Role Of PARP-1 Research Articles

PARP-2 mediates cardiomyocyte aging and damage induced by doxorubicin through SIRT1 Inhibition.

Doxorubicin (DOX) is an anthracycline antibiotic used as an antitumor treatment. However, its clinical application is limited due to severe side effects such as cardiotoxicity. In recent years, numerous studies have demonstrated that cellular aging has become a therapeutic target for DOX-induced cardiomyopathy. However, the underlying mechanism and specific molecular targets of DOX-induced cardiomyocyte aging remain unclear. Poly (ADP-ribose) polymerase (PARP) is a family of protein post-translational modification enzymes in eukaryotic cells, including 18 members. PARP-1, the most well-studied member of this family, has become a potential molecular target for the prevention and treatment of various cardiovascular diseases, such as DOX cardiomyopathy and heart failure. PARP-1 and PARP-2 share 69% homology in the catalytic regions. However, they do not entirely overlap in function. The role of PARP-2 in cardiovascular diseases, especially in DOX-induced cardiomyocyte aging, is less studied. In this study, we found for the first time that down-regulation of PARP-2 can inhibit DOX-induced cellular aging in cardiomyocytes. On the contrary, overexpression of PARP-2 can aggravate DOX-induced cardiomyocyte aging and injury. Further research showed that PARP-2 inhibited the expression and activity of SIRT1, which in turn was involved in the development of DOX-induced cardiomyocyte aging and injury. Our findings provide a preliminary experimental basis for establishing PARP-2 as a new target for preventing and treating DOX cardiomyopathy and related drug development.

Heterochromatin-dependent Replication Stress: A Lesson from IDH1/2 Mutants.

Oncogenic point mutants of isocitrate dehydrogenases 1 and 2 (IDH2) generate 2-hydroxyglutarate (2HG), which inhibits lysine demethylases and increases heterochromatin. Tumor cells expressing IDH mutants are sensitive to poly(ADP) ribose polymerase (PARP) inhibitors, offering an opportunity to eliminate IDH-driven tumor cells in therapy. Expression of an oncogenic IDH1 mutant in cells leads to aberrant heterochromatin formation at DNA breaks and impairs DNA repair through homologous recombination (HR), providing a possible explanation for the PARP inhibitor sensitivity of IDH mutant cells. However, a recent study published in Molecular Cell shows that IDH mutant tumors do not display the genomic alterations associated with HR defects. Instead, IDH mutants induce heterochromatin-dependent DNA replication stress. Furthermore, PARP is activated by the replication stress induced by IDH mutants and required for suppressing the ensuing DNA damage, providing an alternative model to explain the susceptibility of IDH mutant cells to PARP inhibitors. This study presents a new example of oncogene-induced and heterochromatin-dependent replication stress, and a role of PARP in the response to the stress, extending the molecular basis for PARP-targeted therapy.

Dual function of HPF1 in the modulation of PARP1 and PARP2 activities

Poly(ADP-ribosyl)ation catalyzed by poly(ADP-ribose) polymerases (PARPs) is one of the immediate cellular responses to DNA damage. The histone PARylation factor 1 (HPF1) discovered recently to form a joint active site with PARP1 and PARP2 was shown to limit the PARylation activity of PARPs and stimulate their NAD+-hydrolase activity. Here we demonstrate that HPF1 can stimulate the DNA-dependent and DNA-independent autoPARylation of PARP1 and PARP2 as well as the heteroPARylation of histones in the complex with nucleosome. The stimulatory action is detected in a defined range of HPF1 and NAD+ concentrations at which no HPF1-dependent enhancement in the hydrolytic NAD+ consumption occurs. PARP2, comparing with PARP1, is more efficiently stimulated by HPF1 in the autoPARylation reaction and is more active in the heteroPARylation of histones than in the automodification, suggesting a specific role of PARP2 in the ADP-ribosylation-dependent modulation of chromatin structure. Possible role of the dual function of HPF1 in the maintaining PARP activity is discussed.

Role of PARP in TNBC: Mechanism of Inhibition, Clinical Applications, and Resistance.

