify the substrate of RNF135 and study its functions in GBM. Bioinformatics analyses were performed. In addition, RNF135 was overexpressed or knocked down in human U87 and U251 GBM cells, and the effect on cell proliferation was analyzed using Cell Counting Kit-8 and colony formation assays. Furthermore, the interaction of RNF135 with its potential substrate was analyzed using glutathione S-transferase, yeast two-hybrid, immunoprecipitation (IP), co-IP and immunoblotting assays. Bioinformatics analysis indicated that RNF135 serves as a marker of poor prognosis in GBM. The overexpression of RNF135 was demonstrated to promote the proliferation of GBM cells, while the knockdown of RNF135 inhibited GBM cell growth. In addition, the results of the interaction experiments indicate that RNF135 interacts with p21 and mediates the degradation of p21 by ubiquitination. The major site of RNF135-mediated p21 ubiquitination was identified as K163. Further experiments demonstrated that RNF135 promotes the proliferation of GBM cells mainly via p21. In summary, these findings suggest that RNF135 has potential as a therapeutic target for the treatment of GBM.

ZBTB7A interferes with the RPL5-P53 feedback loop and reduces endoplasmic reticulum stress-induced apoptosis of pancreatic cancer cells.

Endoplasmic reticulum (ER) stress is a primary mechanism leading to cell apoptosis, making it of great research interests in cancer management. This study delves into the function of ribosomal protein L5 (RPL5) in ER stress within pancreatic cancer (PCa) cells and investigates its regulatory mechanisms. Bioinformatics predictions pinpointed RPL5 as an ER stress-related gene exhibiting diminished expression in PCa. Indeed, RPL5 was found to be poorly expressed in PCa tissues and cells, with this reduced expression correlating with an unfavorable prognosis. Moreover, RPL5 overexpression led to heightened levels of p-PERK, p-eIF2α, and CHOP, bolstering the proapoptotic effect of Tunicamycin, an ER stress activator, on PCa cells. Additionally, the RPL5 overexpression curbed cell proliferation, migration, and invasion. Tunicamycin enhanced the binding between RPL5 and murine double minute 2 (MDM2), thus suppressing MDM2-mediated ubiquitination and degradation of P53. Consequently, P53 augmentation intensified ER stress, which further enhanced the binding between RPL5 and MDM2 through PERK-dependent eIF2α phosphorylation, thereby establishing a positive feedback loop. Zinc finger and BTB domain containing 7A (ZBTB7A), conspicuously overexpressed in PCa samples, repressed RPL5 transcription, thereby reducing P53 expression. Silencing of ZBTB7A heightened ER stress and subdued the malignant attributes of PCa cells, effects counteracted upon RPL5 silencing. Analogous outcomes were recapitulated in vivo employing a xenograft tumor mouse model, where ZBTB7A silencing dampened the tumorigenic potential of PCa cells, an effect reversed by additional RPL5 silencing. In conclusion, this study suggests that ZBTB7A represses RPL5 transcription, thus impeding the RPL5-P53 feedback loop and mitigating ER-induced apoptosis in PCa cells.