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PubMed2026

Genome-Wide Impact of Human DBR1 Depletion on RNA Processing Networks Reveal a Connection Between Pre-mRNA Splicing, mRNA Surveillance and Stress Granule Dynamics.

The RNA lariat debranching enzyme DBR1 is essential for intron turnover and RNA metabolism, yet its broader impact on transcriptome regulation remains incompletely defined. To elucidate the consequences of DBR1 depletion, we performed transcriptome-wide RNA sequencing of DBR1-knockdown and wild-type HEK293 cells. Differential expression analysis revealed widespread perturbations in pathways linked to RNA splicing, mRNA surveillance, translational control, and stress-granule biology. Many of the most significantly altered transcripts encode splicing factors and RNA quality-control components, underscoring DBR1's influence on post-transcriptional regulation. Alternative splicing analysis showed changes across multiple event types, with exon skipping accounting for >50% of events, followed by mutually exclusive exons, alternative 5' and 3' splice sites, and retained introns, indicating that DBR1 depletion induces pervasive splicing defects. Direct spliceosome inhibition using isoginkgetin (blocks tri-snRNP recruitment) and pladienolide B (targets SF3B1) reproduced the DBR1-KD mis-splicing patterns of cell signaling genes and factors involved in RNA metabolism, supporting a functional link between DBR1 activity and alternative splicing. Notably, DBR1 knockdown revealed a subset of transcripts that are both NMD-sensitive and enriched within stress granules. Consistent with this observation, G3BP1 immunopurification and confocal microscopy further support a role for DBR1 and UPF1 in stress-granule dynamics, suggesting that these factors may participate at distinct stages to influence mRNA fate under stress conditions. Together, these findings indicate that DBR1 functions beyond lariat RNA turnover as a common regulator of RNA processing, transcriptome stability, and stress granule homeostasis, revealing intricate crosstalk between RNA splicing and RNA quality control pathways in human cells.

Humans↗

PubMed2026

Estrogen Receptor, GATA-3, TTF-1, and KRAS in Endometrial Carcinoma of No Specific Molecular Profile: Prognostic or Diagnostic Markers?

Endometrial carcinoma with no specific molecular profile (NSMP) is a clinicopathologically heterogeneous group of diseases with an overall intermediate prognosis. Prognostic refinement is needed for better personalized treatment. The updated European Society of Gynecological Oncology-European Society for Radiotherapy and Oncology-European Society of Pathology guidelines for endometrial carcinoma stratify NSMP according to histotype and estrogen receptor (ER) status. ER (with other ancillary markers) also helps differentiate histotypes of endometrial carcinoma. This study describes clinicopathological characteristics of ER-positive and -negative-NSMP endometrial carcinoma. Furthermore, we investigate the prognostic and diagnostic significance of ER, GATA3, TTF1, and KRAS in a large and relatively unselected NSMP carcinoma cohort. POLE sequencing results and immunohistochemistry for p53, mismatch repair proteins, and ER were available for 930 samples of endometrial carcinoma. Within NSMP cases (n = 377), 22 samples presented ER staining in <1% of the carcinoma cells, 5 cases in 1% to 9%, and 350 cases in ≥10%. ER expression ≥10% predicted an excellent outcome (comparable with POLE-mutated cases) in univariable analysis, where ER negativity (<10%) was associated with a poor outcome (comparable with p53 abnormal cases). Most ER-positive NSMP cases were low-grade endometrioid carcinomas, whereas most ER-negative NSMP cases were nonendometrioid or high-grade endometrioid carcinomas. In addition to high-risk histotype, ER negativity was associated with various other clinicopathological risk factors. In multivariable analysis adjusting for histotype and other risk factors, ER did not independently predict disease progression (P = .814). No disease-related deaths were observed in the rare (n = 3) patients with ER-negative-low-grade endometrioid carcinoma. GATA3/TTF1 positivity and KRAS mutation were discovered not only in mesonephric-like carcinoma but also in endometrioid carcinoma. No prognostic relevance was found for these markers. In conclusion, the different prognosis of ER-positive vs ER-negative-NSMP endometrial carcinoma is not attributable to ER status itself but rather to its strong correlation with histotype and other clinicopathological risk factors. Limited specificity of GATA3, TTF1, and KRAS warrants caution in their use as diagnostic markers of mesonephric-like carcinoma.