Triple-negative breast cancer is a combative cancer type with a highly inflated histological grade that leads to poor theragnostic value. Gene, protein, and receptor-specific targets have shown effective clinical outcomes in patients with TNBC. Cells are frequently exposed to DNA-damaging agents. DNA damage is repaired by multiple pathways; accumulations of mutations occur due to damage to one or more pathways and lead to alterations in normal cellular mechanisms, which lead to development of tumors. Advances in target-specific cancer therapies have shown significant momentum; most treatment options cause off-target toxicity and side effects on healthy tissues. PARP (poly(ADP-ribose) polymerase) is a major protein and is involved in DNA repair pathways, base excision repair (BER) mechanisms, homologous recombination (HR), and nonhomologous end-joining (NEJ) deficiency-based repair mechanisms. DNA damage repair deficits cause an increased risk of tumor formation. Inhibitors of PARP favorably kill cancer cells in BRCA-mutations. For a few years, PARPi has shown promising activity as a chemotherapeutic agent in BRCA1- or BRCA2-associated breast cancers, and in combination with chemotherapy in triple-negative breast cancer. This review covers the current results of clinical trials testing and future directions for the field of PARP inhibitor development.

New Insights into the Significance of PARP-1 Activation: Flow Cytometric Detection of Poly(ADP-Ribose) as a Marker of Bovine Intramammary Infection.

Bovine intramammary infections are common diseases affecting dairy cattle worldwide and represent a major focus of veterinary research due to financial losses and food safety concerns. The identification of new biomarkers of intramammary infection, useful for monitoring the health of dairy cows and wellness verification, represents a key advancement having potential beneficial effects on public health. In vitro experiments using bovine peripheral blood mononuclear cells (PBMC), stimulated with the bacterial endotoxin lipopolysaccharide (LPS) enabled a flow cytometric assay in order to evaluate in vivo poly-ADP-ribose (PAR) levels. Results showed a significant increase of PAR after 1 h of treatment, which is consistent with the involvement of PARP activity in the inflammatory response. This study investigated PARP-1 activation in leukocyte subpopulations from bovine milk samples during udder infection. A flow cytometric assay was, therefore, performed to evaluate the PAR content in milk leukocyte subsets of cows with and without intramammary infection (IMI). Results showed that milk lymphocytes and macrophages isolated from cows with IMI had a significant increase of PAR content compared to uninfected samples. These results suggest mastitis as a new model for the study of the role of PARP in zoonotic inflammatory diseases, opening a new perspective to the “One Health” approach.

The multifaceted role of PARP1 in RNA biogenesis.

Poly(ADP‐ribose) polymerases (PARPs) are abundant nuclear proteins that synthesize ADP ribose polymers (pADPr) and catalyze the addition of (p)ADPr to target biomolecules. PARP1, the most abundant and well‐studied PARP, is a multifunctional enzyme that participates in numerous critical cellular processes. A considerable amount of PARP research has focused on PARP1's role in DNA damage. However, an increasing body of evidence outlines more routine roles for PARP and PARylation in nearly every step of RNA biogenesis and metabolism. PARP1's involvement in these RNA processes is pleiotropic and has been ascribed to PARP1's unique flexible domain structures. PARP1 domains are modular self‐arranged enabling it to recognize structurally diverse substrates and to act simultaneously through multiple discrete mechanisms. These mechanisms include direct PARP1‐protein binding, PARP1‐nucleic acid binding, covalent PARylation of target molecules, covalent autoPARylation, and induction of noncovalent interactions with PAR molecules. A combination of these mechanisms has been implicated in PARP1's context‐specific regulation of RNA biogenesis and metabolism. We examine the mechanisms of PARP1 regulation in transcription initiation, elongation and termination, co‐transcriptional splicing, RNA export, and post‐transcriptional RNA processing. Finally, we consider promising new investigative avenues for PARP1 involvement in these processes with an emphasis on PARP1 regulation of subcellular condensates.This article is categorized under:RNA Processing > Splicing Regulation/Alternative Splicing

Abstract 2918: Molecular analysis of the mechanism of action of AsiDNATM brings new clues on DNA damage response regulation

