Search Results (83)

Poly(ADP-ribose) polymerases (PARPs) regulate genome maintenance through NAD⁺-dependent ADP-ribosylation, yet PARP function in fungi remains poorly defined. Here, we reconstituted the activity of the Magnaporthe oryzae PARP1 homolog (MoPARP1) in Saccharomyces cerevisiae, a genetically tractable organism that lacks endogenous PARP enzymes. Upon galactose induction, expression of MoPARP1 reduced yeast growth, whereas a catalytically inactive mutant showed no defect, indicating that the growth phenotype depends on PARP catalytic activity. Consistent with this requirement, PARylation was detected in MoPARP1-expressing yeast cells but not in the catalytic mutant. In a multidrug transporter-deficient background, the PARP inhibitor 3-aminobenzamide and the clinically used PARP inhibitor olaparib rescued the growth of MoPARP1-expressing strains, establishing a framework for inhibitor testing in vivo. Finally, MoPARP1-GFP localized to the nucleus independent of catalytic activity, supporting correct targeting in this heterologous system. Together, these findings establish yeast as a platform to dissect fungal PARP biology and evaluate chemical inhibition. Full article

Tankyrases (TNKS1 and TNKS2) are multifunctional enzymes of the poly(ADP-ribose) polymerase (PARP) family that regulate cellular homeostasis by catalyzing poly(ADP-ribosyl)ation and stabilizing protein–protein interactions through their ankyrin repeat clusters. By engaging with diverse sets of proteins, TNKSs act as central hubs that coordinate signaling and metabolic pathways. In this review, we discuss how TNKS –protein interactions underpin their roles across multiple biological pathways, including Wnt/β-catenin, YAP and SRC signaling, mTORC1 signaling, DNA damage repair (via PARP crosstalk and recruitment of repair factors), telomere maintenance, cell-cycle regulation, glucose metabolism, cytoskeleton rearrangement, autophagy, proteasomal degradation, and apoptosis. We highlight the structural basis of these interactions, emphasizing ankyrin repeat domain recognition motifs and the consequences of TNKS-mediated PARylation on protein stability and localization. By integrating findings from oncology, virology, and metabolism, we illustrate how TNKS functions as a nodal regulator linking genome stability, signaling fidelity, and metabolic control. The interplay between TNKS and these varied pathways is essential for the well-being of the organism, with its dysregulation having severe biological and clinical consequences, which are discussed here. Finally, we consider therapeutic implications of disrupting TNKS–protein interactions, with particular attention paid to selective small-molecule inhibitors and their translational potential in cancer, viral infections, and degenerative diseases. Full article

Exercise adaptation depends on a dynamic alternation between catabolic and anabolic states coordinated primarily by AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR). While transient activation of these pathways underpins beneficial molecular remodeling, the system-level consequences of sustained anabolic drive remain insufficiently conceptualized in exercise biology. This article presents a conceptual mechanistic narrative review integrating evidence from molecular nutrition, exercise physiology, redox biology, and epigenetic regulation to define limits of adaptive signaling. We propose the Metabolic Overdrive Model, a systems-level framework describing the transition from adaptive AMPK–mTOR oscillation to a high-anabolic lock-in state characterized by persistent mTORC1 activation, suppressed AMPK signaling, altered NAD⁺ economy (SIRT1–PARP imbalance), redox dysregulation, and progressive epigenetic drift. Using exercise and training as models of sustained metabolic stress, we synthesize mechanistic parallels across energy sensing, oxidative signaling, and chromatin regulation without implying pathological causality. The framework generates testable predictions linking prolonged post-exercise anabolic signaling (>24 h) to specific molecular signatures, including AMPK phosphorylation status, NAD⁺ availability, PARylation, histone acetylation, and DNA methylation dynamics. By reframing exercise adaptation as a loss-of-oscillation phenomenon rather than a linear continuum, this model provides a mechanistic language for hypothesis generation, biomarker-guided periodization, and future experimental validation. Full article

