Biology subjects

Dekker, F. J.

Publications and source records attributed to Dekker, F. J..

5 recordsLinked to original sources

bioRxiv2026

Fasting disrupts the InsP6 HDAC3 axis to drive ER stress-mediated clearance of DNA-damaged cells and enforce tissue quality control.

Fasting drives metabolic adaptation but also elicits acute cellular stress. How this stress shapes tissue integrity is unknown. Here, we show that in the intestine, fasting depletes growth factor signaling, which triggers cellular stress. This response functions as a tissue quality-control checkpoint that selectively eliminates pre-existing DNA-damaged cells while sparing healthy counterparts. A short-term fast diminishes TGF-{beta} signaling and elicits endoplasmic reticulum (ER) stress, driving DNA-damaged intestinal cells beyond an apoptotic threshold, thereby reducing the inflammatory burden. Mechanistically, loss of TGF-{beta} signaling triggers FBXO22-Cullin1-mediated degradation of the inositol kinase IPMK, leading to depletion of inositol hexaphosphate (InsP). InsP loss attenuates HDAC3 activity and initiates coordinated epigenetic and post-translational reprogramming, thereby increasing CDK5RAP3 abundance. Elevated CDK5RAP3 inhibits ribosomal RPL26 UFMylation, thereby amplifying ER stress and selectively licensing apoptosis in DNA-damaged cells. Collectively, fasting disrupts a TGF-{beta}-InsP6-HDAC3 axis to drive ER stress-dependent clearance of DNA-damaged cells, enforcing tissue quality control.

cell biology↗

bioRxiv2024

Blocking MIF secretion enhances CAR T-cell efficacy against neuroblastoma

While chimeric antigen receptor (CAR) T-cell therapies are showing highly promising first results in neuroblastoma, immunosuppressive tumor microenvironments (TME) limit T cell persistence and durable clinical efficacy. To improve CAR T-cell efficacy further, we applied a multi-omics approach including single-cell RNA sequencing and proteomics, which identified 13 targetable immunosuppressive factors in neuroblastoma. Of these, macrophage migration inhibitory factor (MIF) and midkine (MDK) were validated across multiple published RNA datasets. Moreover, they were secreted in high abundance by neuroblastoma tumoroids. Functional validation experiments revealed MIF as a potent inhibitor of CAR T-cells, in vitro and in vivo. Degradation of MIF by PROTAC technology significantly enhanced CAR T-cell activation targeting GPC2 and B7-H3, providing a potential intervention against MIF. By defining the immunosuppressive effects of neuroblastomas TME on CAR T-cell efficacy, particularly the pivotal role of MIF, we provide a therapeutic strategy for improving adoptive cell therapies for this pediatric malignancy.

cancer biology↗

bioRxiv2023

A dynamic bias in chromatin protein deposition at G-quadruplex sites

Previous studies indicate that genomic loci harboring G-quadruplexes (G4s)--stacked structures that can form in single-stranded DNA--can be linked to epigenetic instability. However, the role of chromatin redistribution and the genome-wide nature of this process need further investigation. Here, we provide experimental evidence that connects G4s to alterations in the deposition of chromatin proteins. We have used metabolic labelling and immunoprecipitation of new and parental proteins in hRPE-1 cells to investigate global chromatin deposition dynamics. We identify a reciprocal, local bias in chromatin protein deposition at G4 sites favoring the association of parental proteins with the G4 and new proteins with the C4 DNA strand. The deposition bias at G4 sites does not depend on replication directionality and is strengthened by G4 stabilization. Slowing down replication forks upon hydroxyurea treatment reverses the bias, supposedly affected by decoupling between helicase and polymerase. Interestingly, upon combined G4 stabilization and slowing of the replication forks, new proteins exhibit a redistribution pattern similar to G4 stabilization alone, while parental protein redistribution more resembles one after hydroxyurea treatment, hinting at mechanistic differences between parental and new histone distribution. We also report that the genomic distribution of putative quadruplexes is not random and depends on loop size, where G4s with shorter loops have a preference for the DNA strand replicated by leading and G4s with longer loops by lagging strand replication. These findings provide insight into the mechanisms behind G4 occurrence and its role in epigenetic instability and help to improve our understanding of the factors influencing biases in global chromatin protein redeposition.