Abstract Purpose: Our laboratory succeeded at developing an original DNA repair inhibitor, called AsiDNATM, developed and tested in clinic by Onxeo. AsiDNATM is a small modified double-stranded DNA molecule vectorised by a covalently bound cholesterol. It acts by inhibiting DNA repair and sensitizes tumors to genotoxic treatments. Here we investigate the different steps involved in its activity. Experimental design: SK28, MRC-5 and MDA-MB-231 cells were treated by AsiDNATM. Cellular uptake of AsiDNATM was monitored by FACS and electron microscopy. AsiDNATM interacting proteins were identified by mass spectrometry in cell extracts pooled down with AsiDNA. Kinetics of activation of the two main targeted enzyme, DNA-PK and PARP, were monitored by measuring phosphorylation of H2AX and formation of poly-adenyl-ribose polymers (PAR) and NAD consumption. Inhibition of DNA repair enzymes recruitment at damage site (53BP1, XRCC4, BRCA1, Rad51 and NBS1) was analyzed by confocal microscopy. DNA damage were induced at different times after AsiDNATM addition. The role of PARP, DNA-PK and ATM enzymes in the recruitment inhibition was tested using specific inhibitors or deficient cells. DNA repair activity was analyzed by alcalin comet assay and survival curves were established. Transcriptomes were monitored 24h after AsiDNATMtreatment. Results: AsiDNATM enters the cells via cholesterol route using LDL receptors. It binds DNA-PK and PARP and triggers their activation for more than 24h. The levels of DNA-PK and PARP activation as well as NAD consumption were always higher than those induced by a 10 Gy irradiation. Survival rate to AsiDNATM alone was between 90% and 70%. No significant effect was observed on cell cycle or proliferation. Pretreatment of tumor cells with AsiDNATM inhibits DNA repair and increase cell death induced by irradiation. The earliest event observed after irradiation was a transitory phosphorylation of ATM(ser1981) disappearing after 2h. It was followed by the inhibition of 53BP1and XRCC4 recruitment in a PARP dependent manner. Then, concomitantly with γ-H2AX and PAR increase, recruitment of BRCA1 and RAD51 was inhibited in cells with high level of DNA-PK activation. This inhibition was dependent of DNA-PK and not of PARP or ATM. Transcriptome analysis showed large change in the expression of genes involved in metabolism. Conclusion: AsiDNATM inhibits NHEJ and HR double-strand break DNA repair by preventing the recruitment of key enzymes at break sites. The inhibition of NHEJ proteins recruitment is the earliest event and requires PARP activity. The inhibition of HR proteins appears lately and is dependent upon DNA-PK activation. PARP activation induces metabolism change that might participate to the antitumoral activity of AsiDNATM. These results highlight the unique mechanism of action of AsiDNATM through the activation of two complementary key enzymes involved in DNA damage response. Citation Format: Nathalie Berthault, Kozlac Maria, Sergey Alekseev, Pierre-Marie Girard, Marie Dutreix. Molecular analysis of the mechanism of action of AsiDNATM brings new clues on DNA damage response regulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2918.

