Biology subjects

Hoch, N. C.

Publications and source records attributed to Hoch, N. C..

6 recordsLinked to original sources

bioRxiv2026

PARG activity is required for cell death by parthanatos

Cell death by a non-apoptotic pathway termed parthanatos is induced by hyperactivation of the DNA damage sensor PARP1, which uses NAD+ as a substrate to catalyse the poly-ADP-ribosylation (PARylation) of proteins. Parthanatos has been implicated in several pathological conditions such as ischaemia-reperfusion injury and neurodegenerative processes, including Alzheime[r]s and Parkinso[n]s diseases, as well as rare genetic disorders characterized by PARP1 hyperactivation. However, the precise sequence of molecular events by which excessive PARP1 activity causes cell death is currently unclear. Here we show that, in addition to PARP1-dependent PARylation, the execution of parthanatos also requires the hydrolysis of poly-ADP-ribose (PAR) chains by the glycohydrolase PARG. While complete inhibition of PARG activity prevents parthanatos, low levels of residual PARG activity are sufficient to support cell death by this pathway. Due to a phenotypic discrepancy between CRISPR/Cas9-generated PARG KO cells and PARG inhibitor-treated cells, we uncovered a new PARG splice variant predicted to encode an isoform of 53 kDa, termed PARG53, and provide evidence for the incorrect annotation of the previously reported isoforms PARG55 and PARG60. PARP1 hyperactivation during parthanatos leads to rapid and profound depletion of NAD+ and ATP pools, but full PARG inhibition only prevents the depletion of ATP, indicating that the depletion of these core metabolites can be uncoupled, and that ATP depletion is more closely correlated with cell death. This work sheds light on the initial steps of parthanatos induction, demonstrating that PAR formation and PAR hydrolysis are both required for this type of cell death.

biochemistry↗

bioRxiv2026

DUSP12 regulates NAT10-mediated RNA acetylation to modulate DNA repair and therapeutic response in hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the most common type of primary liver cancer arising from hepatocytes, is an aggressive hepatic malignancy with limited therapeutic options and poor prognosis. Chemotherapy remains an important treatment for advanced disease, though the mechanisms influencing drug sensitivity remain elusive. This study investigates the role of dual-specificity phosphatase 12 (DUSP12) and its interaction with the nucleolar protein NAT10 in the hepatic cellular response to genotoxic stress. We demonstrate that doxorubicin (DX) induces superior cytotoxicity over cisplatin in hepatocellular carcinoma models, associated with a stronger DNA damage response (DDR), nucleolar stress, and delocalization of NAT10 from the nucleolus to the nucleoplasm, where it colocalized with DUSP12. Genetic ablation of DUSP12 sensitized cells to DX, increasing DNA damage markers (p53, p-p53(Ser15), {gamma}H2AX(Ser139)) and delaying the repair of DNA strand breaks. DUSP12 knockout also caused redistribution of nucleolar proteins NAT10 and TCOF1. Pharmacological inhibition of NAT10 in DUSP12-deficient cells further enhanced DX sensitivity, revealing a synthetic-lethal interaction. We identified a direct association between NAT10 and DUSP12s functional domains, with evidence indicating NAT10 is a DUSP12 substrate. Consequently, DUSP12 knockout elevated NAT10 phosphotyrosine levels and reduced ac4C RNA acetylation, indicating functional impairment of NAT10. Corroborating these findings, patient data showed frequent DUSP12 amplification in HCC, correlating with poor survival and enrichment in DDR and ribosome biogenesis pathways. Our results establish the DUSP12-NAT10-ac4C axis as a molecular link between the DDR and nucleolar stress, highlighting previously unrecognized therapeutic vulnerability in HCC.

cancer biology↗

bioRxiv2025

LncRNA LINC00941 Links Oncogenic KRAS Signaling to Aggressiveness and Chemoresistance in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers, driven largely by oncogenic KRAS, yet effective targeted therapies remain unavailable. Long noncoding RNAs (lncRNAs) are emerging as key regulators of tumor biology, but their role in KRAS-driven PDAC is not well defined. To address this gap, we integrated RNA sequencing, exome, and clinical data from The Cancer Genome Atlas (TCGA) and identified 49 long intergenic noncoding RNAs (lincRNAs) differentially expressed according to KRAS status. Among the ten most abundant, LINC00941 and AC006262.5 showed the strongest differential expression in an independent PDAC cohort from the International Cancer Genome Consortium (ICGC). Experimental validation in KRAS-mutant PDAC cell lines and isogenic pancreatic epithelial models confirmed KRAS-dependent regulation of LINC00941, which was consistently upregulated in patient tumors and correlated with poor prognosis in both TCGA and ICGC datasets. Single-cell transcriptomic analysis further demonstrated that LINC00941 is enriched in malignant epithelial populations. Functional assays revealed that LINC00941 silencing impaired migration and invasion, reduced DNA repair capacity, and sensitized PDAC cells to gemcitabine, while having little effect on viability. Supporting these findings, co-expression and enrichment analyses linked LINC00941 to pathways regulating cell adhesion, motility, extracellular matrix organization, and DNA repair. Together, these findings demonstrate that oncogenic KRAS reshapes the lncRNA landscape in PDAC and identify LINC00941 as a KRAS-regulated oncogenic lncRNA that promotes aggressiveness and chemoresistance, highlighting its prognostic value and potential as a therapeutic target.