molecular biology↗

bioRxiv2021

Inversion of asymmetric histone deposition upon replication stress

Following DNA replication, equal amounts of histones are distributed over sister chromatids by re-deposition of parental histones and deposition of newly synthesized histones. Molecular mechanisms balancing the allocation of new and old histones remain largely unknown. Here, we studied the genome-wide distribution of new histones relative to parental DNA template strands and replication initiation zones using double-click-seq. In control conditions, new histones were preferentially found on DNA replicated by the lagging strand machinery. Strikingly, replication stress induced by hydroxyurea or curaxin treatment, and inhibition of ATR or p53 inactivation, inverted the observed histone deposition bias to the strand replicated by the leading strand polymerase in line with previously reported effects on RPA occupancy. We propose that asymmetric deposition of newly synthesized histones onto sister chromatids reflects differences in the processivity of leading and lagging strand synthesis.

cell biology↗

bioRxiv2019

Pharmacological inhibition of lysine-specific demethylase 1 (LSD1) induces global transcriptional deregulation and ultrastructural alterations that impair viability in Schistosoma mansoni

Treatment and control of schistosomiasis still rely on only one effective drug, praziquantel (PZQ), and due to mass treatment, the increasing risk of selecting for schistosome strains that are resistant to PZQ has alerted investigators to the urgent need to develop novel therapeutic strategies. The histone-modifying enzymes (HMEs) represent promising targets for the development of epigenetic drugs against Schistosoma mansoni. In the present study, we targeted the S. mansoni lysine-specific demethylase 1 (SmLSD1), a transcriptional corepressor, using a novel and selective synthetic inhibitor, MC3935. We synthesized a novel and potent LSD1 inhibitor, MC3935, which was used to treat schistosomula or adult worms in vitro. By using cell viability assays and optical and electron microscopy, we showed that treatment with MC3935 affected parasite motility, egg-laying, tegument, and cellular organelle structures, culminating in the death of schistosomula and adult worms. In silico molecular modeling and docking analysis suggested that MC3935 binds to the catalytic pocket of SmLSD1. Western blot analysis revealed that MC3935 inhibited SmLSD1 demethylation activity of H3K4me1/2. Knockdown of SmLSD1 by RNAi recapitulated MC3935 phenotypes in adult worms. RNA-seq analysis of MC3935-treated parasites revealed significant differences in gene expression related to critical biological processes. Collectively, our findings show that SmLSD1 is a promising drug target for the treatment of schistosomiasis and strongly support the further development and in vivo testing of selective schistosome LSD1 inhibitors. Author SummarySchistosomiasis mansoni is a chronic and debilitating tropical disease caused by the helminth Schistosoma mansoni. The control and treatment of the disease rely almost exclusively on praziquantel (PZQ). Thus, there is an urgent need to search for promising protein targets to develop new drugs. Drugs that inhibit enzymes that modify the chromatin structure have been developed for a number of diseases. We and others have shown that S. mansoni epigenetic enzymes are also potential therapeutic targets. Here we evaluated the potential of the S. mansoni histone demethylase LSD1 (SmLSD1) as a drug target. We reported the synthesis of a novel and potent LSD1 inhibitor, MC3935, and show that it selectively inhibited the enzymatic activity of SmLSD1. Treatment of juvenile or adult worms with MC3935 caused severe damage to the tegument of the parasites and compromised egg production. Importantly, MC3935 proved to be highly toxic to S. mansoni, culminating in the death of juvenile or adult worms within 96 h. Transcriptomic analysis of MC3935-treated parasites revealed changes in the gene expression of hundreds of genes involved in key biological processes. Importantly, SmLSD1 contains unique sequences within its polypeptide chain that could be explored to develop a S. mansoni selective drug.

molecular biology↗