PS984 CANNABINOIDS EXERT A POTENT ANTI‐LEUKEMIC EFFECT AFFECTING SIGNALING PATHWAYS INVOLVED IN TUMOR CELL METABOLISM

Background:Cannabinoids exert their activity upon interaction with cannabinoid receptors: CB1, mostly expressed in the central nervous system and CB2, mainly found in hematopoietic cells. We have described the effect of cannabinoid derivatives in multiple myeloma (Barbado et al, 2018). In this work, we present evidence that cannabinoids acts as a cytotoxic agent against acute myeloid leukemia (AML) blasts without affecting normal hematopoietic cells.Aims:Our main goal is to determine the mechanism of action by which cannabinoids exert their antileukemic effect.Methods:Cell viability was determined by MTT assay and flow cytometry analysis of Annexin V/7‐AAD using 6 AML cell lines, primary hematopoietic stem cells (HSC), lymphocytes from healthy donors and 23 AML patients. mRNA expression profile of HL60 AML cells treated with WIN‐55 vs untreated cells was studied by Clariom S Assays Human (Affimetrix) and Transcriptome Analysis Console (TAC) Software (Thermo Fisher). Western blot and immunoflurescence assays were performed to determine protein expression upon WIN‐55 exposure, including endoplasmic reticulum stress protein. TMRE and MitoSOXTM Red was used to determine mitochondrial damage. The contribution of compounds (glycine, serine, N‐Acetyl‐cysteine, 2‐mercaptoethanol, oxaloacetic acid and methyl pyruvate) involved in key metabolic processes affected upon WIN‐55 exposure were also assessed. Glycolytic flux was assessed by ECAR in a XF24 flux analyzer (Seahorse Biosciences). NAD/NADH and ADP/ATP ratio and Hexokinase activity was also measured. Ceramide and other sphingolipids were quantitated by HPLC‐MS/MS and immunohistochemistry. HL60‐xenotransplant NSG mouse model were established, bone marrow (BM) infiltration confirmed by BM aspirate and subsequent flow cytometry, and WIN‐55 or citarabine treatments was administered. The effect of WIN‐55 on normal hematopoiesis of healthy BALB‐C mice was assessed by flow cytometry and hemogram.Results:We confirmed a potent cytotoxic effect of WIN‐55 on AML cell lines while normal HSC remained unaffected. mRNA expression profile using showed that the pathways mainly affected upon WIN‐55 exposure were unfolded protein response (UPR) and XBP1 activates chaperon genes, PI3K‐Akt‐mTOR, VEGFA‐VEGFR2 and Adipogenesis Signaling Pathway. Using WB assays we confirmed that WIN‐55 triggered caspases activation and we detected ceramide accumulation in AML cells. Also studies on p‐PERK, p‐IRE1 and CHOP confirmed an increased endoplasmic reticulum stress upon exposure to cannabinoids. Pathways involved in cell proliferation/survival including p‐JNK, p‐Erk1/2, p‐p38‐MAPK and p‐AKT were affected. An early mitochondrial damage was also observed in leukemic cells upon exposure to the drug. Ceramide synthesis inhibition prevented less than 10% of the WIN‐55 induced‐apoptosis. By contrast, the proapoptotic effect of cannabinoids on AML cells was abolished upon co‐culture with either CB2 receptor antagonists, pancaspase inhibitors, olaparib (a PARP inhibitor) or glycine. Cannabinoids did not affect the viability of HSC from healthy donors neither in vitro not in vivo, resulting in a lack of hematopoietic toxicity in healthy treated mice. Finally, WIN‐55 significantly prolonged the survival of AML xenografted mice.Summary/Conclusion:Cannabinoids have a potent and selective anti‐leukemic effect affecting several signaling and metabolic pathways. The role of PARP is essential in this apoptotic effect, which is mediated by CB2 receptor. Differences in the metabolic requirements between normal and leukemic cells account for this differential effect.

MicroRNA‐203 regulates cell junction and adhesion proteins by modulating Zeb1/Vimentin axis in breast cancer cells after PARP1 inhibition.

PARP inhibitors are currently in trend to treat various type of cancers and they have shown promising results in homologous recombination deficient breast and ovarian cancers like those bearing BRCA1/2 mutations. There are many reports describing about the failure of PARP inhibitors due to resistance or unknown factors in clinical trials. It is crucial to look into in‐depth molecular mechanisms behind the role of PARP in cancer pathogenesis and long term effect of PARP inhibition. MicroRNAs (miRNAs) are small non‐coding RNAs, acting as post‐transcriptional regulators of gene expression and known to regulate variety of cellular processes, including the DNA damage response and regulation of cell junction and adhesion proteins. However, little is known about miRNAs mediated regulation of sensitivity to PARP inhibitors and its pathological significance in context to regulation of cell junction and adhesion proteins. Aberrant miRNA regulation of junction proteins is one of the leading causes of cancer pathogenesis. Keeping these views in consideration, we aimed to identify novel miRNAs involved in the regulation of cell junction and adhesion proteins in breast cancer malignancy after PARP inhibition. To investigate this, we performed miRNA microarray analysis of PARP inhibitor treated MDA‐MB‐231 cells and found upregulation of tumor suppressor miR‐203 after PARP inhibition. PARP1 inhibition led to reduced expression of vimentin and Zeb1 while ZO‐1, E‐cadherin and RhoGDI were upregulated in breast cancer cells. To confirm the whether PARP inhibitory effects were mediated by miR‐203, cells were transfected with miR‐203 mimic and anti‐miR. We observed that miR‐203 mimic resulted in inhibition of junction proteins Zeb1 and vimentin, coinciding with PARP inhibition. We also found that PARP inhibition caused reduced cell growth and proliferation of breast cancer cells which correlated with the overexpression of miR‐203. Our findings indicates that upregulation of miR‐203 due to PARP inhibition is involved in regulating cell junction proteins vimentin and zeb1 as well as cytosketelal RhoGTPase and thus regulating cell migration, invasion and proliferation. Taken together, these observations raise the possibility that these miRNAs could be used as biomarkers to identify patients that may benefit from treatment with PARP inhibitors.Support or Funding InformationJR acknowledge the support from Department of Biotechnology (DBT) for DBT Bio‐CARe fellowship. NS acknowledges the support by the senior research fellowship from the Indian Council of Medical Research (ICMR). This work was supported by the grants from Department of Biotechnology (GAP0187) to DP Mishra.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