Humans↗

PubMed2026

CRISPR/Cas9-mediated editing of ERCC6 in iPSCs: A disease model for Cockayne Syndrome type B.

Cockayne Syndrome type B (CSB) is caused by mutations in the ERCC6 gene, which encodes a key protein involved in transcription-coupled nucleotide excision repair (TC-NER) and chromatin remodeling. Deficiency in CSB leads to defective transcriptional recovery after DNA damage, oxidative stress accumulation, and progressive neurodegeneration. In this work, we generated a CRISPR/Cas9-engineered human induced pluripotent stem cell (iPSC) line, IUFi004-A-12, carrying a homozygous mutation in ERCC6 causing a premature stop codon in its 10th exon. The modified iPSCs displayed normal morphology, expressed pluripotency markers, and differentiated into all three germ layers. This model enables mechanistic studies of CSB dysfunction and facilitates therapeutic development for Cockayne Syndrome.

Humans↗

PubMed2024

The ARK2N-CK2 complex initiates transcription-coupled repair through enhancing the interaction of CSB with lesion-stalled RNAPII.

Transcription is extremely important for cellular processes but can be hindered by RNA polymerase II (RNAPII) pausing and stalling. Cockayne syndrome protein B (CSB) promotes the progression of paused RNAPII or initiates transcription-coupled nucleotide excision repair (TC-NER) to remove stalled RNAPII. However, the specific mechanism by which CSB initiates TC-NER upon damage remains unclear. In this study, we identified the indispensable role of the ARK2N-CK2 complex in the CSB-mediated initiation of TC-NER. The ARK2N-CK2 complex is recruited to damage sites through CSB and then phosphorylates CSB. Phosphorylation of CSB enhances its binding to stalled RNAPII, prolonging the association of CSB with chromatin and promoting CSA-mediated ubiquitination of stalled RNAPII. Consistent with this finding, Ark2n-/- mice exhibit a phenotype resembling Cockayne syndrome. These findings shed light on the pivotal role of the ARK2N-CK2 complex in governing the fate of RNAPII through CSB, bridging a critical gap necessary for initiating TC-NER.

DNA Repair Enzymes↗

PubMed2025

Comparative Analysis of Somatic and Germline Polymerase Proofreading Deficiencies in Cancer: Molecular and Clinical Implications.

Polymerases ε and δ maintain genome integrity through exonuclease proofreading. Germline and somatic pathogenic variants (PVs) in the exonuclease domain (ED) of POLE and POLD1 impair proofreading, causing hypermutated tumors. Despite shared mutational features that make these tumors highly immunogenic, molecular and clinical distinctions between POLE and POLD1 mutations and between somatic and germline variants remain incompletely understood. We compared the molecular and clinical characteristics of POLE and POLD1 ED PVs (n = 31), assessing their location, pathogenicity, clinical phenotypes, mismatch repair (MMR) status, tumor mutational burden, and signatures. We analyzed 360 proofreading-deficient tumors (source: The Cancer Genome Atlas [TCGA] and Catalogue Of Somatic Mutations In Cancer [COSMIC]) and 70 families (249 individuals) with polymerase proofreading-associated polyposis. All germline and somatic PVs had high AlphaMissense scores (0.87-1) and clustered within or near Exo motifs. Recurrent, nonfounder germline PVs, POLE L424V and POLD1 S478N, showed low/modest REVEL scores. Somatic variants occurred mainly in endometrial cancers (75% of proofreading-deficient TCGA cancers), whereas colorectal cancer predominated in polymerase proofreading-associated polyposis (56% of carriers). Cancer risks and tumor spectra differed between POLE and POLD1 PV carriers. Aggressive hereditary phenotypes were linked to either specific POLE PVs (eg, S297F, V411L, P436R, M444K, A456P, and S461T) or the co-occurrence of germline ED PVs with germline MMR gene PVs. Distinct hypermutator profiles were confirmed for polymerase ε and polymerase δ proofreading deficiencies via unique mutational signatures (Polymerase ε: SBS10a/b, SBS28; Polymerase δ: SBS10c/d). Tumors with combined proofreading and MMR deficiencies had significantly higher tumor mutational burden and a shift in the associated mutational spectra. Unlike POLE, POLD1 ED PVs exhibited haplosufficiency, typically requiring a somatic second hit (eg, loss of heterozygosity) or MMR deficiency to drive hypermutation. In conclusion, differences between POLE and POLD1 and between somatic and germline mutations influence clinical presentation, mutagenic potential, and reliance on cooperating defects in tumorigenesis. These insights advance the understanding of proofreading-deficient cancers, with implications for diagnostics, genetic counseling, and precision oncology.

