Inactive Parp2 causes Tp53-dependent lethal anemia by blocking replication-associated nick ligation in erythroblasts.

Poly (ADP-ribose) polymerase (PARP) 1 and 2 enzymatic inhibitors (PARPi) are promising cancer treatments. But recently, their use has been hindered by unexplained severe anemia and treatment-related leukemia. In addition to enzymatic inhibition, PARPi also trap PARP1 and 2 at DNA lesions. Here we report that, unlike Parp2-/- mice, which develop normally, mice expressing catalytically inactive Parp2 (E534A and Parp2EA/EA) succumb to Tp53- and Chk2-dependent erythropoietic failure in utero, mirroring Lig1-/- mice. While DNA damage mainly activates PARP1, we demonstrate that DNA replication activates PARP2 robustly. PARP2 is selectively recruited and activated by 5'-phosphorylated nicks (5'p-nicks), including those between Okazaki fragments, resolved by ligase 1 (Lig1) and Lig3. Inactive PARP2, but not its active form or absence, impedes Lig1- and Lig3-mediated ligation, causing dose-dependent replication fork collapse, which is detrimental to erythroblasts with ultra-fast forks. This PARylation-dependent structural function of PARP2 at 5'p-nicks explains the detrimental effects of PARP2 inactivation on erythropoiesis, shedding light on PARPi-induced anemia and the selection for TP53/CHK2 loss.

The Rate of NAD+ Breakdown Is Maintained Constant against Deletion or Overexpression of NAD+-Degrading Enzymes in Mammalian Cells.

Cellular NAD+ is continuously degraded and synthesized under resting conditions. In mammals, NAD+ synthesis is primarily initiated from nicotinamide (Nam) by Nam phosphoribosyltransferase, whereas poly(ADP-ribose) polymerase 1 (PARP1) and 2 (PARP2), sirtuin1 (SIRT1), CD38, and sterile alpha and TIR motif containing 1 (SARM1) are involved in NAD+ breakdown. Using flux analysis with 2H-labeled Nam, we found that when mammalian cells were cultured in the absence of Nam, cellular NAD+ levels were maintained and NAD+ breakdown was completely suppressed. In the presence of Nam, the rate of NAD+ breakdown (RB) did not significantly change upon PARP1, PARP2, SIRT1, or SARM1 deletion, whereas stable expression of CD38 did not increase RB. However, RB in PARP1-deleted cells was much higher compared with that in wild-type cells, in which PARP1 activity was blocked with a selective inhibitor. In contrast, RB in CD38-overexpressing cells in the presence of a specific CD38 inhibitor was much lower compared with that in control cells. The results indicate that PARP1 deletion upregulates the activity of other NADases, whereas CD38 expression downregulates the activity of endogenous NADases, including PARP1 and PARP2. The rate of cellular NAD+ breakdown and the resulting NAD+ concentration may be maintained at a constant level, despite changes in the NAD+-degrading enzyme expression, through the compensatory regulation of NADase activity.

Leveraging PARP-1/2 to Target Distant Metastasis.

Poly (ADP-Ribose) Polymerase (PARP) inhibitors have changed the outcomes and therapeutic strategy for several cancer types. As a targeted therapeutic mainly for patients with BRCA1/2 mutations, PARP inhibitors have commonly been exploited for their capacity to prevent DNA repair. In this review, we discuss the multifaceted roles of PARP-1 and PARP-2 beyond DNA repair, including the impact of PARP-1 on chemokine signalling, immune modulation, and transcriptional regulation of gene expression, particularly in the contexts of angiogenesis and epithelial-to-mesenchymal transition (EMT). We evaluate the pre-clinical role of PARP inhibitors, either as single-agent or combination therapies, to block the metastatic process. Efficacy of PARP inhibitors was demonstrated via DNA repair-dependent and independent mechanisms, including DNA damage, cell migration, invasion, initial colonization at the metastatic site, osteoclastogenesis, and micrometastasis formation. Finally, we summarize the recent clinical advancements of PARP inhibitors in the prevention and progression of distant metastases, with a particular focus on specific metastatic sites and PARP-1 selective inhibitors. Overall, PARP inhibitors have demonstrated great potential in inhibiting the metastatic process, pointing the way for greater use in early cancer settings.

