PARP-14 functions as a transcriptional switch for Stat6-dependent gene activation

Discovery and Optimization of Potent and Highly Selective PARP14 Inhibitors for the Treatment of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic, recurrent, and inflammatory skin condition that remains challenging to treat effectively and safely with current therapies. Recent studies by multiple independent research groups have demonstrated that poly(ADP-ribose) polymerase 14 (PARP14) has been implicated in the progression of inflammatory diseases through its regulation of the Th2 and Th17 signaling pathways, leading to the identification of PARP14 as a promising therapeutic target. Herein, we report the discovery of a novel PARP14 inhibitor Q22 with exceptional inhibitory activity against PARP14 (IC50 = 5.52 nM), high selectivity toward PARP14, favorable pharmacokinetic properties, and a robust in vivo safety profile. Notably, compared to positive control RBN-3143, Q22 showed significant therapeutic efficacy in a dinitrochlorobenzene (DNCB)-induced AD mouse model by markedly reducing the expression of key AD-associated inflammatory cytokines, including IL-4, IL-13, and IL-17A. These findings suggest that Q22 holds considerable promise as a PARP14 inhibitor for AD treatment.

Interferon-induced ADP-ribosylation: technical developments driving ICAB discovery

Cells respond to a variety of internal and external stimuli by regulating the activities of different signalling cascades and cellular processes, often via chemical modifications of biological macromolecules that modulate their overall levels, biochemical activities or biophysical interactions. One such modification, termed ADP-ribosylation (ADPr), is emerging as an important player in the interferon (IFN) response, but the molecular targets and functions of ADP-ribosyltransferases within this core component of innate immunity still remains unclear. We and others have recently identified that stimulation of IFN signalling cascades promotes the formation of a novel cytosolic structure in human cells that is enriched in ADP-ribosyl modifications. Here, we propose to name these structures 'interferon-induced cytosolic ADPr bodies' (ICABs) and discuss their known components and potential functions. We also review methods to detect ICABs (and cellular ADPr in general) using a range of recently developed reagents. This lays the foundation for future studies aimed at elucidating the molecular functions of ICABs and ADPr in innate immune responses, which is a central unanswered question in the field.

Combined PARP14 inhibition and PD-1 blockade promotes cytotoxic T cell quiescence and modulates macrophage polarization in relapsed melanoma

BACKGROUND

Programmed cell death 1 (PD-1) signaling blockade by immune checkpoint inhibitors (ICI) effectively restores immune surveillance to treat melanoma. However, chronic interferon-gamma (IFNγ)-induced immune homeostatic responses in melanoma cells contribute to immune evasion and acquired resistance to ICI. Poly ADP ribosyl polymerase 14 (PARP14), an IFNγ-responsive gene product, partially mediates IFNγ-driven resistance. PARP14 inhibition prolongs PD-1 blockade responses in preclinical models, but fails to achieve full tumor clearance, suggesting the involvement of additional resistance mechanisms.

METHODS

We identified a robust PARP14 catalytic inhibitor gene signature and evaluated its association with patient survival. Using preclinical models and single-cell RNA sequencing, we investigated immune and tumor cell adaptations to PARP14 inhibition combined with PD-1 blockade.

RESULTS

Combining PARP14 inhibition and PD-1 blockade suppressed tumor-associated macrophages while increasing proinflammatory memory macrophages. Moreover, this combination mitigated the terminal exhaustion of cytotoxic T cells by inducing a quiescent state, thereby preserving functionality. Despite the enhanced immune responses, tumor cells developed adaptive resistance by engaging alternative immune evasion pathways.

CONCLUSIONS

Although adaptive resistance mechanisms re-emerge, PARP14 inhibition combined with PD-1 blockade offers a promising strategy to enhance treatment outcomes and overcome ICI resistance in melanoma, as immune cells are primed for further therapeutic interventions that leverage the quiescent state.

Agmatine attenuates the severity of immunometabolic disorders by suppressing macrophage polarization: an in vivo study using an ulcerative colitis mouse model

Agmatine, an endogenous polyamine generated by the gut microbiota, positively affects host lifespan by regulating mononuclear cell or macrophage function. Although the regulatory pathways governing monocyte/macrophage differentiation have been well studied, the influence of the microbiome and its metabolites on monocyte/macrophage function have not been fully elucidated. To address this, we aimed to investigate the mechanisms whereby agmatine inhibits immunometabolic disorders using the colon of ulcerative colitis (UC) model mice. Agmatine (10 mM) attenuated pathological damage to colonic tissue and significantly improved the survival rate of UC model mice. In particular, treatment of UC model mice with 0.4, 2, and 10 mM agmatine resulted in mortality rates of 70 %, 20 %, 10 %, and 0 %, respectively. In a macrophage-depletion model, agmatine regulated the inflammatory microenvironment by affecting macrophages: it reduced the proportion of M1 macrophages and increased that of M2 macrophages in UC model mice. In cultured macrophages, agmatine inhibited lipopolysaccharide-induced inflammatory cytokine and NO secretion, as detected by enzyme-linked immunosorbent assay and the Griess assay, respectively. Agmatine partially reduced inflammatory factor production by inhibiting histone deacetylase, as detected by fluorometric assay. These findings provide evidence that agmatine efficiently suppresses macrophage polarization in UC mice, highlighting its potential as an anti-inflammatory agent against UC.

Identification of New Single Nucleotide Polymorphisms Potentially Related to Small Ruminant Lentivirus Infection Susceptibility in Goats Based on Data Selected from High-Throughput Sequencing

Small ruminant lentivirus (SRLV) infections are spread in the flocks of sheep and goats all over the world, causing economic loss. Although only a fraction of infected animals develop disease symptoms, all of them may shed the virus, causing uncontrolled spread of the infection. Antibodies against the virus can be detected in the blood of infected animals and are the main marker of infection. Additionally, in most infected animals, proviral DNA can also be detected, but at different levels. Due to the lack of treatment or vaccines, the most effective strategy to prevent SRLV infections are control programmes introduced by several countries based on the elimination of seropositive individuals from the flock. An alternative approach, which has currently become the rationale, is an identification of host factors which may predispose certain individuals or breeds to resistance or susceptibility to small ruminant lentivirus infection. In our work, attention was paid to goats of the Carpathian breed infected with SRLV. Available RNA-seq results from the blood of 12 goats with a determined level of SRLV proviral load were used to analyse single nucleotide polymorphisms (SNPs) by the variant calling method. Six SNPs within five genes (POU2AF1, BCAT2, TMEM154, PARP14, UBASH3A) were selected for genotyping to determine their association with the level of small ruminant lentivirus proviral DNA in a group of 60 goats. Interestingly, in seronegative individuals, only the TT genotype of the PARP14 gene was observed, while the TMEM154 CC genotype was found only in seropositive goats. Both genes may be considered potential markers for resistance/susceptibility to SRLV infection. In contrast, polymorphisms identified in POU2AF1 and UBASH3A genes seemed to be deleterious for respective protein functions; therefore, these genes are less likely to be recognised as resistance/susceptibility markers of SRLV infection.