The poly(ADP-ribose) polymerase (PARP) family constitutes a major group of proteins and enzymes essential for the maintenance of cellular homeostasis under physiological conditions and plays a pivotal role in the onset and progression of multiple pathological states. Members of the PARP family are classified into distinct subgroups based on their subcellular localization, structural organization, and ADP-ribosyltransferase activity. To date, the majority of studies have focused on DNA-dependent PARPs, owing to their well-established involvement in DNA repair mechanisms, cell cycle regulation, and diverse human pathologies. Nevertheless, over the past decade, a smaller subset of PARPs—limited in both abundance and enzymatic activity—has emerged as a critical regulator of numerous cellular processes, including embryonic development and disease progression. Within this subset, mono(ADP-ribosyl) transferases (MARTs) have gained growing attention as potential therapeutic targets in cancer, cardiovascular disorders, and neurodegenerative diseases. The ADP-ribose (ADPr) cycle, which comprises both branched poly(ADP-ribose) (PAR) polymers and mono-ADP-ribose moieties present either in free form or covalently bound to cellular substrates, is tightly regulated to ensure cellular homeostasis. This regulation relies on a finely tuned balance between ADP-ribosylation, DePARylation, and the subsequent recycling of mono-ADP-ribose. In this review, we provide a comprehensive overview of the biological roles of mono-ADP-ribosylation (MARylation) and DePARylation, with particular emphasis on their contribution to cancer-related processes. In addition, we discuss emerging evidence supporting their translational relevance and therapeutic potential. In conclusion, MARylation and DePARylation represent two increasingly recognized regulatory pathways whose expanding clinical significance highlights the need for deeper mechanistic understanding and further exploration in both basic and translational research. Full article

Background: PARP inhibitors exhibit significant lethality in tumors with BRCA1/2 mutations or homologous recombination defects; however, their clinical application is limited by the rarity of BRCA1/2 mutations, complex resistance mechanisms, and limited efficacy of monotherapy. Objective: This study aimed to investigate how Niraparib induces dysregulation of sphingolipid metabolism—particularly upregulation of the key enzyme SPHK1—in triple-negative breast cancer (TNBC) cells, and to elucidate a novel super-enhancer (SE)-mediated mechanism of Niraparib resistance. We also applied AI-based virtual screening to identify compounds targeting key nodes and develop strategies for sensitizing TNBC to Niraparib. Results: Niraparib induced sphingolipid metabolic imbalance and significantly upregulated SPHK1 in TNBC. Multi-omics analyses revealed that SPHK1 is regulated by a super-enhancer. Mechanistically, Niraparib inhibited PARylation of the transcription factor SP1, enhancing its occupancy at the SE region and reactivating its transcriptional activity, thereby promoting SPHK1 expression. This process activated pro-survival signaling pathways and conferred niraparib resistance. AI-facilitated virtual screening identified the natural compound Echinatin as a potent SP1 inhibitor, which stably binds to SP1 and exhibits marked synergistic effects with Niraparib. While targeting downstream SPHK1 also provided therapeutic benefit by enhancing the anti-tumor efficacy of Niraparib, Echinatin demonstrates a superior advantage due to its more favorable toxicity profile. Conclusions: Niraparib induces resistance through the SP1-SE-SPHK1 axis, whereas Echinatin effectively reverses this mechanism by inhibiting the upstream regulator SP1, significantly potentiating the efficacy of Niraparib. This study reveals a novel molecular mechanism underlying Niraparib resistance and proposes a promising combination therapy strategy. Full article

Poly(ADP-ribose)polymerase 1 (PARP1) is an enzyme that interacts with chromatin during DNA repair and transcription processes; the molecular mechanisms of these processes remain to be determined. Previously, we have shown that PARP1 can bind to and reorganize nucleosomes using two modes of interaction with a mono-nucleosome, which are realized through PARP1 binding to the ends of linker DNA and to the nucleosome core. Here, it is shown that the latter mode of binding induces the reorganization of nucleosome structure and is more stable under the conditions of poly(ADP-ribosyl)ation (PARylation). The initial nucleosome structure is fully recovered after the dissociation of autoPARylated PARP1. The competition between PARP1 and linker histone H1.0 for binding to a nucleosome is mediated by the PARP1-H1.0 interaction and is affected by the length of linker DNA fragments. Longer linkers stabilize H1.0-nucleosome complexes, while shorter linkers facilitate displacement of H1.0 from the chromatosome by PARP1. PARylation removes both H1.0 and PARP1 from the complexes with nucleosomes. The data suggest that the H1.0 displacement from chromatin by PARP1 that is likely modulated by the density of nucleosomes might reduce chromatin compaction and facilitate access of PARP1-dependent DNA repair and transcription factors to nucleosome and inter-nucleosomal DNA. Full article