PARP1 and PARP2 stabilise replication forks at base excision repair intermediates through Fbh1-dependent Rad51 regulation

PARP1 regulates the repair of DNA single-strand breaks generated directly, or during base excision repair (BER). However, the role of PARP2 in these and other repair mechanisms is unknown. Here, we report a requirement for PARP2 in stabilising replication forks that encounter BER intermediates through Fbh1-dependent regulation of Rad51. Whereas PARP2 is dispensable for tolerance of cells to SSBs or homologous recombination dysfunction, it is redundant with PARP1 in BER. Therefore, combined disruption of PARP1 and PARP2 leads to defective BER, resulting in elevated levels of replication-associated DNA damage owing to an inability to stabilise Rad51 at damaged replication forks and prevent uncontrolled DNA resection. Together, our results demonstrate how PARP1 and PARP2 regulate two independent, but intrinsically linked aspects of DNA base damage tolerance by promoting BER directly, and by stabilising replication forks that encounter BER intermediates.

Transcriptome-wide identification of the RNA-binding landscape of the chromatin-associated protein PARP1 reveals functions in RNA biogenesis

Recent studies implicate Poly (ADP-ribose) polymerase 1 (PARP1) in alternative splicing regulation, and PARP1 may be an RNA-binding protein. However, detailed knowledge of RNA targets and the RNA-binding region for PARP1 are unknown. Here we report the first global study of PARP1–RNA interactions using PAR–CLIP in HeLa cells. We identified a largely overlapping set of 22 142 PARP1–RNA-binding peaks mapping to mRNAs, with 20 484 sites located in intronic regions. PARP1 preferentially bound RNA containing GC-rich sequences. Using a Bayesian model, we determined positional effects of PARP1 on regulated exon-skipping events: PARP1 binding upstream and downstream of the skipped exons generally promotes exon inclusion, whereas binding within the exon of interest and intronic regions closer to the skipped exon promotes exon skipping. Using truncation mutants, we show that removal of the Zn1Zn2 domain switches PARP1 from a DNA binder to an RNA binder. This study represents a first step into understanding the role of PARP1–RNA interaction. Continued identification and characterization of the functional interplay between PARPs and RNA may provide important insights into the role of PARPs in RNA regulation.

An analysis of the gene interaction networks identifying the role of PARP1 in metastasis of non-small cell lung cancer.

Background and ObjectiveThough there were many researches about the effects of cancer cells on non-small cell lung cancer (NSCLC) currently, it has been rarely reported completed oncogene and its mechanism in tumors by far. Here, we used biological methods with known oncogene of NSCLC to find new oncogene and explore its functionary mechanism in NSCLC.MethodsThe study firstly built NSCLC genetic interaction network based on bioinformatics methods and then combined shortest path algorithm with significance test to confirmed core genes that were closely involved with given genes; real-time qPCR was conducted to detect expression levels between patients with NSCLC and normal people; additionally, detection of PARP1's role in migration and invasion was performed by trans-well assays and wound-healing.ResultsThrough gene interaction network, it was found that, core genes like PARP1, EGFR and ALK had a direct interaction. TCGA database showed that PARP1 presented strong expression in NSCLC and the expression level of metastatic NSCLC was significantly higher than that of non-metastatic NSCLC. Cell migration of NSCLC in accordance to the scratch test was suppressed by PARP1 silence but stimulated noticeably by PARP1 overexpression. According to Kaplan-meier survival curve, the higher PARP1 expression, the poorer patient survival rate and prognosis. Thus, PARP1 expression had a negative correction with patient survival rate and prognosis.ConclusionNew oncogene PARP1 was found from known NSCLC oncogene in terms of gene interaction network, demonstrating PARP1's impact on NSCLC cell migration.

Poly(ADP-ribose) polymerases regulate cell division and development in Arabidopsis roots.