PARP enzymes and mono-ADP-ribosylation: advancing the connection from interferon-signalling to cancer biology

ADP-ribosyltransferases of the PARP family encompass a group of enzymes with variegated regulatory functions in cells, ranging from DNA damage repair to the control of cell-cycle progression and immune response. Over the years, this knowledge has led to the use of PARP1/2 inhibitors as mainstay pharmaceutical strategies for the treatment of ovarian, pancreatic, prostate and breast cancers, holding mutations in genes encoding for proteins involved in the DNA repair mechanisms (synthetic lethality). Meanwhile, the last decade has witnessed significant progress in comprehending cellular pathways regulated by mono-ADP-ribosylation, with a huge effort in the development of novel selective compounds to inhibit those PARPs endowed with mono-ADP-ribosylation activity. This review focuses on the progress achieved in the cancer field, delving into most recent findings regarding the role of a subset of enzymes - the interferon-stimulated PARPs - in cancer progression.

Body-wide genetic deficiency of poly(ADP-ribose) polymerase 14 sensitizes mice to colitis

Inflammatory bowel disease (IBD) is a chronic disease of the gastrointestinal tract affecting millions of people. Here, we investigated the expression and functions of poly(ADP-ribose) polymerase 14 (Parp14), an important regulatory protein in immune cells, with an IBD patient cohort as well as two mouse colitis models, that is, IBD-mimicking oral dextran sulfate sodium (DSS) exposure and oral Salmonella infection. Parp14 was expressed in the human colon by cells in the lamina propria, but, in particular, by the epithelial cells with a granular staining pattern in the cytosol. The same expression pattern was evidenced in both mouse models. Parp14-deficiency caused increased rectal bleeding as well as stronger epithelial erosion, Goblet cell loss, and immune cell infiltration in DSS-exposed mice. The absence of Parp14 did not affect the mouse colon bacterial microbiota. Also, the colon leukocyte populations of Parp14-deficient mice were normal. In contrast, bulk tissue RNA-Seq demonstrated that the colon transcriptomes of Parp14-deficient mice were dominated by abnormalities in inflammation and infection responses both prior and after the DSS exposure. Overall, the data indicate that Parp14 has an important role in the maintenance of colon epithelial barrier integrity. The prognostic and predictive biomarker potential of Parp14 in IBD merits further investigation.

Epigenetic regulation of hepatocellular carcinoma progression: MicroRNAs as therapeutic, diagnostic and prognostic factors

Hepatocellular carcinoma (HCC), a significant challenge for public healthcare systems in developed Western countries including the USA, Canada, and the UK, is influenced by different risk factors including hepatitis virus infections, alcoholism, and smoking. The disruption in the balance of microRNAs (miRNAs) plays a vital function in tumorigenesis, given their function as regulators in numerous signaling networks. These miRNAs, which are mature and active in the cytoplasm, work by reducing the expression of target genes through their impact on mRNAs. MiRNAs are particularly significant in HCC as they regulate key aspects of the tumor, like proliferation and invasion. Additionally, during treatment phases such as chemotherapy and radiotherapy, the levels of miRNAs are key determinants. Pre-clinical experiments have demonstrated that altered miRNA expression contributes to HCC development, metastasis, drug resistance, and radio-resistance, highlighting related molecular pathways and processes like MMPs, EMT, apoptosis, and autophagy. Furthermore, the regulatory role of miRNAs in HCC extends beyond their immediate function, as they are also influenced by other epigenetic factors like lncRNAs and circular RNAs (circRNAs), as discussed in recent reviews. Applying these discoveries in predicting the prognosis of HCC could mark a significant advancement in the therapy of this disease.

PARP14 correlates with GBM proliferation and poor prognosis by elevating expression of SAMD/SAMD9L

BACKGROUND

Glioblastoma(GBM) is the most common primary tumor of the central nervous system with an extremely dismal prognosis. Many progresses have been made such as the discovery of new molecular biomarkers and target drugs especially IDH inhibitors. However, GBM prognosis is still poor, which requires more biomarkers and drug targets for more precision classification and treatment.

MATERIALS AND METHODS

Potential prognostic biomarkers of GBM were screened by TCGA database, and ectopic up-regulation of PARP14 was identified. Expression and clinical significance of PARP14 were detected in our GBM cohort consisting of 143 patients with gross total surgical resection. Related genes with PARP14 were further screened and identified by in silico analysis and in vitro experiments. The expression and prognostic significance of SAMD9 and SAMD9L were verified with IHC and survival analysis in our cohort.

RESULTS

PARP14 was up-regulated in GBM compared with non-tumor adjacent tissues. PARP14 correlated with poor prognosis and can be regarded as an independent prognostic biomarker of GBM. PARP14 expression was positively associated with SAMD9 and SAMD9L in GBM. In GBM cells, PARP14 could increase the expression of SAMD9 and SAMD9L. SAMD9 and SAMD9L were highly expressed in high-PARP14 subset and were both prognostic biomarkers of GBM. Moreover, PARP14 increased GBM proliferation by inducing SAMD9 and SAMD9L expression.

CONCLUSIONS

PARP14, SAMD9, and SAMD9L are prognostic biomarkers of GBM predicting poor prognosis. PARP14 promotes GBM cell proliferation by inducing SAMD9 and SAMD9L expression. Our results indicate that PARP14/SAMD9/SAMD9L are prognostic biomarkers and potential drug targets of GBM.

KH-like Domains in PARP9/DTX3L and PARP14 Coordinate Protein-Protein Interactions to Promote Cancer Cell Survival

Certain members of the ADP-ribosyltransferase superfamily (ARTD or PARP enzymes) catalyse ADP-ribosylation in response to cellular stress, DNA damage and viral infection and are upregulated in various tumours. PARP9, its binding partner DTX3L and PARP14 protein levels are significantly correlated in head and neck squamous cell carcinoma (HNSCC) and other tumour types though a mechanism where PARP9/DTX3L regulates PARP14 post-transcriptionally. Depleting PARP9, DTX3L or PARP14 expression in HNSCC or HeLa cell lines decreases cell survival through a reduction of proliferation and an increase in apoptosis. A partial rescue of survival was achieved by expressing a PARP14 truncation containing a predicted eukaryotic type I KH domain. KH-like domains were also found in PARP9 and in DTX3L and contributed to protein-protein interactions between PARP9-DTX3L and PARP14-DTX3L. Homodimerization of DTX3L was also coordinated by a KH-like domain and was disrupted by site-specific mutation. Although, cell survival promoted by PARP14 did not require ADP-ribosyltransferase activity, interaction of DTX3L in vitro suppressed PARP14 auto-ADP-ribosylation and promoted trans-ADP-ribosylation of PARP9 and DTX3L. In summary, we characterised PARP9-DTX3L-PARP14 interactions important to pro-survival signalling in HNSCC cells, albeit in PARP14 catalytically independent fashion.