Modified oligonucleotides (oligos) are widely used as convenient tools in many scientific fields, including biomedical applications and therapies. In particular, oligos with lipophilic groups attached to the backbone ensure penetration of the cell membrane without the need for transfection. This study examines the interaction between amphiphilic DNA duplexes, in which one of the chains contains a lipophilic substituent, and several DNA repair proteins, particularly DNA-damage-dependent PARPs, using various biochemical approaches. DNA with a lipophilic substituent (LS-DNA) demonstrates more efficient binding with DNA damage activated poly(AD-ribose) polymerases 1-3 (PARP1, PARP2, PARP3) and DNA polymerase β. Chemically reactive LS-DNA derivatives containing a photoactivatable nucleotide (photo-LS-DNAs) or a 5′ deoxyribose phosphate (dRP) group in the vicinity of double-strand breaks (DSBs) are used for the affinity labelling of PARPs and other proteins in several whole-cell extracts of human cells. In particular, photo-LS-DNAs are used to track the level of Ku antigen in the extracts of neuron-like differentiated SH-SY5Y, undifferentiated SH-SY5Y, and olfactory epithelial cells. In vitro, PARP1–PARP3 are shown to be able to slowly excise the 5′ dRP group at DSBs. LS-DNAs can activate PARP1 and PARP2 for autoPARylation, albeit less effectively than regular DNA duplexes. Full article

Poly(ADP-ribosyl)ation is a crucial posttranslational modification that governs gene expression, chromatin remodeling, and cellular homeostasis. This dynamic process is mediated by the opposing activities of poly(ADP-ribose) polymerases (PARPs), which synthesize poly(ADP-ribose) (pADPr), and poly(ADP-ribose) glycohydrolase (PARG), which degrades it. While PARP function has been extensively studied, the structural and mechanistic basis of PARG-mediated pADPr degradation remain incompletely understood. To investigate the role of PARG in pADPr metabolism, we employed CRISPR/Cas9-based genome editing to generate a novel Parg^29b mutant mouse embryonic stem cell (ESC) line carrying a precise deletion within the PARG catalytic domain. This deletion completely abolished pADPr hydrolytic activity, resulting in massive nuclear pADPr accumulation, yet ESC viability, proliferation, and cell cycle progression remained unaffected. Using Drosophila melanogaster as a model system, we demonstrated that this mutation completely disrupted the pADPr pathway and halted developmental progression, highlighting the essential role of PARG and pADPr turnover in organismal development. Our results define a critical structural determinant of PARG catalytic function, underscore the distinct requirements for pADPr metabolism in cellular versus developmental contexts, and provide a genetically tractable model for studying the regulation of poly(ADP-ribose) dynamics and therapeutic responses to PARP inhibition in vivo. Full article

The maintenance of genome stability and the prevention of genotoxic damage to DNA require immediate DNA repair. In the cell, the repair process is usually preceded by a release of DNA from complexes with chromatin proteins accompanied by nucleosome sliding, relaxing or disassembly. Base excision DNA repair (BER) corrects the most common DNA lesions, which does not disturb the DNA helix dramatically. Notably, small DNA lesions can be repaired in chromatin without global chromatin decompaction. One of the regulatory mechanisms is poly(ADP-ribosyl)ation, leading to the relaxation of the nucleosome. In our work, we demonstrated that recently a discovered protein, HPF1, can modulate the efficiency of one of the key BER stages—DNA synthesis—via the regulation of total poly(ADP-ribosyl)ation. Accordingly, we investigated both short-patch and long-patch DNA synthesis catalyzed by DNA polymerase β (pol β; main polymerase in BER) and showed that HPF1’s influence on the poly(ADP-ribosyl)ation catalyzed by PARP1 and especially by PARP2 results in more efficient DNA synthesis in the case of the short-patch BER pathway in nucleosomes. Additionally, HPF1-dependent poly(ADP-ribosyl)ation was found to positively regulate long-patch BER. Full article