CHD1L Regulates Cell Survival in Breast Cancer and Its Inhibition by OTI-611 Impedes the DNA Damage Response and Induces PARthanatos.

The Chromodomain helicase DNA-binding protein 1-like (CHD1L) is a nucleosome remodeling enzyme, which plays a key role in chromatin relaxation during the DNA damage response. Genome editing has shown that deletion of CHD1L sensitizes cells to PARPi, but the effect of its pharmacological inhibition has not been defined. Triple-negative breast cancer SUM149PT, HCC1937, and MDA-MB-231 cells were used to assess the mechanism of action of the CHD1Li OTI-611. Cytotoxicity as a single agent or in combination with standard-of-care treatments was assessed in tumor organoids. Immunofluorescence was used to assess the translocation of PAR and AIF to the cytoplasm or the nucleus and to study markers of DNA damage or apoptosis. Trapping of PARP1/2 or CHD1L onto chromatin was also assessed by in situ subcellular fractionation and immunofluorescence and validated by Western blot. We show that the inhibition of CHD1L's ATPase activity by OTI-611 is cytotoxic to triple-negative breast cancer tumor organoids and synergizes with PARPi and chemotherapy independently of the BRCA mutation status. The inhibition of the remodeling function blocks the phosphorylation of H2AX, traps CHD1L on chromatin, and leaves PAR chains on PARP1/2 open for hydrolysis. PAR hydrolysis traps PARP1/2 at DNA damage sites and mediates PAR translocation to the cytoplasm, release of AIF from the mitochondria, and induction of PARthanatos. The targeted inhibition of CHD1L's oncogenic function by OTI-611 signifies an innovative therapeutic strategy for breast cancer and other cancers. This approach capitalizes on CHD1L-mediated DNA repair and cell survival vulnerabilities, thereby creating synergy with standard-of-care therapies.

Evaluation of the efficacy of marine natural products against PARP-1/2 proteins in high-grade serous ovarian cancer: insights into MD and SMD simulations.

High-grade serous ovarian cancer (HGSOC) is the most malignant and ubiquitous phenotype of epithelial ovarian cancer. Originating in the fallopian tubes and rapidly spreading to the ovaries, this highly heterogeneous disease is a result of serous tubal intraepithelial carcinoma. The proteins known as poly(ADP-ribose) polymerase (PARP) aid in the development of HGSOC by repairing the cancer cells that proliferate and spread metastatically. By using molecular docking to screen 1100 marine natural products (MNPs) from different marine environments against PARP-1/2 proteins, prominent PARP inhibitors (PARPi) were identified. Four compounds, alisiaquinone A, alisiaquinone C, ascomindone D and (+)-zampanolide referred to as MNP-1, MNP-2, MNP-3 and MNP-4, respectively, were chosen based on their binding affinity towards PARP-1/2 proteins, and their bioavailability and drug-like qualities were accessed using ADMET analysis. To investigate the structural stability and dynamics of these complexes, molecular dynamics simulations were performed for 200 ns. These results were compared with the complexes of olaparib (OLA), a PARPi that has been approved by the FDA for the treatment of advanced ovarian cancer. We determined that MNP-4 exhibited stronger binding energies with PARP-1/2 proteins than OLA by using MM/PBSA calculations. Hotspot residues from PARP-1 (E883, M890, Y896, D899 and Y907) and PARP-2 (Y449, F450, A451, S457 and Y460) showed strong interactions with the compounds. To comprehend the unbinding mechanism of MNP-4 complexed with PARP-1/2, steered molecular dynamics (SMD) simulations were performed. We concluded from the free energy landscape (FEL) map that PARP-1/2 are well-stabilised when the compound MNP-4 is bound rather than being pulled away from its binding pockets. This finding provides significant evidence regarding PARPi, which could potentially be employed in the therapeutic treatment of HGSOC.Communicated by Ramaswamy H. Sarma.

The dynamics and regulation of PARP1 and PARP2 in response to DNA damage and during replication.

