Biology subjects

Paeschke, K.

Publications and source records attributed to Paeschke, K..

6 recordsLinked to original sources

bioRxiv2026

G-quadruplex targeting by CX-5461 as a novel therapeutic strategy in testicular germ cell tumors

Testicular germ cell tumors (TGCTs) are highly curable malignancies; however, resistance to cisplatin-based therapy remains a critical clinical challenge. G-quadruplexes (G4s) are specific guanine rich, four-stranded DNA structures that are enriched at distinct genomic regions. Due to their stability, G4s can influence genome stability, gene expression, DNA replication as well as telomere maintenance. G4 stabilization by small molecules has been shown to have anticancer effects in several tumors but remains underexplored in TGCTs. Here, we systematically evaluated the effect of six different G4- ligands (CX-5461, CX-3543, BRACO19, PDS, CM03 and RHPS4) on TGCT cell lines and non-malignant fibroblasts. Among those G4 ligands, CX-5461 showed strongest cellular changes in TGCTs. We observed dose- and time-dependent G4 stabilization upon CX-5461 treatment in TGCT cells, accompanied by impaired RNA polymerase I-dependent transcription and induction of DNA double-strand breaks, whereas only minimal effects were observed in control fibroblasts. These effects led to the activation of p53 signaling, and consequently an upregulation of canonical p53 target genes, including CDKN1A, MDM2, PIDD1, GADD45A, ZMAT3, SESN1 and PPM1D, resulting in G2/M cell-cycle arrest and apoptosis. The presence of potential quadruplex forming sequences (PQSs) in the promoters or gene bodies of these genes suggests that G4 structures may contribute to the p53 transcriptional response. Collectively, these data demonstrate that CX-5461 appears as highly potent G4-ligand inducing p53-dependent molecular cascades leading to cell death in germ cell tumors. Unlike in many other tumors, p53 remains functionally intact in TGCTs, suggesting that CX-5461-mediated activation of the p53 pathway could be selectively targeted as a therapeutic strategy in TGCTs.

cancer biology↗

bioRxiv2024

Telomeric lncRNA TERRA localizes to stress granules in human ALT cells

TERRA, the lncRNA derived from the ends of chromosomes, has a number of well-described nuclear roles including telomere maintenance and homeostasis. A growing body of evidence now points at its role in human cells outside of nucleus--it has been found to be a component of extracellular vesicles, a player in inflammation signalling and its capacity for translation has been shown. In this work, using a combination of sensitive microscopy methods, cellular fractionation, proteomics and transcriptome analysis, we demonstrate directly for the first time that TERRA is present in the cytoplasm of human telomerase-negative cells, especially upon various stress stimuli, and that it associates with stress granules. Confirming the presence of TERRA in the cytoplasm, our work fills an important gap in the field, and contributes to the discussion about the role of TERRA as a transcript involved in nucleo-cytoplasmic stress communication.

molecular biology↗

bioRxiv2023

Drosophila macrophages control systemic cytokine levels in response to oxidative stress via a non-canonical DNA damage repair signaling cascade

Environmental factors, infection, or injury can cause oxidative stress in diverse tissues and loss of tissue homeostasis. Effective stress response cascades, conserved from invertebrates to mammals, ensure reestablishment of homeostasis and tissue repair. Hemocytes, the Drosophila blood-like cells, rapidly respond to oxidative stress by immune activation. However, the precise signals how they sense oxidative stress and integrate these signals to modulate and balance the response to oxidative stress in the adult fly are ill-defined. Furthermore, hemocyte diversification was not explored yet on oxidative stress. Here, we employed high throughput single nuclei RNA-sequencing to explore hemocytes and other cell types, such as fat body, during oxidative stress in the adult fly. We identified distinct cellular responder states in plasmatocytes, the Drosophila macrophages, associated with immune response and metabolic activation upon oxidative stress. We further define oxidative stress-induced DNA damage signaling as a key sensor and a rate-limiting step in immune-activated plasmatocytes controlling JNK-mediated release of the pro-inflammatory cytokine unpaired-3. We subsequently tested the role of this specific immune activated cell stage during oxidative stress and found that inhibition of DNA damage signaling in plasmatocytes, as well as JNK or upd3 overactivation, result in a higher susceptibility to oxidative stress. Our findings uncover that a balanced composition and response of hemocyte subclusters is essential for the survival of adult Drosophila on oxidative stress by regulating systemic cytokine levels and cross-talk to other organs, such as the fat body, to control energy mobilization.