Poly(ADP-ribosyl)ation (PARylation) is a dynamic protein post-translational modification (PTM) mediated by ADP-ribosyltransferases (ARTs), which regulates a plethora of essential biological processes, such as DNA repair, gene expression, and signal transduction. Among these, PAR-dependent ubiquitination (PARdU) plays a pivotal role in tagging PARylated substrates for subsequent ubiquitination and degradation events through the coordinated action of enzymes, including the E3 ligase RNF146 and the ADP-ribosyltransferase tankyrase. Notably, this pathway has emerged as a key regulator of tumorigenesis, immune modulation, and cell death. This review elucidates the molecular mechanisms of the PARdU pathway, including the RNF146–tankyrase interaction, substrate specificity, and upstream regulatory pathways. It also highlights the biological functions of PARdU in DNA damage repair, signaling pathways, and metabolic regulation, with a focus on its therapeutic potential in cancer treatment. Strategies targeting PARdU, such as tankyrase and RNF146 inhibitors, synthetic lethality approaches, and immune checkpoint regulation, offer promising avenues for precision oncology. These developments underscore the potential of PARdU as a transformative therapeutic target in combating various types of human cancer. Full article

ADP-ribosylation is a reversible modification of proteins and nucleic acids, which controls major cellular processes, including DNA damage repair, cell proliferation and differentiation, metabolism, stress, and immunity in plants and animals. The involvement of ADP-ribosylation in the life cycle of Dictyostelium and some filamentous fungi has also been demonstrated. However, the role of this process in pathogenic oomycetes has never been addressed. Here, we show that the Phytophthora infestans genome contains two PARP-like protein genes (PiPARP1 and PiPARP2), and provide evidence of PARylation activity for one of them (PiPARP2). Using dsRNA-mediated RNA silencing of the PiPARP2 gene and chemical (pharmacological) inhibition of PARP activity by 3-aminobenzamide (3AB) PARP inhibitor, we demonstrate the critical functional role of ADP-ribosylation in Phytophthora mycelium growth. Virulence test on detached leaves also suggests an important role of ADP-ribosylation in Phytophthora host plant colonisation and pathogenesis. On a practical level, our data suggest that targeting the PARylation system may constitute a novel powerful approach for the management of Phytophthora diseases. Full article

Poly(ADP-ribose) polymerases 1 and 2 (PARP1 and PARP2) play a key role in DNA repair. As major sensors of DNA damage, they are activated to produce poly(ADP-ribose). PARP1/PARP2 inhibitors have emerged as effective drugs for the treatment of cancers with BRCA deficiencies. Here, we explored aminomethylmorpholino and aminomethylmorpholino glycine nucleosides as inhibitors of PARP1 and PARP2, using different enzymatic assays. The compounds bearing thymine or 5-Br(I)-uracil bases displayed the highest inhibition potency, with all of them being more selective toward PARP1. Interaction of the inhibitors with the NAD⁺ binding cavity of PARP1 (PARP2) suggested by the mixed-type inhibition was demonstrated by molecular docking and the RoseTTAFold All-Atom AI-model. The best PARP1 inhibitors characterized by the inhibition constants in the range of 12–15 µM potentiate the cytotoxicity of hydrogen peroxide by displaying strong synergism. The inhibitors revealed no impact on PARP1/PARP2 affinity for DNA, while they reduced the dissociation rate of the enzyme–DNA complex upon the autopoly(ADP-ribosyl)ation reaction, thus providing evidence that their mechanism of action for PARP trapping is due primarily to catalytic inhibition. The most active compounds were shown to retain selectivity toward PARP1, despite the reduced inhibition potency in the presence of histone PARylation factor 1 (HPF1) capable of regulating PARP1/PARP2 catalytic activity and ADP-ribosylation reaction specificity. The inhibitors obtained seem to be promising for further research as potential drugs. Full article