DNA strand breaks activate Poly(ADP-ribose) polymerase (PARP) 1 and 2, which use NAD+ as the substrate to covalently conjugate ADP-ribose on themselves and other proteins (e.g., Histone) to promote chromatin relaxation and recruit additional DNA repair factors. Enzymatic inhibitors of PARP1 and PARP2 (PARPi) are promising cancer therapy agents that selectively target BRCA1- or BRCA2- deficient cancers. As immediate early responders to DNA strand breaks with robust activities, PARP1 and PARP2 normally form transient foci (<10 minutes) at the micro-irradiation-induced DNA lesions. In addition to enzymatic inhibition, PARPi also extend the presence of PARP1 and PARP2 at DNA lesions, including at replication forks, where they may post a physical block for subsequent repair and DNA replication. The dynamic nature of PARP1 and PARP2 foci made live cell imaging a unique platform to detect subtle changes and the functional interaction among PARP1, PARP2, and their regulators. Recent imaging studies have provided new understandings of the biological consequence of PARP inhibition and uncovered functional interactions between PARP1 and PARP2 and new regulators (e.g., histone poly(ADP-ribosylation) factor). Here, we review recent advances in dissecting the temporal and spatial Regulation of PARP1 and PARP2 at DNA lesions and discuss their physiological implications on both cancer and normal cells.

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.

Regulatory apoptotic fragment of PARP1 complements catalytic fragment for PAR and DNA-dependent activity but inhibits DNA-induced catalytic stimulation of PARP2.

To maintain tissue homeostasis, cell proliferation is balanced by cell death. PARP1 is an important protein involved in both processes. Upon sensing DNA damage, PARP1 forms poly(ADP-ribose) (PAR) chains to recruit the repair proteins, ensuring genome integrity and faithful cell proliferation. In addition, PAR also regulates the activity of PARP1. Persistent DNA damage can signal the cell to progress toward programmed cell death, apoptosis. During apoptosis, proteolytic cleavage of PARP1 generates an N-terminal, ZnF1-2PARP1 (DNA binding or regulatory fragment), and C-terminal, PARP1ΔZnF1-2 (catalytic or PAR carrier fragment), which exhibits a basal activity. Regulation of the apoptotic fragments by PAR has not been studied. Here, we report that PAR inhibits the basal level activity of PARP1ΔZnF1-2, and ZnF1-2PARP1 interacts with PARP1ΔZnF1-2 to exhibit DNA-dependent stimulation and partially restores the PAR-dependent stimulation. Interestingly, along with the auto-modification domain of PARP1, the DNA-binding domains, ZnF1-2PARP1, also acts as an acceptor of PARylation; therefore, ZnF1-2PARP1 exhibits a reduced affinity for DNA upon PARylation. Furthermore, we show that ZnF1-2PARP1 shows trans-dominant inhibition of DNA-dependent stimulation of PARP2. Altogether, our study explores the regulation of the catalytic activity of PARP1ΔZnF1-2 and PARP2 by the regulatory apoptotic fragment of PARP1.

[The Role of the WGR Domain in the Functions of PARP1 and PARP2].

The PARP1 and PARP2 proteins are members of the poly(ADP-ribose) polymerase family involved in the regulation of DNA repair and replication, RNA processing, ribosome biogenesis, transcription, cell division, and cell death. PARP1 and PARP2 are promising targets for the development of anticancer drugs and can be used in the treatment of cardiovascular, neurodegenerative, and other disorders. The WGR domain has been shown to play a central role in the functioning of PARP1 and PARP2 proteins. This review considers the mechanisms of functioning of WGR domains in the PARP1 and PARP2 proteins, which have several similar and specialized properties. Understanding these processes is of great interest to fundamental science and can contribute to the development of more effective and selective inhibitors of PARP1 and PARP2.

Poly(ADP-Ribose) Polymerase-1 Lacking Enzymatic Activity Is Not Compatible with Mouse Development.