Root organogenesis involves cell division, differentiation and expansion. The molecular mechanisms regulating root development are not fully understood. In this study, we identified poly(adenosine diphosphate (ADP)-ribose) polymerases (PARPs) as new players in root development. PARP catalyzes poly(ADP-ribosyl)ation of proteins by repeatedly adding ADP-ribose units onto proteins using nicotinamide adenine dinucleotide (NAD+ ) as the donor. We found that inhibition of PARP activities by 3-aminobenzomide (3-AB) increased the growth rates of both primary and lateral roots, leading to a more developed root system. The double mutant of Arabidopsis PARPs, parp1parp2, showed more rapid primary and lateral root growth. Cyclin genes regulating G1-to-S and G2-to-M transition were up-regulated upon treatment by 3-AB. The proportion of 2C cells increased while cells with higher DNA ploidy declined in the roots of treated plants, resulting in an enlarged root meristematic zone. The expression level of PARP2 was very low in the meristematic zone but high in the maturation zone, consistent with a role of PARP in inhibiting mitosis and promoting cell differentiation. Our results suggest that PARPs play an important role in root development by negatively regulating root cell division.

The clinically used PARP inhibitor olaparib improves organ function, suppresses inflammatory responses and accelerates wound healing in a murine model of third-degree burn injury.

The PARP inhibitor olaparib has recently been approved for human use for the therapy of cancer. Considering the role of PARP in critical illness, we tested the effect of olaparib in a murine model of burn injury, in order to begin exploring the feasibility of repurposing olaparib for the therapy of burn patients. Mice were subjected to scald burn injury and randomized into vehicle or olaparib (10mg·kg-1 ·day-1 i.p.) groups. Outcome variables included indices of organ injury, clinical chemistry parameters, plasma levels of inflammatory mediators (at 24h, 7 and 21days) and burn wound size (at 21days). Olaparib reduced myeloperoxidase levels in heart and lung homogenates and reduced malondialdehyde levels in all tissues 24h post-burn. Olaparib also reduced circulating alkaline aminotransferase, amylase and blood urea nitrogen and creatinine levels, indicative of protection against hepatic, pancreatic and renal dysfunction. Pro-inflammatory mediator (TNF-α, IL-1β, IFN-γ, GCSF, GM-CSF, eotaxin, KC, MIP-1-α and IL-3, 6 and 12) levels as well as the levels of several mediators that are generally considered anti-inflammatory (IL-4, 10 and 13) were reduced by olaparib. Plasma troponin-I levels (an indicator of skeletal muscle damage) was also attenuated by olaparib. Finally, olaparib stimulated wound healing. The clinically approved PARP inhibitor olaparib improves organ function, suppresses inflammatory responses and accelerates wound healing in murine burn injury. The data raise the potential utility of olaparib for severe burn injury. This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

P.5.c.014 - Mechanism of amyloid beta peptides and alfa synuclein cytotoxicity. The role of PARPs and sirtuins. Implications in Alzheimer’s disease

P.5.c.014 - Mechanism of amyloid beta peptides and alfa synuclein cytotoxicity. The role of PARPs and sirtuins. Implications in Alzheimer’s disease

Poly(ADP-Ribose) Polymerases in Aging - Friend or Foe?

Poly(ADP-ribose) polymerases were originally described as DNA repair enzymes. PARP-1, PARP-2 and PARP-3 can be activated by DNA damage and the resulting activation of these enzymes that facilitate DNA repair, seems to be a prerequisite of successful aging. PARP activation helps to maintain genomic integrity through supporting DNA repair systems; however, in parallel these enzymes limit metabolic fitness and make the organism more prone for metabolic diseases. In addition, several other pathways (e.g., proteostasis, nutrient sensing, stem cell proliferation or cellular communication) all contributing to aging, were shown to be PARP mediated. In this review we aim to summarize our current knowledge on the role of PARPs in aging.

HG-05DIFFERENTIAL EXPRESSION OF PARP1/2 AS A BIOMARKER OF DIPG MALIGNANT PROGRESSION: RELATIONSHIP TO TGF-β/BMP SIGNALING AND EZH2 GLOBAL METHYLATION