ADP-ribosylation (ADPRylation) is a mechanism which post-translationally modifies proteins in eukaryotes in order to regulate a broad range of biological processes including programmed cell death, cell signaling, DNA repair, and responses to biotic and abiotic stresses. Poly(ADP-ribosyl) polymerases (PARPs) play a key role in the process of ADPRylation, which modifies target proteins by attaching ADP-ribose molecules. Here, we investigated whether and how PARP1 and PARylation modulate responses of Nicotiana benthamiana plants to methyl viologen (MV)-induced oxidative stress. It was found that the burst of reactive oxygen species (ROS), cell death, and loss of tissue viability invoked by MV in N. benthamiana leaves was significantly delayed by both the RNA silencing of the PARP1 gene and by applying the pharmacological inhibitor 3-aminobenzamide (3AB) to inhibit PARylation activity. This in turn reduced the accumulation of PARylated proteins and significantly increased the gene expression of major ROS scavenging enzymes including SOD (NbMnSOD; mitochondrial manganese SOD), CAT (NbCAT2), GR (NbGR), and APX (NbAPX5), and inhibited cell death. This mechanism may be part of a broader network that regulates plant sensitivity to oxidative stress through various genetically programmed pathways. Full article

Chondrosarcoma is a rare malignant tumor that forms in bone and cartilage. The primary treatment involves surgical removal of the tumor with a margin of healthy tissue. Especially if complete surgical removal is not possible, radiation therapy and chemotherapy are used in conjunction with surgery, but with a generally low efficiency. Ongoing researches are focused on understanding the genetic and molecular basis of chondrosarcoma following high linear energy transfer (LET) irradiation, which may lead to treatments that are more effective. The goal of this study is to evaluate the differential effects of DNA damage repair inhibitors and high LET irradiation on chondrosarcoma versus chondrocyte cells and the LET-dependency of the effects. Two chondrosarcoma cell lines with different IDH mutation status and one chondrocyte cell line were exposed to low LET (X-ray) and high LET (carbon ion) irradiation in combination with an Olaparib PARP inhibitor. Cell survival and DNA repair mechanisms were investigated. High LET irradiation drastically reduced cell survival, with a biological efficiency three times that of low LET. Olaparib significantly inhibited PARylation in all the tested cells. A significant reduction in cell survival of both chondrosarcoma and chondrocyte cells was observed following the treatment combining Olaparib and X-ray. PARP inhibition induced an increase in PARP-1 expression and a reduced effect on the cell survival of WT IDH chondrosarcoma cells. No radiosensitizing effect was observed in cells exposed to Olaparib paired with high LET irradiation. NHEJ was activated in response to high LET irradiation, neutralizing the PARP inhibition effect in both chondrosarcoma cell lines. When high LET irradiation is not available, PARP inhibition could be used in combination with low LET irradiation, with significant radiosensitizing effects on chondrosarcoma cells. Chondrocytes may be affected by the treatment combination too, showing the need to preserve normal tissues from radiation fields when this kind of treatment is suggested. Full article

Breast and ovarian cancers pose significant therapeutic challenges. We explored the synergistic cytotoxicity of histone deacetylase inhibitors (HDACis), poly(ADP-ribose) polymerase inhibitors (PARPis), and decitabine in breast (MDA-MB-231 and MCF-7) and ovarian (HEY-T30 and SKOV-3) cancer cell lines that were exposed to HDACi (panobinostat or vorinostat), PARPi (talazoparib or olaparib), decitabine, or their combinations. HDACi, PARPi, and decitabine combinations had synergistic cytotoxicity (assessed by MTT and clonogenic assays) in all cell lines (combination index < 1). Clonogenic assays confirmed the sensitivity of breast and ovarian cancer cell lines to the three-drug combinations (panobinostat, talazoparib, and decitabine; panobinostat, olaparib, and decitabine; vorinostat, talazoparib, and decitabine; vorinostat, olaparib, and decitabine). Cell proliferation was inhibited by 48–70%, and Annexin V positivity was 42–59% in all cell lines exposed to the three-drug combinations. Western blot analysis showed protein PARylation inhibition, caspase 3 and PARP1 cleavage, and c-MYC down-regulation. The three-drug combinations induced more DNA damage (increased phosphorylation of histone 2AX) than the individual drugs, impaired the DNA repair pathways, and altered the epigenetic regulation of gene expression. These results indicate that HDACi, PARPi, and decitabine combinations should be further explored in these tumor types. Further clinical validation is warranted to assess their safety and efficacy. Full article