Human germline gain-of-function in STAT6: from severe allergic disease to lymphoma and beyond

Signal transducer and activator of transcription (STAT)-6 is a transcription factor central to pro-allergic immune responses, although the function of human STAT6 at the whole-organism level has long remained unknown. Germline heterozygous gain-of-function (GOF) rare variants in STAT6 have been recently recognized to cause a broad and severe clinical phenotype of early-onset, multi-system allergic disease. Here, we provide an overview of the clinical presentation of STAT6-GOF disease, discussing how dysregulation of the STAT6 pathway causes severe allergic disease, and identifying possible targeted treatment approaches. Finally, we explore the mechanistic overlap between STAT6-GOF disease and other monogenic atopic disorders, and how this group of inborn errors of immunity (IEIs) powerfully inform our fundamental understanding of common human allergic disease.

Exploration of glycosyltransferases mutation status in cervical cancer reveals PARP14 as a potential prognostic marker

This study investigates the potential role of Glycosyltransferases (GTs) in the glycosylation process and their association with malignant tumors. Specifically, the study focuses on PARP14, a member of GTs, and its potential as a target for tumors in the diagnosis and treatment of cervical cancer. To gather data, the study used somatic mutation data, gene expression data and clinical information from TCGA-CESE dataset as well as tissue samples from cervical cancer patients. Further verification was conducted through RT-qPCR and immunohistochemistry staining on cervical cancer tissues to confirm the expression of PARP14. The study utilized Kaplan-Meier for survival analysis of cervical cancer patient and found significant mutational abnormalities in GTs. The high frequency mutated gene was identified as PARP14. RT-qPCR revealed significantly higher mRNA expression of PARP14 compared to precancerous tissue. Using IHC combined with Kaplan-Meier,patients in the PARP14 high expression group had a better prognosis than the low expression group. The study identified PARP14 as a frequently mutated gene in cervical cancer and proposed its potential role in diagnosis and treatment.

PARP14 inhibition restores PD-1 immune checkpoint inhibitor response following IFNγ-driven acquired resistance in preclinical cancer models

Resistance mechanisms to immune checkpoint blockade therapy (ICBT) limit its response duration and magnitude. Paradoxically, Interferon γ (IFNγ), a key cytokine for cellular immunity, can promote ICBT resistance. Using syngeneic mouse tumour models, we confirm that chronic IFNγ exposure confers resistance to immunotherapy targeting PD-1 (α-PD-1) in immunocompetent female mice. We observe upregulation of poly-ADP ribosyl polymerase 14 (PARP14) in chronic IFNγ-treated cancer cell models, in patient melanoma with elevated IFNG expression, and in melanoma cell cultures from ICBT-progressing lesions characterised by elevated IFNγ signalling. Effector T cell infiltration is enhanced in tumours derived from cells pre-treated with IFNγ in immunocompetent female mice when PARP14 is pharmacologically inhibited or knocked down, while the presence of regulatory T cells is decreased, leading to restoration of α-PD-1 sensitivity. Finally, we determine that tumours which spontaneously relapse in immunocompetent female mice following α-PD-1 therapy upregulate IFNγ signalling and can also be re-sensitised upon receiving PARP14 inhibitor treatment, establishing PARP14 as an actionable target to reverse IFNγ-driven ICBT resistance.

PARP14 is a PARP with both ADP-ribosyl transferase and hydrolase activities

PARP14 is a mono-ADP-ribosyl transferase involved in the control of immunity, transcription, and DNA replication stress management. However, little is known about the ADP-ribosylation activity of PARP14, including its substrate specificity or how PARP14-dependent ADP-ribosylation is reversed. We show that PARP14 is a dual-function enzyme with both ADP-ribosyl transferase and hydrolase activity acting on both protein and nucleic acid substrates. In particular, we show that the PARP14 macrodomain 1 is an active ADP-ribosyl hydrolase. We also demonstrate hydrolytic activity for the first macrodomain of PARP9. We reveal that expression of a PARP14 mutant with the inactivated macrodomain 1 results in a marked increase in mono(ADP-ribosyl)ation of proteins in human cells, including PARP14 itself and antiviral PARP13, and displays specific cellular phenotypes. Moreover, we demonstrate that the closely related hydrolytically active macrodomain of SARS2 Nsp3, Mac1, efficiently reverses PARP14 ADP-ribosylation in vitro and in cells, supporting the evolution of viral macrodomains to counteract PARP14-mediated antiviral response.

Privileged Scaffolds for Potent and Specific Inhibitors of Mono-ADP-Ribosylating PARPs

The identification of new targets to address unmet medical needs, better in a personalized way, is an urgent necessity. The introduction of PARP1 inhibitors into therapy, almost ten years ago, has represented a step forward this need being an innovate cancer treatment through a precision medicine approach. The PARP family consists of 17 members of which PARP1 that works by poly-ADP ribosylating the substrate is the sole enzyme so far exploited as therapeutic target. Most of the other members are mono-ADP-ribosylating (mono-ARTs) enzymes, and recent studies have deciphered their pathophysiological roles which appear to be very extensive with various potential therapeutic applications. In parallel, a handful of mono-ARTs inhibitors emerged that have been collected in a perspective on 2022. After that, additional very interesting compounds were identified highlighting the hot-topic nature of this research field and prompting an update. From the present review, where we have reported only mono-ARTs inhibitors endowed with the appropriate profile of pharmacological tools or drug candidate, four privileged scaffolds clearly stood out that constitute the basis for further drug discovery campaigns.

Poly(ADP-ribose) polymerase family member 14 promotes functional recovery after spinal cord injury through regulating microglia M1/M2 polarization via STAT1/6 pathway

Poly(ADP-ribose)polymerase family member 14 (PARP14), which is an intracellular mono(ADP-ribosyl) transferase, has been reported to promote post-stroke functional recovery, but its role in spinal cord injury (SCI) remains unclear. To investigate this, a T10 spinal cord contusion model was established in C57BL/6 mice, and immediately after the injury PARP14 shRNA-carrying lentivirus was injected 1 mm from the injury site to silence PARP14 expression. We found that PARP14 was up-regulated in the injured spinal cord and that lentivirus-mediated downregulation of PARP14 aggravated functional impairment after injury, accompanied by obvious neuronal apoptosis, severe neuroinflammation, and slight bone loss. Furthermore, PARP14 levels were elevated in microglia after SCI, PARP14 knockdown activated microglia in the spinal cord and promoted a shift from M2-polarized microglia (anti-inflammatory phenotype) to M1-polarized microglia (pro-inflammatory phenotype) that may have been mediated by the signal transducers and activators of transcription (STAT) 1/6 pathway. Next, microglia M1 and M2 polarization were induced in vitro using lipopolysaccharide/interferon-γ and interleukin-4, respectively. The results showed that PARP14 knockdown promoted microglia M1 polarization, accompanied by activation of the STAT1 pathway. In addition, PARP14 overexpression made microglia more prone to M2 polarization and further activated the STAT6 pathway. In conclusion, these findings suggest that PARP14 may improve functional recovery after SCI by regulating the phenotypic transformation of microglia via the STAT1/6 pathway.