Poly(ADP-ribose) polymerase-1 (PARP1) binds DNA lesions to catalyse poly(ADP-ribosyl)ation (PARylation) using NAD+ as a substrate. PARP1 plays multiple roles in cellular activities, including DNA repair, transcription, cell death, and chromatin remodelling. However, whether these functions are governed by the enzymatic activity or scaffolding function of PARP1 remains elusive. In this study, we inactivated in mice the enzymatic activity of PARP1 by truncating its C-terminus that is essential for ART catalysis (PARP1ΔC/ΔC, designated as PARP1-ΔC). The mutation caused embryonic lethality between embryonic day E8.5 and E13.5, in stark contrast to PARP1 complete knockout (PARP1-/-) mice, which are viable. Embryonic stem (ES) cell lines can be derived from PARP1ΔC/ΔC blastocysts, and these mutant ES cells can differentiate into all three germ layers, yet, with a high degree of cystic structures, indicating defects in epithelial cells. Intriguingly, PARP1-ΔC protein is expressed at very low levels compared to its full-length counterpart, suggesting a selective advantage for cell survival. Noticeably, PARP2 is particularly elevated and permanently present at the chromatin in PARP1-ΔC cells, indicating an engagement of PARP2 by non-enzymatic PARP1 protein at the chromatin. Surprisingly, the introduction of PARP1-ΔC mutation in adult mice did not impair their viability; yet, these mutant mice are hypersensitive to alkylating agents, similar to PARP1-/- mutant mice. Our study demonstrates that the catalytically inactive mutant of PARP1 causes the developmental block, plausibly involving PARP2 trapping.

PARP2 downregulation in T cells ameliorates lipopolysaccharide-induced inflammation of the large intestine.

Introduction: T cell-dependent inflammatory response with the upregulation of helper 17 T cells (Th17) and the downregulation of regulatory T cells (Treg) accompanied by the increased production of tumor necrosis alpha (TNFa) is characteristic of inflammatory bowel diseases (IBD). Modulation of T cell response may alleviate the inflammation thus reduce intestinal damage. Poly(ADP-ribose) polymerase-2 (PARP2) plays role in the development, differentiation and reactivity of T cell subpopulations. Our aim was to investigate the potential beneficial effect of T cell-specific PARP2 downregulation in the lipopolysaccharide (LPS) induced inflammatory response of the cecum and the colon. Methods: Low-dose LPS was injected intraperitoneally to induce local inflammatory response, characterized by increased TNFa production, in control (CD4Cre; PARP2+/+) and T cell-specific conditional PARP2 knockout (CD4Cre; PARP2f/f) mice. TNFa, IL-1b, IL-17 levels were measured by ELISA, oxidative-nitrative stress was estimated by immunohistochemistry, while PARP1 activity, p38 MAPK and ERK phosphorylation, and NF-kB expression in large intestine tissue samples were examined by Western-blot. Systemic & local T cell subpopulation; Th17 and Treg alterations were also investigated using flowcytometry and immunohistochemistry. Results: In control animals, LPS induced intestinal inflammation with increased TNFa production, while no significant elevation of TNFa production was observed in T cell-specific PARP2 knockout animals. The absence of LPS-induced elevation in TNFa levels was accompanied by the absence of IL-1b elevation and the suppression of IL-17 production, showing markedly reduced inflammatory response. The increase in oxidative-nitrative stress and PARP1-activation was also absent in these tissues together with altered ERK and NF-kB activation. An increase in the number of the anti-inflammatory Treg cells in the intestinal mucosa was observed in these animals, together with the reduction of Treg count in the peripheral circulation. Discussion: Our results confirmed that T cell-specific PARP2 downregulation ameliorated LPS-induced colitis. The dampened TNFa production, decreased IL-17 production and the increased intestinal regulatory T cell number after LPS treatment may be also beneficial during inflammatory processes seen in IBD. By reducing oxidative-nitrative stress and PARP1 activation, T cell-specific PARP2 downregulation may also alleviate intestinal tissue damage.

PARP2 promotes inflammation in psoriasis by modulating estradiol biosynthesis in keratinocytes.