HG-05. DIFFERENTIAL EXPRESSION OF PARP1/2 AS A BIOMARKER OF DIPG MALIGNANT PROGRESSION: RELATIONSHIP TO TGF-b/BMP SIGNALING AND EZH2 GLOBAL METHYLATION Uday Bhanu Maachani1, Uma Shankavaram2, Melanie Schweitzer1, Yue Linda Wu1, Kevin Camphausen2, and Mark Souweidane1; Weill Cornell Medicine, New York, NY, USA; National Cancer Institute-NIH, Bethesda, MD, USA Diffuse intrinsic pontine gliomas (DIPG) which occur in the brain stem are the most malignant inoperable and hard to treat brain tumors in children. Many reports indicate DIPG as being unique in terms of the molecular process that drives their malignancy. Recently, Poly (ADP-ribose) polymerase 1 & 2 (PARP1/2) have gained much attention as potential promising therapeutic targets for the treatment of solid tumors including DIPG. In this study, we defined molecular landscape of DIPG tumor samples by using a large public retrospective gene expression data set (n 1⁄4 53) and performed detailed bio-informatics analysis to generate hypotheses regarding potential mechanisms associated with PARP expression. Different associations between PARP and TGF-b/BMP, EZH2 signaling pathway genes were observed (low vs high). We found a negative co-relation between PARP expression and TGBRII, BMP2 and BMP2K genes, with much stronger correlation in patients with H3F3A mutation (present in 65-75% of tumors) suggesting negative role of PARP on TGF-b/BMP signaling. We noticed significant positive correlation of PARP with EZH2 and UHRF1BP1 genes knownto regulate global methylation and their increased expression is recognized to inhibit genes responsible for suppressing tumor development. Further patients with highPARPexpression along with high EZH2 and lowBMP signaling were correlated with poor prognosis to survival. In conclusion, these results reveal potential biological role of PARP in regulating TGF-b/BMP signaling and global methylation driving DIPG tumorigenesis. Moreover, these findings delineate pathways of susceptibility that could be disrupted to confer strong sensitivity to PARP inhibitors. Neuro-Oncology 18:iii48–iii77, 2016. doi:10.1093/neuonc/now073.4 #The Author(s) 2016. Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Poly(ADP-Ribose) Polymerase in Cervical Cancer Pathogenesis: Mechanism and Potential Role for PARP Inhibitors

Treatment options for disease recurrence of women treated for locally advanced and advanced cervical cancer are very limited-largely palliative chemotherapy. The low efficacy of the currently available drugs raises the need for new targeted agents. Poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitors (PARPi) have emerged as a promising class of chemotherapeutic agents in cancers associated with defects in DNA repair. Their therapeutic potential in cervical cancer is currently being evaluated in 3 ongoing clinical trials. Here we review the available information regarding all the aspects of PARP in cervical intraepithelial neoplasia and invasive cervical cancer, from expression and the mechanism of action to the role of the polymorphisms in the pathogenesis of the disease, as well as the potential of the inhibitors. We finally propose a new unifying theory regarding the role of PARPs in the development of cervical carcinomas.

PARP-1 inhibition modulates gene expression of mitochondria sirtuins and APP secretases: The role of PARP and sirts interaction in amyloid beta toxicity

PARP-1 inhibition modulates gene expression of mitochondria sirtuins and APP secretases: The role of PARP and sirts interaction in amyloid beta toxicity

Interaction of PARP-2 with AP site containing DNA.

In eukaryotes the stability of genome is provided by functioning of DNA repair systems. One of the main DNA repair pathways in eukaryotes is the base excision repair (BER). This system requires precise regulation for correct functioning. Two members of the PARP family - PARP-1 and PARP-2, which can be activated by DNA damage - are widely considered as regulators of DNA repair processes, including BER. In contrast to PARP-1, the role of PARP-2 in BER has not been extensively studied yet. Since AP site is one of the most frequent type of DNA damage and a key intermediate of BER at the stage preceding formation of DNA breaks, in this paper we focused on the characterization of PARP-2 interaction with AP site-containing DNAs. We demonstrated that PARP-2, like PARP-1, can interact with the intact AP site via Schiff base formation, in spite of crucial difference in the structure of the DNA binding domains of these PARPs. By cross-linking of PARPs to AP DNA, we determined that the N-terminal domains of both PARPs are involved in formation of cross-links with AP DNA. We have also confirmed that DNA binding by PARP-2, in contrast to PARP-1, is not modulated by autoPARylation. PARP-2, like PARP-1, can inhibit the activity of APE1 by binding to AP site, but, in contrast to PARP-1, this inhibitory influence is hardly regulated by PAR synthesis. At the same time, 5'-dRP lyase activity of both PARPs is comparable, although being much weaker than that of Pol β, which is considered as the main 5'-dRP lyase of the BER process.