PARPs and ADP-Ribosylation in Chronic Inflammation: A Focus on Macrophages

Aberrant adenosine diphosphate-ribose (ADP)-ribosylation of proteins and nucleic acids is associated with multiple disease processes such as infections and chronic inflammatory diseases. The poly(ADP-ribose) polymerase (PARP)/ADP-ribosyltransferase (ART) family members promote mono- or poly-ADP-ribosylation. Although evidence has linked PARPs/ARTs and macrophages in the context of chronic inflammation, the underlying mechanisms remain incompletely understood. This review provides an overview of literature focusing on the roles of PARP1/ARTD1, PARP7/ARTD14, PARP9/ARTD9, and PARP14/ARTD8 in macrophages. PARPs/ARTs regulate changes in macrophages during chronic inflammatory processes not only via catalytic modifications but also via non-catalytic mechanisms. Untangling complex mechanisms, by which PARPs/ARTs modulate macrophage phenotype, and providing molecular bases for the development of new therapeutics require the development and implementation of innovative technologies.

[1,2,4]Triazolo[3,4-b]benzothiazole Scaffold as Versatile Nicotinamide Mimic Allowing Nanomolar Inhibition of Different PARP Enzymes

We report [1,2,4]triazolo[3,4-b]benzothiazole (TBT) as a new inhibitor scaffold, which competes with nicotinamide in the binding pocket of human poly- and mono-ADP-ribosylating enzymes. The binding mode was studied through analogues and cocrystal structures with TNKS2, PARP2, PARP14, and PARP15. Based on the substitution pattern, we were able to identify 3-amino derivatives 21 (OUL243) and 27 (OUL232) as inhibitors of mono-ARTs PARP7, PARP10, PARP11, PARP12, PARP14, and PARP15 at nM potencies, with 27 being the most potent PARP10 inhibitor described to date (IC₅₀ of 7.8 nM) and the first PARP12 inhibitor ever reported. On the contrary, hydroxy derivative 16 (OUL245) inhibits poly-ARTs with a selectivity toward PARP2. The scaffold does not possess inherent cell toxicity, and the inhibitors can enter cells and engage with the target protein. This, together with favorable ADME properties, demonstrates the potential of TBT scaffold for future drug development efforts toward selective inhibitors against specific enzymes.

Promotion of a synthetic degradation of activated STAT6 by PARP-1 inhibition: roles of poly(ADP-ribosyl)ation, calpains and autophagy

Background

We reported that PARP-1 regulates genes whose products are crucial for asthma, in part, by controlling STAT6 integrity speculatively through a calpain-dependent mechanism. We wished to decipher the PARP-1/STAT6 relationship in the context of intracellular trafficking and promoter occupancy of the transcription factor on target genes, its integrity in the presence of calpains, and its connection to autophagy.

Methods

This study was conducted using primary splenocytes or fibroblasts derived from wild-type or PARP-1^−/− mice and Jurkat T cells to mimic Th2 inflammation.

Results

We show that the role for PARP-1 in expression of IL-4-induced genes (e.g. gata-3) in splenocytes did not involve effects on STAT6 phosphorylation or its subcellular trafficking, rather, it influenced its occupancy of gata-3 proximal and distal promoters in the early stages of IL-4 stimulation. At later stages, PARP-1 was crucial for STAT6 integrity as its inhibition, pharmacologically or by gene knockout, compromised the fate of the transcription factor. Calpain-1 appeared to preferentially degrade JAK-phosphorylated-STAT6, which was blocked by calpastatin-mediated inhibition or by genetic knockout in mouse fibroblasts. The STAT6/PARP-1 relationship entailed physical interaction and modification by poly(ADP-ribosyl)ation independently of double-strand-DNA breaks. Poly(ADP-ribosyl)ation protected phosphorylated-STAT6 against calpain-1-mediated degradation. Additionally, our results show that STAT6 is a bonafide substrate for chaperone-mediated autophagy in a selective and calpain-dependent manner in the human Jurkat cell-line. The effects were partially blocked by IL-4 treatment and PARP-1 inhibition.

Conclusions

The results demonstrate that poly(ADP-ribosyl)ation plays a critical role in protecting activated STAT6 during Th2 inflammation, which may be synthetically targeted for degradation by inhibiting PARP-1.

PARP14 is a novel target in STAT6 mutant follicular lymphoma

The variable clinical course of follicular lymphoma (FL) is determined by the molecular heterogeneity of tumor cells and complex interactions within the tumor microenvironment (TME). IL-4 producing follicular helper T cells (TFH) are critical components of the FL TME. Binding of IL-4 to IL-4R on FL cells activates JAK/STAT signaling. We identified STAT6 mutations (STAT6MUT) in 13% of FL (N = 33/258), all clustered within the DNA binding domain. Gene expression data and immunohistochemistry showed upregulation of IL-4/STAT6 target genes in STAT6MUT FL, including CCL17, CCL22, and FCER2 (CD23). Functionally, STAT6MUT was gain-of-function by serial replating phenotype in pre-B CFU assays. Expression of STAT6MUT enhanced IL-4 induced FCER2/CD23, CCL17 and CCL22 expression and was associated with nuclear accumulation of pSTAT6. RNA sequencing identified PARP14 -a transcriptional switch and co-activator of STAT6- among the top differentially upregulated genes in IL-4 stimulated STAT6MUT lymphoma cells and in STAT6MUT primary FL cells. Quantitative chromatin immunoprecipitation (qChIP) demonstrated binding of STAT6MUT but not STAT6WT to the PARP14 promotor. Reporter assays showed increased IL-4 induced transactivation activity of STAT6MUT at the PARP14 promotor, suggesting a self-reinforcing regulatory circuit. Knock-down of PARP14 or PARP-inhibition abrogated the STAT6MUT gain-of-function phenotype. Thus, our results identify PARP14 as a novel therapeutic target in STAT6MUT FL.

The KU-PARP14 axis differentially regulates DNA resection at stalled replication forks by MRE11 and EXO1

Suppression of nascent DNA degradation has emerged as an essential role of the BRCA pathway in genome protection. In BRCA-deficient cells, the MRE11 nuclease is responsible for both resection of reversed replication forks, and accumulation of single stranded DNA gaps behind forks. Here, we show that the mono-ADP-ribosyltransferase PARP14 is a critical co-factor of MRE11. PARP14 is recruited to nascent DNA upon replication stress in BRCA-deficient cells, and through its catalytic activity, mediates the engagement of MRE11. Loss or inhibition of PARP14 suppresses MRE11-mediated fork degradation and gap accumulation, and promotes genome stability and chemoresistance of BRCA-deficient cells. Moreover, we show that the KU complex binds reversed forks and protects them against EXO1-catalyzed degradation. KU recruits the PARP14-MRE11 complex, which initiates partial resection to release KU and allow long-range resection by EXO1. Our work identifies a multistep process of nascent DNA processing at stalled replication forks in BRCA-deficient cells.