Poly(ADP-ribose) polymerase 2 (PARP2) alongside PARP1 are responsible for the bulk of cellular PARP activity, and they were first described as DNA repair factors. However, research in past decades implicated PARPs in biological functions as diverse as the regulation of cellular energetics, lipid homeostasis, cell death, and inflammation. PARP activation was described in Th2-mediated inflammatory processes, but studies focused on the role of PARP1, while we have little information on PARP2 in inflammatory regulation. In this study, we assessed the role of PARP2 in a Th17-mediated inflammatory skin condition, psoriasis. We found that PARP2 mRNA expression is increased in human psoriatic lesions. Therefore, we studied the functional consequence of decreased PARP2 expression in murine and cellular human models of psoriasis. We observed that the deletion of PARP2 attenuated the imiquimod-induced psoriasis-like dermatitis in mice. Silencing of PARP2 in human keratinocytes prevented their hyperproliferation, maintained their terminal differentiation, and reduced their production of inflammatory mediators after treatment with psoriasis-mimicking cytokines IL17A and TNFα. Underlying these observations, we found that aromatase was induced in the epidermis of PARP2 knock-out mice and in PARP2-deficient human keratinocytes, and the resulting higher estradiol production suppressed NF-κB activation, and hence, inflammation in keratinocytes. Steroidogenic alterations have previously been described in psoriasis, and we extend these observations by showing that aromatase expression is reduced in psoriatic lesions. Collectively, our data identify PARP2 as a modulator of estrogen biosynthesis by epidermal keratinocytes that may be relevant in Th17 type inflammation. KEY MESSAGES : PARP2 mRNA expression is increased in lesional skin of psoriasis patients. PARP2 deletion in mice attenuated IMQ-induced psoriasis-like dermatitis. NF-κB activation is suppressed in PARP2-deficient human keratinocytes. Higher estradiol in PARP2-deficient keratinocytes conveys anti-inflammatory effect.

[Poly(ADP-Ribose) Polymerases 1 and 2: Classical Functions and Interaction with New Histone Poly(ADP-Ribosyl)ation Factor HPF1].

Poly(ADP-ribose) (PAR) is a negatively charged polymer, linear or branched, that consists of ADP-ribose monomers. PAR is synthesized by poly(ADP-ribose)polymerase (PARP) enzymes, which are activated upon DNA damage and use nicotinamide adenine dinucleotide (NAD^(+)) as a substrate. The best-studied members of the PARP family, PARP1 and PARP2, are the most important nuclear proteins involved in many cell processes, including the regulation of DNA repair. PARP1 and PARP2 catalyze PAR synthesis and transfer to amino acid residues of target proteins, including autoPARylation. PARP1 and PARP2 are promising targets for chemotherapy in view of their key role in regulating DNA repair. A novel histone PARylation factor (HPF1) was recently discovered to modulate PARP1/2 activity by forming a transient joint active site with PARP1/2. Histones are modified at serine residues in the presence of HPF1. The general mechanism of the interaction between HPF1 and PARP1/2 is a subject of intense research now. The review considers the discovery and classical mechanism of PARylation in higher eukaryotes and the role of HPF1 in the process.

The HPF1-dependent histone PARylation catalyzed by PARP2 is specifically stimulated by an incised AP site-containing BER DNA intermediate.

Poly(ADP-ribose) polymerase 1 (PARP1) and PARP2 are DNA-dependent poly(ADP-ribose)transferases localized in nucleus. They have a significant homology in the C-terminal catalytic domain structure but differ in their N-terminal DNA-binding parts. The structural difference has an impact on the interaction of PARP1 and PARP2 with DNA and their DNA-dependent activation. Here, we compare the interaction of PARP1 and PARP2 with free 147 bp nucleosomal DNA and its nucleosome-associated variant (NCP) that contain in one strand a 1-nucleotide gap with 5'-dRP (imitating the intermediate of Base Excision Repair) or no specific damage. The affinity of PARP2 for the DNA strongly depends on the gap presence and to a lesser extent on the association with nucleosomes, while PARP1 interacts primarily with blunt ends of all DNAs and with a lower affinity with the single-strand break. The activities of PARP1 and PARP2 in the autoPARylation reaction and heteromodification of histones are distinctly stimulated by HPF1, depending on the gap presence in activating DNA. The most significant HPF1-induced stimulation of the histone modification in the presence of gapped NCP is a peculiar feature of PARP2. We propose a specific regulatory role of PARP2 in the process of DNA repair in the context of chromatin.