immunology↗

bioRxiv2022

A conserved isoleucine in the binding pocket of RIG-I controls immune tolerance to mitochondrial RNA

RIG-I is a cytosolic receptor of viral RNA essential for the immune response to numerous RNA viruses. Accordingly, RIG-I must sensitively detect viral RNA yet tolerate abundant self-RNA species. The basic binding cleft and an aromatic amino acid of the RIG-I C-terminal domain(CTD) mediate high-affinity recognition of 5triphosphorylated and 5base-paired RNA(dsRNA). Here, we found that, while 5unmodified hydroxyl(OH)-dsRNA demonstrated residual activation potential, 5-monophosphate(5p)-termini, present on most cellular RNAs, prevented RIG-I activation. Determination of CTD/dsRNA co-crystal structures and mutant activation studies revealed that the evolutionarily conserved I875 within the CTD sterically inhibits 5p-dsRNA binding. RIG-I(I875A) was activated by both synthetic 5p-dsRNA and endogenous long dsRNA within the polyA-rich fraction of total cellular RNA. RIG-I(I875A) specifically interacted with a long, highly structured, polyA-bearing, non-coding mitochondrial(mt) RNA, and depletion of mtRNA from total RNA abolished its activation. Altogether, our study demonstrates that avoidance of 5p-RNA recognition is crucial to preventing mtRNA-triggered RIG-I-mediated autoinflammation.

immunology↗

bioRxiv2022

cGAS/STING-DEPENDENT SENSING OF ENDOGENOUS RNA

Defects in nucleic acid metabolizing enzymes lead to spontaneous but selective activation of either cGAS/STING or RIG-like receptor (RLR) signaling, causing a pathogenic type I interferon response and inflammatory diseases. In these pathophysiological conditions, cGAS-driven IFN production is linked to spontaneous DNA damage. Physiological, or tonic, IFN signaling on the other hand is essential to functionally prime nucleic acid sensing pathways. Here we show that low-level chronic DNA damage in mice lacking the Aicardi-Goutieres syndrome gene SAMHD1 reduced tumor-free survival when crossed to a p53-deficient, but not to DNA mismatch repair-deficient background. Increased DNA damage did not result in higher levels of type I interferon. Instead, we found that the chronic interferon response in SAMHD1-deficient mice was driven by the MDA5/MAVS pathway but required functional priming through the cGAS/STING pathway. Our work positions cGAS/STING upstream of tonic IFN signaling and highlights an important role of the pathway in physiological and pathophysiological innate immune priming. SummaryLoss of the dNTPase and DNA repair enzyme SAMHD1 is associated with cancer and causes systemic autoimmunity. We show transformation-promoting spontaneous DNA damage and MDA5-driven but cGAS/STING-dependent chronic type I interferon production in SAMHD1-deficient mice.

immunology↗

bioRxiv2017

DHX36 binding at G-rich sites in mRNA untranslated regions promotes translation

Translation efficiency can be affected by mRNA stability and secondary structures, including so-called G-quadruplex (G4) structures. The highly conserved and essential DEAH-box helicase DHX36/RHAU is able to resolve G4 structures on DNA and RNA in vitro, however a system-wide analysis of DHX36 targets and function is lacking. We globally mapped DHX36 occupancy in human cell lines and found that it preferentially binds to G-rich sequences in the coding sequences (CDS) and 5' and 3' untranslated regions (UTR) of more than 4,500 mRNAs. Functional analyses, including RNA sequencing, ribosome footprinting, and quantitative mass spectrometry revealed that DHX36 decreased target mRNA stability. However, target mRNA accumulation in DHX36 KO cells did not lead to a significant increase in ribosome footprints or protein output indicating that they were translationally incompetent. We hypothesize that DHX36 resolves G4 and other structures that interfere with efficient translation initiation.

bioinformatics↗