Protection of replication forks against nucleolytic degradation is crucial for genome stability. Here, Dhoonmoon et al identify PARP14 and the KU complex as essential regulators of fork degradation by MRE11 and EXO1 nucleases in BRCA-deficient cells.

Functional roles of ADP-ribosylation writers, readers and erasers

ADP-ribosylation is a reversible post-translational modification (PTM) tightly regulated by the dynamic interplay between its writers, readers and erasers. As an intricate and versatile PTM, ADP-ribosylation plays critical roles in various physiological and pathological processes. In this review, we discuss the major players involved in the ADP-ribosylation cycle, which may facilitate the investigation of the ADP-ribosylation function and contribute to the understanding and treatment of ADP-ribosylation associated disease.

Medicinal Chemistry Perspective on Targeting Mono-ADP-Ribosylating PARPs with Small Molecules

Major advances have recently defined functions for human mono-ADP-ribosylating PARP enzymes (mono-ARTs), also opening up potential applications for targeting them to treat diseases. Structural biology combined with medicinal chemistry has allowed the design of potent small molecule inhibitors which typically bind to the catalytic domain. Most of these inhibitors are at the early stages, but some have already a suitable profile to be used as chemical tools. One compound targeting PARP7 has even progressed to clinical trials. In this review, we collect inhibitors of mono-ARTs with a typical "H-Y-Φ" motif (Φ = hydrophobic residue) and focus on compounds that have been reported as active against one or a restricted number of enzymes. We discuss them from a medicinal chemistry point of view and include an analysis of the available crystal structures, allowing us to craft a pharmacophore model that lays the foundation for obtaining new potent and more specific inhibitors.

Research Progress on Mono-ADP-Ribosyltransferases in Human Cell Biology

ADP-ribosylation is a well-established post-translational modification that is inherently connected to diverse processes, including DNA repair, transcription, and cell signaling. The crucial roles of mono-ADP-ribosyltransferases (mono-ARTs) in biological processes have been identified in recent years by the comprehensive use of genetic engineering, chemical genetics, and proteomics. This review provides an update on current methodological advances in the study of these modifiers. Furthermore, the review provides details on the function of mono ADP-ribosylation. Several mono-ARTs have been implicated in the development of cancer, and this review discusses the role and therapeutic potential of some mono-ARTs in cancer.

The Activated Macrophage - A Tough Fortress for Virus Invasion: How Viruses Strike Back

Macrophages (Mφ) are innate immune cells with a variety of functional phenotypes depending on the cytokine microenvironment they reside in. Mφ exhibit distinct activation patterns that are found within a wide array of activation states ranging from the originally discovered classical pro-inflammatory (M1) to the anti-inflammatory (M2) with their multi-facades. M1 cells are induced by IFNγ + LPS, while M2 are further subdivided into M2a (IL-4), M2b (Immune Complex) and M2c (IL-10) based on their inducing stimuli. Not surprisingly, Mφ activation influences the outcome of viral infections as they produce cytokines that in turn activate cells of the adaptive immune system. Generally, activated M1 cells tend to restrict viral replication, however, influenza and HIV exploit inflammation to support their replication. Moreover, M2a polarization inhibits HIV replication at the post-integration level, while HCMV encoded hrIL-10 suppresses inflammatory reactions by facilitating M2c formation. Additionally, viruses such as LCMV and Lassa Virus directly suppress Mφ activation leading to viral chronicity. Here we review how Mφ activation affects viral infection and the strategies by which viruses manipulate Mφ polarization to benefit their own fitness. An understanding of these mechanisms is important for the development of novel immunotherapies that can sway Mφ phenotype to inhibit viral replication.

Research Advances in the Role of the Poly ADP Ribose Polymerase Family in Cancer

Poly ADP ribose polymerases (PARPs) catalyze the modification of acceptor proteins, DNA, or RNA with ADP-ribose, which plays an important role in maintaining genomic stability and regulating signaling pathways. The rapid development of PARP1/2 inhibitors for the treatment of ovarian and breast cancers has advanced research on other PARP family members for the treatment of cancer. This paper reviews the role of PARP family members (except PARP1/2 and tankyrases) in cancer and the underlying regulatory mechanisms, which will establish a molecular basis for the clinical application of PARPs in the future.

Immune Metabolism of IL-4-Activated B Cells and Th2 Cells in the Context of Allergic Diseases

Over the last decades, the frequency of allergic disorders has steadily increased. Immunologically, allergies are caused by abnormal immune responses directed against otherwise harmless antigens derived from our environment. Two of the main cell types driving allergic sensitization and inflammation are IgE-producing plasma cells and Th2 cells. The acute activation of T and B cells, their differentiation into effector cells, as well as the formation of immunological memory are paralleled by distinct changes in cellular metabolism. Understanding the functional consequences of these metabolic changes is the focus of a new research field termed "immune metabolism". Currently, the contribution of metabolic changes in T and B cells to either the development or maintenance of allergies is not completely understood. Therefore, this mini review will introduce the fundamentals of energy metabolism, its connection to immune metabolism, and subsequently focus on the metabolic phenotypes of IL-4-activated B cells and Th2 cells.

Hsa_circ_0016788 regulates hepatocellular carcinoma progression via miR-506-3p/poly-adenosine diphosphate-ribose polymerase

BACKGROUND AND AIM

Hepatocellular carcinoma (HCC) is a common malignant tumor worldwide. Recent researches have shown that circular RNAs (circRNAs) could affect the progress of HCC, but the mechanism is still indistinct. In this work, we explored the roles of circRNA_0016788 in HCC.

METHODS

The levels of hsa_circ_0016788, microRNA-506-3p (miR-506-3p), and mRNA of poly-adenosine diphosphate-ribose polymerase, member 14 (PARP14) were detected by quantitative real-time reverse transcription-polymerase chain reaction in HCC tissues. Meanwhile, the level of PARP14 was quantified by Western blot analysis. Besides, the cell functions were examined by commercial kit, Cell Counting Kit-8 assay, EdU assay, colony formation assay, flow cytometry assay, Western blot, and transwell assay. Furthermore, the interplay between miR-506-3p and hsa_circ_0016788 or PARP14 was detected by dual-luciferase reporter assay. Eventually, the in vivo experiments were applied to measure the role of hsa_circ_0016788.

RESULTS

The levels of hsa_circ_0016788 and PARP14 were upregulated, and the miR-506-3p level was decreased in HCC tissues in contrast to that in normal tissues. For functional analysis, hsa_circ_0016788 deficiency inhibited cell glycolysis metabolism, cell vitality, cell proliferation, colony formation, and invasion in HCC cells whereas promoted cell apoptosis. Moreover, miR-506-3p was confirmed to repress the progression of HCC cells by suppressing PARP14. In mechanism, hsa_circ_0016788 acted as a miR-506-3p sponge to regulate the level of PARP14. In addition, hsa_circ_0016788 knockdown also inhibited tumor growth in vivo.

