TL;DR
Insight is provided into IRES-mediated translation of Δ160p53, which can be considered a novel target for cancer treatment and its role in cancer regulation.
The transcription factor p63 is indispensable for epithelial stem cell proliferation/differentiation and epidermal development, with alterations in the p63 pathway underlying a subset of ectodermal dysplasias. Despite its critical role, the mechanisms regulating p63 expression remain poorly understood. Here, we identify an m6A‐mediated posttranscriptional mechanism controlling the expression of ΔNp63, the predominant functional p63 isoform in epidermal basal cells. We found that Cre‐mediated conditional deletion of Mettl16, encoding a conserved m6A methyltransferase, in mouse epithelial basal cells caused severe skin developmental abnormalities, reminiscent of human ectodermal dysplasias. RNA sequencing revealed significant downregulation of ΔNp63 and its target genes in Mettl16‐deficient skin, which linked METTL16 to p63 pathways. Mechanistically, we demonstrated that METTL16 directly binds to ΔNp63 mRNA to mediate its m6A modification; this modified ΔNp63 mRNA is subsequently recognized by the m6A reader IGF2BP2, which stabilizes ΔNp63 mRNA and thereby modulates its protein levels. Critically, restoration of ΔNp63 expression mitigated the epidermal defects in Mettl16‐deficient mice. Collectively, our findings uncover a novel METTL16‐m6A‐IGF2BP2‐ΔNp63 regulatory axis governing epidermal development, providing insights into the etiology of ectodermal dysplasias.
Post-transcriptional regulation of gene expression has emerged as a fundamental determinant of cancer initiation, progression, and therapeutic response. Among the RNA-binding proteins (RBPs) involved in mRNA turnover and translational regulation, tristetraprolin (TTP), encoded by the ZFP36 gene, and “Human antigen R” (HuR), encoded by ELAVL1, represent two functionally antagonistic regulators of AU-rich element (ARE)-containing transcripts. TTP promotes the degradation of target mRNAs through recruitment of deadenylation and decay complexes, whereas HuR generally stabilizes and enhances the translation of overlapping mRNA subsets. Because many oncogenic, inflammatory, angiogenic, and metastasis-associated transcripts contain AREs within their 3′ untranslated regions, the balance between TTP-mediated decay and HuR-mediated stabilization critically influences tumor biology. Accumulating evidence demonstrates that loss of TTP expression or activity and cytoplasmic accumulation of HuR are recurrent features across multiple cancer types, including breast, colorectal, pancreatic, gastric, liver, ovarian, and lung cancers. Importantly, several studies indicate that the reciprocal interplay between these proteins establishes a post-transcriptional rheostat controlling cancer-associated RNA regulons. This review summarizes current knowledge regarding the molecular biology of TTP and HuR, emphasizing their opposing functions in mRNA metabolism and cancer progression. We discuss mechanisms regulating their expression, localization, phosphorylation, and RNA-binding activity; analyze cancer-specific evidence; and examine models in which both proteins are co-expressed or functionally interconnected. Finally, we evaluate therapeutic strategies aimed at restoring TTP function or inhibiting HuR activity and discuss future perspectives for targeting post-transcriptional regulatory networks in oncology.
BACKGROUND Nucleolar protein 2 (NOP2), an RNA methyltransferase that mediates m5C modification, has been implicated in cancer progression; however, its specific role in lung adenocarcinoma (LUAD) remains unclear. This study investigated the functional significance of NOP2 and its regulation of FK506-binding protein 4 (FKBP4) in LUAD pathogenesis. MATERIALS AND METHODS The human normal alveolar epithelial cell line HPAEpiC and the LUAD cell lines A549 and H1975 were utilized in this study. In vivo experiments were conducted using male Sprague-Dawley rats. The functional roles of NOP2 and FKBP4 were explored by transfecting LUAD cells with overexpression vectors or small interfering RNAs (siRNAs). Quantitative real-time PCR, western blotting, immunofluorescence, and immunohistochemical staining analyses were used to evaluate NOP2 and FKBP4 expression in cells and tissues. Cell viability and proliferation were assessed using Cell Counting Kit-8 assays and 5-ethynyl-2'-deoxyuridine (EdU) staining. Apoptosis was measured by flow cytometry and TUNEL staining. Transwell assays were conducted to determine cell migration and invasion. Co-immunoprecipitation and RNA pulldown assays were conducted to characterize the interaction between NOP2 and FKBP4. RESULTS Analysis of data from The Cancer Genome Atlas (TCGA) database revealed that elevated expression of NOP2 and FKBP4 correlated with poor prognosis in patients with LUAD. Both NOP2 and FKBP4 were significantly upregulated in LUAD cell lines compared to normal controls. Knockdown of NOP2 could inhibit LUAD cell proliferation, migration, and invasion, and enhance apoptosis. In vivo experiments confirmed that NOP2 depletion inhibited tumor growth and enhanced apoptosis. Mechanistically, NOP2 could directly bind to FKBP4 and regulate its expression. Importantly, FKBP4 knockdown reversed the oncogenic effects of NOP2 expression, establishing FKBP4 as a critical downstream effector of NOP2 in LUAD. CONCLUSION Our study demonstrates that NOP2 promotes LUAD progression by regulating FKBP4 expression, potentially through m5C methylation, thereby highlighting the NOP2/FKBP4 axis as a potential therapeutic target. Overall, these findings provide new insights into the epigenetic mechanisms driving LUAD aggressiveness.