Revisiting PARP2 and PARP1 trapping through quantitative live-cell imaging.

Poly (ADP-ribose) polymerase-1 (PARP1) and 2 (PARP2) are two DNA damage-induced poly (ADP-ribose) (PAR) polymerases in cells and are the targets of PARP inhibitors used for cancer therapy. Strand breaks recruit and activate PARP1 and 2, which rapidly generate PAR from NAD+. PAR promotes the recruitment of other repair factors, relaxes chromatin, and has a role in DNA repair, transcription regulation, and RNA biology. Four PARP1/2 dual inhibitors are currently used to treat BRCA-deficient breast, ovarian, prostate, and pancreatic cancers. In addition to blocking the enzymatic activity of PARP1 and 2, clinical PARP inhibitors extend the appearance of PARP1 and PARP2 on chromatin after damage, termed trapping. Loss of PARP1 confers resistance to PARP inhibitors, suggesting an essential role of trapping in cancer therapy. Yet, whether the persistent PARP1 and 2 foci at the DNA damage sites are caused by the retention of the same molecules or by the continual exchange of different molecules remains unknown. Here, we discuss recent results from quantitative live-cell imaging studies focusing on PARP1 and PARP2's distinct DNA substrate specificities and modes of recruitment and trapping with implications for cancer therapy and on-target toxicities of PARP inhibitors.

Study of Interaction of the PARP Family DNA-Dependent Proteins with Nucleosomes Containing DNA Intermediates of the Initial Stages of BER Process.

Reaction of (ADP-ribosyl)ation catalyzed by DNA-dependent proteins of the poly(ADP-ribose)polymerase (PARP) family, PARP1, PARP2, and PARP3, comprises the cellular response to DNA damage. These proteins are involved in the base excision repair (BER) process. Despite the extensive research, it remains unknown how PARPs are involved in the regulation of the BER process and how the roles are distributed between the DNA-dependent members of the PARP family. Here, we investigated the interaction of the PARP's family DNA-dependent proteins with nucleosome core particles containing DNA intermediates of the initial stages of BER. To do that, the nucleosomes containing damage in the vicinity of one of the DNA duplex blunt ends were reconstituted based on the Widom's Clone 603 DNA sequence. Dissociation constants of the PARP complexes with nucleosomes bearing DNA contained uracil (Native), apurine/apyrimidine site (AP site), or a single-nucleotide gap with 5'-dRp fragment (Gap) were determined. It was shown that the affinity of the proteins for the nucleosomes increased in the row: PARP3<

Selective degradation of PARP2 by PROTACs via recruiting DCAF16 for triple-negative breast cancer.

Triple negative breast cancer (TNBC) is a complex and heterogeneous neoplasm, and till now no effective therapies are available. PARP inhibitors, which target DNA repair, are lethal to those cells that have impaired homologous recombination (HR) pathway. So, PARP inhibitors might exert promising results in the treatment of BRCA-mutated TNBC, but show compromised effect to those wild-type TNBC. Herein, we describe a novel PROTACs C8, which was obtained by conjugating PARP1/2 inhibitor Olaparib to KB02, can induce potent and specific degradation of PARP2 by recruiting DCAF16 E3 ligase for treatment of wild-type TNBC. Moreover, C8 exhibits therapeutic potential in TNBC cell lines MDA-MB-231 both in vitro and in vivo. These studies demonstrated that the DCAF16 E3 ligases can be used in PARP2 PROTACs design, and C8, as a novel PARP2 selective DCAF16 based PROTACs, might be a promising lead compound for the treatment of BRCA-wild-type TNBC.

Long non-coding RNA CCL2 promoted gastric cancer function via miR-128/ PARP2 signal pathway.