Humans↗

PubMed2025

Cockayne syndrome mice reflect human kidney disease and are defective in de novo NAD biosynthesis.

Cockayne Syndrome (CS) is a premature aging disorder caused by mutations in the CSA and CSB genes involved in DNA metabolism and other cellular processes. CS patients display many features including premature aging, neurodegeneration, and kidney abnormalities. Nicotinamide dinucleotide (NAD+) deprivation has been observed in CS patient-derived cells. NAD+ has essential roles in regulating cellular health, stress responses, and renal homeostasis. While kidney dysfunction is a common feature in CS patients, its molecular pathogenesis is not understood. Here, we report that severe kidney pathology is present in CS A and B mice. We find that the NAD+ biosynthetic pathways are impaired in kidneys from these mice. Using human renal tubular epithelial cells, we show that CSA/B downregulation causes persistent activation of the ATF3 transcription factor on the quinolinate phosphoribosyl transferase gene locus, a rate-limiting enzyme in de novo NAD+ biosynthesis in the kidney, causing impaired transcription and deficient NAD+ homeostasis.

Animals↗

PubMed2025

Molecular features influencing clinical outcome of advanced HER2-positive gastric cancer receiving trastuzumab plus chemotherapy.

BACKGROUND: Less than half of the human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC) patients respond to trastuzumab plus chemotherapy, and the outcomes are unsatisfactory. Understanding the underlying mechanisms remains crucial for identifying patients who are more likely to benefit from treatment. PATIENTS AND METHODS: We performed targeted DNA sequencing on paired pre-treatment and progressive tumour tissues from 22 HER2-positive advanced GC patients undergoing first-line treatment with trastuzumab and chemotherapy. Clinicopathological and genomic characteristics were assessed for the correlation with clinical outcomes. RESULTS: A performance status (PS) of 0-1 was associated with improved progression-free survival (PFS) and overall survival (OS) than a PS of 2. Poorly differentiated tumours exhibited shorter PFS than moderate or moderate-poor ones. Pre-treatment amplification of MYC or TOP2A gene was association with increased PFS, and suggested a potential benefit for OS. Patients with higher tumour mutation burden (TMB) experienced significantly worse PFS, while higher chromosome instability (CIN) appeared to be correlated with longer PFS. Compared to non-responders, responders had a higher CIN but similar TMB and intratumoural heterogeneity (ITH). PS and MYC amplification emerged as independent factors related to PFS according to multivariate survival analysis. Additionally, after treatment, TMB significantly increased in non-responders, while CIN significantly decreased in responders. CONCLUSIONS: Pre-treatment MYC amplification and PS were independently associated with clinical outcomes in HER2-positive advanced GC patients treated with first-line trastuzumab plus chemotherapy. Dynamic post-treatment changes in TMB and CIS provide valuable insights into the relationship between therapeutic response and distinct evolutionary trajectories.

Humans↗

PubMed2026

Deficiency in POLE Exonuclease Causes Synthetic Lethality in Highly Aneuploid Cancer Cells.

UNLABELLED: Aneuploidy is a hallmark of cancer and is associated with drug resistance and poor clinical outcomes across diverse cancer types. However, no therapies have been clinically established to target highly aneuploid tumors. By analyzing nearly half a million tumor samples subjected to comprehensive genomic profiling, we identified a striking mutual exclusivity between POLE exonuclease domain mutations and high aneuploidy burden. This observation was independently validated using data from The Cancer Genome Atlas (TCGA) and the Cancer Cell Line Encyclopedia (CCLE). Probabilistic modeling revealed that the elevated quantity and unique spectrum of mutations induced by POLE exonuclease deficiency increase the likelihood of inactivating essential genes on chromosome arms harboring losses, leading to a synthetic lethal phenotype in highly aneuploid cells. Functional experiments demonstrated that POLE exonuclease activity is essential for the viability of highly aneuploid cancer cell lines but dispensable in diploid cells. These findings suggest that selective inhibition of POLE exonuclease activity may represent a promising therapeutic strategy for targeting highly aneuploid tumors. SIGNIFICANCE: An integrated approach using large-scale genomic analyses, probabilistic modeling and functional validation identified POLE exonuclease as a potential synthetic lethal target to overcome cancer aneuploidy.