CONCLUSION

Hsa_circ_0016788 facilitates the development of HCC through increasing PARP14 expression by regulating miR-506-3p, which also offered an underlying targeted therapy for HCC treatment.

Interplay between ADP-ribosyltransferases and essential cell signaling pathways controls cellular responses

Signaling cascades provide integrative and interactive frameworks that allow the cell to respond to signals from its environment and/or from within the cell itself. The dynamic regulation of mammalian cell signaling pathways is often modulated by cascades of protein post-translational modifications (PTMs). ADP-ribosylation is a PTM that is catalyzed by ADP-ribosyltransferases and manifests as mono- (MARylation) or poly- (PARylation) ADP-ribosylation depending on the addition of one or multiple ADP-ribose units to protein substrates. ADP-ribosylation has recently emerged as an important cell regulator that impacts a plethora of cellular processes, including many intracellular signaling events. Here, we provide an overview of the interplay between the intracellular diphtheria toxin-like ADP-ribosyltransferase (ARTD) family members and five selected signaling pathways (including NF-κB, JAK/STAT, Wnt-β-catenin, MAPK, PI3K/AKT), which are frequently described to control or to be controlled by ADP-ribosyltransferases and how these interactions impact the cellular responses.

NAD+ Degrading Enzymes, Evidence for Roles During Infection

Declines in cellular nicotinamide adenine dinucleotide (NAD) contribute to metabolic dysfunction, increase susceptibility to disease, and occur as a result of pathogenic infection. The enzymatic cleavage of NAD⁺ transfers ADP-ribose (ADPr) to substrate proteins generating mono-ADP-ribose (MAR), poly-ADP-ribose (PAR) or O-acetyl-ADP-ribose (OAADPr). These important post-translational modifications have roles in both immune response activation and the advancement of infection. In particular, emergent data show viral infection stimulates activation of poly (ADP-ribose) polymerase (PARP) mediated NAD⁺ depletion and stimulates hydrolysis of existing ADP-ribosylation modifications. These studies are important for us to better understand the value of NAD⁺ maintenance upon the biology of infection. This review focuses specifically upon the NAD⁺ utilising enzymes, discusses existing knowledge surrounding their roles in infection, their NAD⁺ depletion capability and their influence within pathogenic infection.

Chemical genetic methodologies for identifying protein substrates of PARPs

Poly-ADP-ribose-polymerases (PARPs) are a family of 17 enzymes that regulate a diverse range of cellular processes in mammalian cells. PARPs catalyze the transfer of ADP-ribose from NAD⁺ to target molecules, most prominently amino acids on protein substrates, in a process known as ADP-ribosylation. Identifying the direct protein substrates of individual PARP family members is an essential first step for elucidating the mechanism by which PARPs regulate a particular pathway in cells. Two distinct chemical genetic (CG) strategies have been developed for identifying the direct protein substrates of individual PARP family members. In this review, we discuss the design principles behind these two strategies and how target identification has provided novel insight into the cellular function of individual PARPs and PARP-mediated ADP-ribosylation.

Transcriptional regulation of T cell metabolism and metabolic control of T cell gene expression

T cells undergo activation, maturation, and differentiation in which they can substantially transform and restructure. This includes metabolic adaptations which have been well recognized to be specific for T cell subsets. T cell subset-specific metabolism is thought to reflect different bioenergetic requirements as well as adaptations to environmental conditions in which the T cells operate. The metabolic changes that occur in T cells are orchestrated by signaling cascades that lead to rapid post-translational changes and through transcription factors which facilitate more long-term adaptations. In addition, metabolites produced within T cells or taken up from the environment can influence gene expression by altering chromatin accessibility or the effectiveness of transcription factors through post-translational modifications, and thus act as transcription regulators in their own right.

Can molecular mimicry explain the cytokine storm of SARS-CoV-2?: An in silico approach

PARP14 and PARP9 play a key role in macrophage immune regulation. SARS‐CoV‐2 is an emerging viral disease that triggers hyper‐inflammation known as a cytokine storm. In this study, using in silico tools, we hypothesize about the immunological phenomena of molecular mimicry between SARS‐CoV‐2 Nsp3 and the human PARP14 and PARP9. The results showed an epitope of SARS‐CoV‐2 Nsp3 protein that contains consensus sequences for both human PARP14 and PARP9 that are antigens for MHC Classes 1 and 2, which can potentially induce an immune response against human PARP14 and PARP9; while its depletion causes a hyper‐inflammatory state in SARS‐CoV‐2 patients.

Molecular mimicry could produce an inflammatory state in SARS‐CoV‐2 patients.

Human PARP14 and PARP9 are the proteins involves in this phenomena.

Targeted Degradation of PARP14 Using a Heterobifunctional Small Molecule

PARP14 is an interferon-stimulated gene that is overexpressed in multiple tumor types, influencing pro-tumor macrophage polarization as well as suppressing the antitumor inflammation response by modulating IFN-γ and IL-4 signaling. PARP14 is a 203 kDa protein that possesses a catalytic domain responsible for the transfer of mono-ADP-ribose to its substrates. PARP14 also contains three macrodomains and a WWE domain which are binding modules for mono-ADP-ribose and poly-ADP-ribose, respectively, in addition to two RNA recognition motifs. Catalytic inhibitors of PARP14 have been shown to reverse IL-4 driven pro-tumor gene expression in macrophages, however it is not clear what roles the non-enzymatic biomolecular recognition motifs play in PARP14-driven immunology and inflammation. To further understand this, we have discovered a heterobifunctional small molecule designed based on a catalytic inhibitor of PARP14 that binds in the enzyme's NAD⁺ -binding site and recruits cereblon to ubiquitinate it and selectively target it for degradation.

Exome hits demystified: The next frontier

Severe mental illnesses such as schizophrenia and bipolar disorder have complex inheritance patterns, involving both common and rare variants. Whole exome sequencing is a promising approach to find out the rare genetic variants. We had previously reported several rare variants in multiplex families with severe mental illnesses. The current article tries to summarise the biological processes and pattern of expression of genes harbouring the aforementioned variants, linking them to known clinical manifestations through a methodical narrative review. Of the 28 genes considered for this review from 7 families with multiple affected individuals, 6 genes are implicated in various neuropsychiatric manifestations including some variations in the brain morphology assessed by magnetic resonance imaging. Another 15 genes, though associated with neuropsychiatric manifestations, did not have established brain morphological changes whereas the remaining 7 genes did not have any previously recorded neuropsychiatric manifestations at all. Wnt/b-catenin signaling pathway was associated with 6 of these genes and PI3K/AKT, calcium signaling, ERK, RhoA and notch signaling pathways had at least 2 gene associations. We present a comprehensive review of biological and clinical knowledge about the genes previously reported in multiplex families with severe mental illness. A 'disease in dish approach' can be helpful to further explore the fundamental mechanisms.