cancer biology↗

bioRxiv2025

Simultaneous detection and quantification of adenine nucleotides in mammalian cultured cells by HPLC

Adenine nucleotides, including ATP, ADP, ADP-ribose, AMP, NAD+ and NADH, play central roles in cellular homeostasis and involved in multiple metabolic and signaling pathways. Owing to their broad functional relevance in cell biology, the accurate quantification of these metabolites is essential for diverse research areas such as bioenergetics, cell signaling and cancer biology. Several analytical methods have been described for the measurement of adenine nucleotides, ranging from enzymatic assays to mass spectrometry-based approaches. In this study, we developed a reverse-phase high-performance liquid chromatography (RP-HPLC) method with UV-Vis detection that enables the simultaneous quantification of ATP, ADP, ADP-ribose, AMP, NAD+ and NADH. This method is simple, sensitive within the physiological concentration range of all analytes, and capable of detecting biologically relevant changes in ATP, AMP and NAD+ levels induced by pharmacological treatments. Therefore, it presents an accessible and reliable alternative for quantification of these nucleotides in biological samples.

biochemistry↗

bioRxiv2024

Temporal Analysis of Pituitary Transcriptional Dynamics in Mice Models of Hypopituitarism During Postnatal Development

Congenital hypopituitarism is characterized by deficient pituitary hormone production, affecting growth and development. The molecular mechanisms underlying pituitary development and dysfunction in hypopituitarism remain incompletely understood. We investigated the expression of key pituitary development markers in three mouse models of congenital hypopituitarism, with molecular alterations in the Prop1, Pou1f1, and GSU genes across critical postnatal developmental stages: neonatal (P0), early postnatal (P7), pubertal (4 weeks), and adult (8 weeks). We assessed mRNA and protein levels of the pituitary stem cell markers (SOX2), proliferation marker (Ki67) and pituitary hormones, correlating these with pituitary function and disease. Prop1 deficiency led to significant upregulation of Sox2 and Hesx1 during early postnatal development and in adulthood, diverging from the relatively stable expression patterns observed in Pou1f1 and GSU mutants. Despite some variations, overall Sox2 and Ki67 expression profiles were similar between Prop1 and Pou1f1 mutants. Prop1 mutants exhibited altered pituitary morphology, with increased SOX2-positive cells suggesting disrupted stem cell migration. During the pubertal period, a subset of hormone-producing cells in Prop1 mutants co-expressed SOX2, indicating differentiation without restoring normal pituitary function. Hormone analysis revealed transient gonadotropin production and secretion during sexual maturation in Prop1 mutants, without recovery of the hypogonadal phenotype. Our study elucidates the complex transcriptional dynamics of pituitary development markers in mouse models of congenital hypopituitarism, highlighting the pivotal role of Prop1 in regulating stem cell marker expression. The distinct transcriptional responses in Prop1 mutants during key developmental windows shed light on the mechanisms of pituitary dysgenesis and the persistent inability to fully recover pituitary function, despite transient hormonal changes during puberty. These insights contribute to a better understanding of pituitary development and dysfunction in congenital hypopituitarism.

developmental biology↗

bioRxiv2021

The SARS-CoV-2 Nsp3 macrodomain reverses PARP9/DTX3L-dependent ADP-ribosylation induced by interferon signalling

SARS-CoV-2 non-structural protein 3 (Nsp3) contains a macrodomain that is essential for virus replication and is thus an attractive target for drug development. This macrodomain is thought to counteract the host interferon (IFN) response, an important antiviral signalling cascade, via the removal of ADP-ribose modifications catalysed by host poly(ADP-ribose) polymerases (PARPs). Here, we show that activation of the IFN response induces ADP-ribosylation of host proteins and that ectopic expression of the SARS-CoV-2 Nsp3 macrodomain reverses this modification in human cells. We further demonstrate that this can be used to screen for cell-active macrodomain inhibitors without the requirement for BSL-3 facilities. This IFN-induced ADP-ribosylation is dependent on the PARP9/DTX3L heterodimer, but surprisingly the expression of Nsp3 macrodomain or PARP9/DTX3L deletion do not impair STAT1 phosphorylation or the induction of IFN-responsive genes. Our results suggest that PARP9/DTX3L-dependent ADP-ribosylation is a downstream effector of the host IFN response and that the cellular function of the SARS-CoV-2 Nsp3 macrodomain is to hydrolyse this end product of IFN signalling, and not to suppress the IFN response itself.

molecular biology↗