Humans↗

PubMed2026

The clinical landscape of POLE-mutant colorectal cancer: a retrospective analysis of real-world outcome.

BACKGROUND: Pathogenic mutations in the POLE gene disrupt its proofreading function during DNA replication, causing an accumulation of erroneous nucleotide incorporations. This defect leads to a significantly elevated tumor mutation burden (TMB) and increased generation of tumor neoantigens. These molecular characteristics suggest a potential association between POLE-mutant tumors and distinct prognostic outcomes in colorectal cancer (CRC); however, clinical evidence supporting this correlation remains limited. METHODS: We retrospectively collected a cohort of CRC patients harboring pathogenic POLE mutations. Comparative analyses were performed between POLE-mutant and POLE wild-type CRCs regarding their clinical characteristics, prognostic outcomes, and genomic profiles. Additionally, we evaluated the response to immunotherapy in metastatic POLE-mutant CRC cases. RESULTS: Among 35,108 CRC patients, pathogenic POLE mutations were identified in 261 individuals, accounting for 0.74% of the cohort. The median age at diagnosis for POLE-mutant patients was 48 years, with a male predominance (74.4%) and a substantial proportion (50.4%) of tumors localized in the right-sided colon. All patients with pathogenic POLE mutations exhibited hypermutated phenotypes, characterized by a median TMB of 235.26 mutations per megabase (range: 71.20-719.00 mutations/Mb). In stage II CRC, POLE mutations were significantly associated with a reduced risk of recurrence (hazard ratio [HR] 0.344, 95% confidence interval [CI] 0.157-0.754, p = 0.008) when compared to POLE wild-type, microsatellite stable CRC patients. However, this association was not evident in stage III patients (HR 1.004, 95% CI 0.490-2.057, p = 0.992). Importantly, the incorporation of immune checkpoint inhibitors in first-line treatment regimens significantly improved progression-free survival (HR = 0.247, 95% CI 0.117-0.552, p = 0.0002) and overall survival (HR = 0.317, 95% CI 0.103-1.143, p = 0.0832) in metastatic CRC patients with pathogenic POLE mutations. CONCLUSIONS: Pathogenic POLE-mutant CRC constitutes a relatively rare, yet clinically important, subtype. These cancers exhibit distinct clinicopathological and genomic features. Our results indicate that mutations in the POLE gene may serve as a valuable prognostic marker and a potential indicator of benefit to immunotherapy in CRC, offering promising avenues for personalized treatment strategies.

Humans↗

PubMed2026

Analysis of gene expression changes upon topobexin treatment and TOP2B-knockout in hiPSC-derived cardiomyocytes.

The role of DNA topoisomerase II beta (TOP2B) in cardiomyocyte differentiation is poorly understood. To address this, human induced pluripotent stem cells (hiPSC) were differentiated into cardiomyocytes (CM) that were wild type (WT) or contained a genomic deletion of Topoisomerase 2B (BKO). Both WT and BKO hiPSC could be induced to differentiate into sheets of beating cardiomyocytes. BKO hiPSC take slightly longer to differentiate into sheets of beating CM than WT iPSC. RNA was prepared from both undifferentiated and differentiated WT and BKO hiPSC. RNA-seq was used to examine gene expression changes when the WT and BKO hiPSC were differentiated into CM. Gene expression changes following differentiation of BKO cells were largely similar to those in WT cells. In addition, the differentiated WT CM were treated with dexrazoxane (ICRF-187), a TOP2 catalytic inhibitor that targets both TOP2A and TOP2B, or topobexin, a new TOP2B selective catalytic inhibitor. Topobexin inhibition partially phenocopied a TOP2B deletion and thereby providing an alternative to TOP2B gene knockout in many cell lines. In future, hiPSC derived CM with and without TOP2B and inhibition by topobexin ex vivo CM could be used to study anthracycline-induced cardiotoxicity and to screen for cardioprotectants.

Myocytes, Cardiac↗