Amounts of studies have revealed long non-coding RNA (lncRNA) was related to the development of gastric cancer. Here, our results suggested the function and regulatory mechanism of CCL2 in gastric cancer. Quantitative polymerase-chain reaction (qPCR) was employed to inspect lncRNA CCL2 and miR-128 expression in normal gastric cell line (GES-1) and tumor cell lines (HGC-27 and MKN-45). The effects of CCL2 and miR-128 were measured via Luciferase reporter test. Western blot was used to check PARP2 protein expression. CCL2 expression and PARP2 protein levels were up-regulated, while miR-128 expression was obviously lower. Meanwhile, CCL2 down-regulating significantly repressed the proliferation, migration, and invasion by regulating miR-128. In addition, we proved miR-128 was a direct target of CCL2 through double luciferase assay and bioinformatics analysis. Moreover, miR-128 markedly inhibited the proliferation, migration, and invasion in gastric cancer. More importantly, miR-128 could reverse the effects of lncRNA CCL2 knocked down. PARP2-si obviously suppressed in gastric cancer proliferation, migration, and invasion. Meanwhile, miR-128 mimic and the knockout of CCL2 distinctly decreased PARP2 protein level. Additionally, luciferase report experiments certificated that PARP2 targeted miR-128, implying PARP2 directly interacted with miR-128 in gastric cancer. More interestingly, the downregulation of PARP could reverse the trend triggered by miR-128 inhibitor in gastric tumor. All over these results showed lncRNA CCL2 played importance of role in gastric tumor via miR-128/PARP2 axis signal pathway. LncRNA CCL2 accelerated gastric cancer progression by regulating miR-128/PARP2 signaling pathway, providing a novel possible strategy for the treatment of gastric cancer.

miR-149-PARP-2 Signaling Regulates E-cadherin and N-cadherin Expression in the Murine Model of Endometrium Receptivity.

Cadherins play an essential role in the attachment of the blastocyst to the endometrium, a process known as endometrial receptivity. Loss of E-cadherin expression is essential during the process, while the expression level of the other cadherin, N-cadherin, has been reported to be altered in cases of infertility. Both E-cadherin and N-cadherin can be regulated by members of the PARP family. Specifically, PARP-2, which is under the epigenetic control of miR-149, has been observed to promote E-cadherin expression in other human cells. We investigated the roles of E-cadherin and N-cadherin in endometrial receptivity using mouse models for normal endometrial receptivity, pseudopregnancy, and LPS-induced endometrial receptivity failure. E-cadherin and phosphorylated E-cadherin were predominantly expressed during pre-receptive stages as well as in the implantation site of the receptive stage, which were observed reduced during the later stages of implantation in both implantation and non-implantation regions, while N-cadherin was detected only at pre-receptive stages. E-cadherin and N-cadherin were also seen in the uterus during pseudopregnancy, showing a downregulation trend during receptive and post-receptive stages. LPS-induced failed endometrial receptivity showed upregulation of E-cadherin and downregulation of N-cadherin. The E-cadherin expression promoter, GSK-3, was lost and its suppressor, SLUG was upregulated during normal course of endometrial receptivity in mouse model, while GSK-3 was increased during LPS-induced failed embryo implantation. In an in vitro model of embryo implantation, E-cadherin expression is promoted by PARP-2 and regulated by miR-149 epigenetically in human endometrium epithelial cells. In conclusion, E-cadherin is predominantly expressed during pre-receptive stage and promoted by PARP-2, which is regulated by miR-149 in the endometrial epithelial cells.

Deficiency of PARP-1 and PARP-2 in the mouse uterus results in decidualization failure and pregnancy loss.

Miscarriage is a common complication of pregnancy for which there are few clinical interventions. Deficiency in endometrial stromal cell decidualization is considered a major contributing factor to pregnancy loss; however, our understanding of the underlying mechanisms of decidual deficiency are incomplete. ADP ribosylation by PARP-1 and PARP-2 has been linked to physiological processes essential to successful pregnancy outcomes. Here, we report that the catalytic inhibition or genetic ablation of PARP-1 and PARP-2 in the uterus lead to pregnancy loss in mice. Notably, the absence of PARP-1 and PARP-2 resulted in increased p53 signaling and an increased population of senescent decidual cells. Molecular and histological analysis revealed that embryo attachment and the removal of the luminal epithelium are not altered in uterine Parp1, Parp2 knockout mice, but subsequent decidualization failure results in pregnancy loss. These findings provide evidence for a previously unknown function of PARP-1 and PARP-2 in mediating decidualization for successful pregnancy establishment.