Gastric cancer (GC) remains a leading cause of cancer-related deaths worldwide, with tumor stemness and metastasis driving poor prognosis. This study explores the role of eukaryotic translation initiation factor 4A1 (eIF4A1) in promoting these aggressive features in GC. eIF4A1 was found to be upregulated in stem-like (CD133+) GC cells. Gain- and loss-of-function experiments in cell lines, combined with xenograft, chemically induced, and organoid models, demonstrated that eIF4A1 enhanced cancer stemness, cell mobility, tumorigenesis, and metastasis. Mechanistically, eIF4A1 selectively promotes p70 ribosomal S6 kinase (p70S6K) mRNA translation, leading to increased glycogen synthase kinase 3 beta (GSK3β) phosphorylation, elevated nuclear β-catenin accumulation, and subsequent transcriptional activation of eIF4A1 via the β-catenin/transcription factor 7-like 2 (TCF7L2) complex, thus forming a positive feedback loop. Clinically, high expression of eIF4A1, p70S6K, and TCF7L2 correlates with unfavorable prognosis in GC patients. These findings highlight eIF4A1 as a key regulator of stemness and metastasis through a novel translational feedback mechanism, suggesting potential therapeutic targeting to disrupt tumor progression.
In this investigation, we examined the functional mechanism of the transcription factor zinc finger protein 695 (ZNF695) and its target gene chromobox protein homolog 8 (CBX8) in colorectal cancer (CRC) migration and invasion. HCT-116 and LOVO cell lines were used to establish cell models with knocked-down ZNF695 and knocked-down or over-expressed CBX8. To comprehensively evaluate the functional contributions of ZNF695 and CBX8 to cellular phenotypes, we employed CCK-8, wound-healing, and Transwell assays to evaluate cell proliferation, migration, and invasion, respectively. To assess the impact of ZNF695 on tumor progression, we generated a xenograft model utilizing nude mice. A FLAG-ZNF695 expression plasmid was constructed, and ChIP-seq experiments were performed. By integrating mRNA sequencing data following ZNF695 knockdown with highly expressed genes in CRC from the TCGA database, CBX8 was identified as a putative downstream target of ZNF695. We employed a dual-luciferase reporter assay to validate the specific binding affinity of ZNF695 toward the CBX8 promoter region. To elucidate the specific biological cascades modulated by ZNF695 and CBX8, we conducted a comprehensive pathway enrichment analysis. Rescue experiments were conducted to determine whether the ZNF695/CBX8 regulatory axis upregulates the expression of the Wnt signaling pathway downstream targets, AXIN2 and CCND1. Both in vitro assays and in vivo models confirmed that silencing ZNF695 dramatically suppresses CRC cell proliferation, migration, and invasion, while concurrently impeding tumor progression. ChIP-seq coupled with dual-luciferase reporter assays substantiated the direct binding of ZNF695 to the CBX8 promoter. Furthermore, CBX8 depletion significantly attenuated the migratory and invasive phenotypes of CRC cells. Restoring CBX8 expression effectively rescued the migratory and invasive deficits in CRC cells induced by ZNF695 silencing. Re-expression of CBX8 in ZNF695-silenced cells restored Wnt/β-catenin signaling activity, accompanied by increased expression of AXIN2 and CCND1. ZNF695 promotes CRC progression by transcriptionally activating CBX8 and subsequently enhancing Wnt/β-catenin signaling, thereby promoting tumor cell proliferation, migration, and invasion.