The Antiviral Activities of Poly-ADP-Ribose Polymerases

The poly-adenosine diphosphate (ADP)-ribose polymerases (PARPs) are responsible for ADP-ribosylation, a reversible post-translational modification involved in many cellular processes including DNA damage repair, chromatin remodeling, regulation of translation and cell death. In addition to these physiological functions, recent studies have highlighted the role of PARPs in host defenses against viruses, either by direct antiviral activity, targeting certain steps of virus replication cycle, or indirect antiviral activity, via modulation of the innate immune response. This review focuses on the antiviral activity of PARPs, as well as strategies developed by viruses to escape their action.

Analysis of Mono-ADP-Ribosylation Levels in Human Colorectal Cancer

BACKGROUND

Colorectal cancer remains a major public health problem with high morbidity and mortality rates. In the search for the mechanisms of colorectal cancer occurrence and development, increasing attention has been focused on epigenetics. The overall level of Mono-ADP-ribosylation, an epigenetic, has not been investigated now. The aim of our study was to analysis of the overall level of mono-ADP-ribosylation in colorectal cancer.

METHODS

Immunohistochemistry was used to investigate the level of mono-ADP-ribosylation in colorectal cancer and normal colorectal adjacent tissue from 64 CRC patients. The data of patient demographic, clinical and pathological characteristics were acquired and analyzed.

RESULTS

Mono-ADP-ribosylation was present in both colorectal adenocarcinoma and normal colorectal tissue. The overall level of mono-ADP-ribosylation in colorectal cancer was significantly higher than that in normal colorectal adjacent tissue. In the nucleus, the majority of samples in the high-level group were colorectal adenocarcinoma (55/64), but the opposite was true for normal colorectal tissues (7/32). In particular, increases in the level of mono-ADP-ribosylation in the cytoplasm of colorectal cancer cells was associated with a greater invasion depth of the tumor.

CONCLUSION

The increased level of mono-ADP-ribosylation in colorectal cancer enhances tumor invasion, which suggests that mono-ADP-ribosylation is involved in the development of colorectal cancer and may become a new direction to solve the problem of colorectal cancer.

A potent and selective PARP14 inhibitor decreases protumor macrophage gene expression and elicits inflammatory responses in tumor explants

PARP14 has been implicated by genetic knockout studies to promote protumor macrophage polarization and suppress the antitumor inflammatory response due to its role in modulating interleukin-4 (IL-4) and interferon-γ signaling pathways. Here, we describe structure-based design efforts leading to the discovery of a potent and highly selective PARP14 chemical probe. RBN012759 inhibits PARP14 with a biochemical half-maximal inhibitory concentration of 0.003 μM, exhibits >300-fold selectivity over all PARP family members, and its profile enables further study of PARP14 biology and disease association both in vitro and in vivo. Inhibition of PARP14 with RBN012759 reverses IL-4-driven protumor gene expression in macrophages and induces an inflammatory mRNA signature similar to that induced by immune checkpoint inhibitor therapy in primary human tumor explants. These data support an immune suppressive role of PARP14 in tumors and suggest potential utility of PARP14 inhibitors in the treatment of cancer.

The roles of STAT6 in regulating B cell fate, activation, and function

Signal transducers and activators of transcription (STATs) family of proteins are the key signal molecules in the JAK-STAT classical activation pathway of cell biology. STAT6, as a member of the STATs family, is principally activated by IL-4 and IL-13. In addition to Th2 cell differentiation, it plays a crucial role in promoting the development, differentiation, and class switching of B cells. STAT6 deficiency leads to impaired immune function, decreased glycolysis, and morphological changes in B cells, which will help develop various diseases. In this review, we will systematically summarize the major findings of how STAT6 regulates B cells to reveal the potential of STAT6 in treating human diseases.

Alternative activation of human macrophages enhances tissue factor expression and production of extracellular vesicles

Macrophages are versatile cells that can be polarized by the tissue environment to fulfill required needs. Proinflammatory polarization is associated with increased tissue degradation and propagation of inflammation whereas alternative polarization within a Th2 cytokine environment is associated with wound healing and angiogenesis. To understand whether polarization of macrophages can lead to a procoagulant macrophage subset we polarized human monocyte-derived macrophages to proinflammatory and alternative activation states. Alternative polarization with interleukin-4 and interleukin-13 led to a macrophage phenotype characterized by increased tissue factor (TF) production and release and by an increase in extracellular vesicle production. In addition, TF activity was enhanced in extracellular vesicles of alternatively polarized macrophages. This TF induction was dependent on signal transducer and activator of transcription- 6 signaling and poly ADP ribose polymerase activity. In contrast to monocytes, human macrophages did not show increased TF expression upon stimulation with lipopolysaccharide and interferon-γ. Previous polarization to either a proinflammatory or an alternative activation subset did not change the subsequent stimulation of TF. The inability of proinflammatory activated macrophages to respond to lipopolysaccharide and interferon- γ with an increase in TF production seemed to be due to an increase in TF promoter methylation and was reversible when these macrophages were treated with a demethylating agent. In conclusion, we provide evidence that proinflammatory polarization of macrophages does not lead to enhanced procoagulatory function, whereas alternative polarization of macrophages leads to an increased expression of TF and increased production of TF-bearing extracellular vesicles by these cells suggesting a procoagulatory phenotype of alternatively polarized macrophages.

Regulation of the humoral type 2 immune response against allergens and helminths

The type 2 immune response is associated with helminth infections and allergic inflammation where antibody production of the IgG1 and IgE isotypes can elicit protective or proinflammatory functions. Studies over the past few years revealed important new insights regarding the regulatory mechanisms orchestrating the humoral type 2 immune response. This includes investigations on B-cell extrinsic signals, such IL-4 and IL-21, derived from different T-helper cell subsets or discovery of new follicular helper T cells with regulatory or IgE-promoting activities. In addition, studies on B-cell intrinsic factors required for germinal center formation and class switch recombination, including the transcription factors STAT3, STAT6, and BCL-6, led to a better understanding of these processes in type 2 immune responses. Here, we review the current understanding of mechanisms controlling humoral type 2 immunity in vivo including the generation of IgE-producing plasma cells and the memory IgE response.

PARP14 inhibits microglial activation via LPAR5 to promote post-stroke functional recovery

Stroke is a major public health problem leading to high rates of death and disability worldwide, but no effective pharmacological therapy is currently available except for the use of PLAT (plasminogen activator, tissue). Here we show that PARP14 (poly (ADP-ribose) polymerase family, member 14) level was significantly increased in the peri-infarct zone of photothrombotic stroke (PT) mice. Genetic knockdown and pharmacological inhibition of PARP14 aggravated functional impairment and increased infarct volume in PT mice, while overexpression of PARP14 displayed the opposite effects. Furthermore, PARP14 was abundant in microglia, and downregulation of PARP14 increased post-stroke microglial activation, whereas overexpression of PARP14 alleviated microglial activation, possibly through microglial macroautophagy/autophagy modulation. Mechanistically, overexpression of PARP14 suppressed Lpar5 (lysophosphatidic acid receptor 5) gene transcription to inhibit microglial activation post stroke. Taken together, PARP14 is a stroke-induced signal that restricts microglial activation and promotes functional recovery, and can serve as a novel target to develop new therapeutic agents for stroke. Moreover, these findings may be conducive to proper use of various PARP inhibitors.Abbreviations: 3-MA: 3-methyladenine; AIF1/Iba-1: allograft inflammatory factor 1; CNS: central nervous system; CQ: chloroquine; DAPI: 4',6-diamidino-2-phenylindole; DMEM: Dulbecco's modified Eagle's medium; DMSO: dimethyl sulfoxide; ELISA: enzyme-linked immunosorbent assay; FBS: fetal bovine serum; GFAP: glial fibrillary acidic protein; IL1B/IL-1β: interleukin 1 beta; IL6/IL-6: interleukin 6; LPAR5: lysophosphatidic acid receptor 5; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; NOS2/iNOS: nitric oxide synthase 2, inducible; OGD: oxygen glucose deprivation; PAR: polymer of poly (ADP ribose); PARP: poly (ADP-ribose) polymerase family; PBS: phosphate-buffered saline; PLAT/tPA: plasminogen activator, tissue; PT: photothrombotic stroke; qPCR: quantitative polymerase chain reaction; Rap: rapamycin; RBFOX3/NeuN: RNA binding protein, fox-1 homolog (C. elegans) 3; SQSTM1: sequestosome 1; TNF/TNF-α: tumor necrosis factor.

The roles of post-translational modifications and coactivators of STAT6 signaling in tumor growth and progression

Signal transducers and activators of transcription 6 (STAT6) are highly expressed in various tumors and associated with tumorigenesis, immunosuppression, proliferation, metastasis and poor prognosis in human cancers. In response to IL-4/13, STAT6 is phosphorylated, dimerizes and triggers transcriptional regulation after recruitment of coactivators to transcriptosome, such as CBP/p300, SRC-1, PARP-14 and PSF. Post-translational modifications, including phosphorylation, ubiquitination, ADP-ribosylation and acetylation, have been explored for molecular mechanisms of STAT6 in tumor development and management. STAT6 has been developed as a specific biomarker for distinguishing and diagnosing tumor phenotypes, although it is observed to be frequently mutated in metastatic tumors. In this article, we focus mainly on the structural characteristics of STAT6 and its role in tumor growth and progression.

Genome-wide CRISPR synthetic lethality screen identifies a role for the ADP-ribosyltransferase PARP14 in DNA replication dynamics controlled by ATR

The DNA damage response is essential to maintain genomic stability, suppress replication stress, and protect against carcinogenesis. The ATR-CHK1 pathway is an essential component of this response, which regulates cell cycle progression in the face of replication stress. PARP14 is an ADP-ribosyltransferase with multiple roles in transcription, signaling, and DNA repair. To understand the biological functions of PARP14, we catalogued the genetic components that impact cellular viability upon loss of PARP14 by performing an unbiased, comprehensive, genome-wide CRISPR knockout genetic screen in PARP14-deficient cells. We uncovered the ATR-CHK1 pathway as essential for viability of PARP14-deficient cells, and identified regulation of DNA replication dynamics as an important mechanistic contributor to the synthetic lethality observed. Our work shows that PARP14 is an important modulator of the response to ATR-CHK1 pathway inhibitors.

Sequence homology between human PARP14 and the SARS-CoV-2 ADP ribose 1'-phosphatase

•There is amino acid sequence homology between the ADP-ribose binding sites of human PARP14 and SARS-CoV-2 ADRP. •This homology is even more pronounced in bat species. •The model proposed highlights the potential of the PARP axis to yield druggable targets for the treatment of COVID-19.

The Multifactorial Role of PARP-1 in Tumor Microenvironment

Poly(ADP-ribose) polymerases (PARPs), represent a family of 17 proteins implicated in a variety of cell functions; some of them possess the enzymatic ability to synthesize and attach poly (ADP-ribose) (also known as PAR) to different protein substrates by a post-translational modification; PARPs are key components in the cellular response to stress with consequences for different physiological and pathological events, especially during neoplasia. In recent years, using PARP inhibitors as antitumor agents has raised new challenges in understanding their role in tumor biology. Notably, the function of PARPs and PAR in the dynamic of tumor microenvironment is only starting to be understood. In this review, we summarized the conclusions arising from recent studies on the interaction between PARPs, PAR and key features of tumor microenvironment such as hypoxia, autophagy, tumor initiating cells, angiogenesis and cancer-associated immune response.

The impact of PARPs and ADP-ribosylation on inflammation and host-pathogen interactions

Poly-adenosine diphosphate-ribose polymerases (PARPs) promote ADP-ribosylation, a highly conserved, fundamental posttranslational modification (PTM). PARP catalytic domains transfer the ADP-ribose moiety from NAD⁺ to amino acid residues of target proteins, leading to mono- or poly-ADP-ribosylation (MARylation or PARylation). This PTM regulates various key biological and pathological processes. In this review, we focus on the roles of the PARP family members in inflammation and host-pathogen interactions. Here we give an overview the current understanding of the mechanisms by which PARPs promote or suppress proinflammatory activation of macrophages, and various roles PARPs play in virus infections. We also demonstrate how innovative technologies, such as proteomics and systems biology, help to advance this research field and describe unanswered questions.

Diverse therapeutic efficacies and more diverse mechanisms of nicotinamide

BACKGROUND

Nicotinamide (NAM) is a form of vitamin B3 that, when administered at near-gram doses, has been shown or suggested to be therapeutically effective against many diseases and conditions. The target conditions are incredibly diverse ranging from skin disorders such as bullous pemphigoid to schizophrenia and depression and even AIDS. Similar diversity is expected for the underlying mechanisms. In a large portion of the conditions, NAM conversion to nicotinamide adenine dinucleotide (NAD⁺) may be a major factor in its efficacy. The augmentation of cellular NAD⁺ level not only modulates mitochondrial production of ATP and superoxide, but also activates many enzymes. Activated sirtuin proteins, a family of NAD⁺-dependent deacetylases, play important roles in many of NAM's effects such as an increase in mitochondrial quality and cell viability countering neuronal damages and metabolic diseases. Meanwhile, certain observed effects are mediated by NAM itself. However, our understanding on the mechanisms of NAM's effects is limited to those involving certain key proteins and may even be inaccurate in some proposed cases.

AIM OF REVIEW

This review details the conditions that NAM has been shown to or is expected to effectively treat in humans and animals and evaluates the proposed underlying molecular mechanisms, with the intention of promoting wider, safe therapeutic application of NAM.

KEY SCIENTIFIC CONCEPTS OF REVIEW

NAM, by itself or through altering metabolic balance of NAD⁺ and tryptophan, modulates mitochondrial function and activities of many molecules and thereby positively affects cell viability and metabolic functions. And, NAM administration appears to be quite safe with limited possibility of side effects which are related to NAM's metabolites.