bims-numges 2021-01-10 papers

bims-numges

Biomed News

on Nucleotide metabolism and genome stability

Issue of 2021–01–10
29 papers selected by
Sean Rudd, Karolinska Institutet

CARM1 regulates replication fork speed and stress response by stimulating PARP1.
Targeting translesion synthesis (TLS) to expose replication gaps, a unique cancer vulnerability.
Ligation of newly replicated DNA controls the timing of DNA mismatch repair.
Checkpoint inhibition of origin firing prevents inappropriate replication outside of S-phase.
A Mitochondrial Orthologue of the dNTP Triphosphohydrolase SAMHD1 Is Essential and Controls Pyrimidine Homeostasis in Trypanosoma brucei.
MRE11-RAD50-NBS1 Complex Is Sufficient to Promote Transcription by RNA Polymerase II at Double-Strand Breaks by Melting DNA Ends.
SUMOylation mediates CtIP's functions in DNA end resection and replication fork protection.
Cyclin A2 localises in the cytoplasm at the S/G2 transition to activate PLK1.
The toxic side of one-carbon metabolism and epigenetics.
Poly(ADP-ribosyl)ation temporally confines SUMO-dependent ataxin-3 recruitment to control DNA double-strand break repair.
ATR Kinase Is a Crucial Player Mediating the DNA Damage Response in Trypanosoma brucei.
Base and Nucleotide Excision Repair Pathways in DNA Plasmids Harboring Oxidatively Generated Guanine Lesions.
DNA-protein crosslink proteases in genome stability.
Discovery of a novel inhibitor of human purine nucleoside phosphorylase by a simple hydrophilic interaction liquid chromatography (HILIC-UV) enzymatic assay.
Enhancing the activity of platinum-based drugs by improved inhibitors of ERCC1-XPF-mediated DNA repair.
O6-methylguanine-DNA methyltransferase modulates cisplatin-induced DNA double-strand breaks by targeting the homologous recombination pathway in nasopharyngeal carcinoma.
Resveratrol induces H3 and H4K16 deacetylation and H2A.X phosphorylation in Toxoplasma gondii.
The active DNA-PK holoenzyme occupies a tensed state in a staggered synaptic complex.
FEN1 inhibitor synergizes with low-dose camptothecin to induce increased cell killing via the mitochondria mediated apoptotic pathway.
Targeting DNA-PK overcomes acquired resistance to third-generation EGFR-TKI osimertinib in non-small-cell lung cancer.
A spatial and functional interaction of a heterotetramer Survivin-DNA-PKcs complex in DNA damage response.
A large intermediate domain of vertebrate REV3 protein is dispensable for ultraviolet-induced translesion replication.
The ATM and ATR kinases regulate centrosome clustering and tumor recurrence by targeting KIFC1 phosphorylation.
Targeting phosphoglycerate dehydrogenase in multiple myeloma.
Catalytically inactive Cas9 impairs DNA replication fork progression to induce focal genomic instability.
Regulation of purine metabolism connects KCTD13 to a metabolic disorder with autistic features.
P2Y Receptors for Extracellular Nucleotides: Contributions to Cancer Progression and Therapeutic Implications.
Evidence for a Cross-Talk Between Cytosolic 5'-Nucleotidases and AMP-Activated Protein Kinase.
MTT Test and Time-lapse Microscopy to Evaluate the Antitumor Potential of Nucleoside Analogues.

Mol Cell. 2020 Dec 30. pii: S1097-2765(20)30902-3. [Epub ahead of print]

CARM1 regulates replication fork speed and stress response by stimulating PARP1.

Marie-Michelle Genois, Jean-Philippe Gagné, Takaaki Yasuhara, Jessica Jackson, Sneha Saxena, Marie-France Langelier, Ivan Ahel, Mark T Bedford, John M Pascal, Alessandro Vindigni, Guy G Poirier, Lee Zou.

  DNA replication forks use multiple mechanisms to deal with replication stress, but how the choice of mechanisms is made is still poorly understood. Here, we show that CARM1 associates with replication forks and reduces fork speed independently of its methyltransferase activity. The speeding of replication forks in CARM1-deficient cells requires RECQ1, which resolves reversed forks, and RAD18, which promotes translesion synthesis. Loss of CARM1 reduces fork reversal and increases single-stranded DNA (ssDNA) gaps but allows cells to tolerate higher replication stress. Mechanistically, CARM1 interacts with PARP1 and promotes PARylation at replication forks. In vitro, CARM1 stimulates PARP1 activity by enhancing its DNA binding and acts jointly with HPF1 to activate PARP1. Thus, by stimulating PARP1, CARM1 slows replication forks and promotes the use of fork reversal in the stress response, revealing that CARM1 and PARP1 function as a regulatory module at forks to control fork speed and the choice of stress response mechanisms.

Keywords:  CARM1; PARP1; PARylation; PrimPol; RECQ1; fork reversal; fork speed; replication fork; replication stress; translesion synthesis

DOI:  https://doi.org/10.1016/j.molcel.2020.12.010
Expert Opin Ther Targets. 2021 Jan 08. 1-10

Targeting translesion synthesis (TLS) to expose replication gaps, a unique cancer vulnerability.

Sumeet Nayak, Jennifer A Calvo, Sharon B Cantor.

  Introduction: Translesion synthesis (TLS) is a DNA damage tolerance (DDT) mechanism that employs error-prone polymerases to bypass replication blocking DNA lesions, contributing to a gain in mutagenesis and chemo-resistance. However, recent findings illustrate an emerging role for TLS in replication gap suppression (RGS), distinct from its role in post-replication gap filling. Here, TLS protects cells from replication stress (RS)-induced toxic single-stranded DNA (ssDNA) gaps that accumulate in the wake of active replication. Intriguingly, TLS-mediated RGS is specifically observed in several cancer cell lines and contributes to their survival. Thus, targeting TLS has the potential to uniquely eradicate tumors without harming non-cancer tissues. Areas Covered: This review provides an innovative perspective on the role of TLS beyond its canonical function of lesion bypass or post-replicative gap filling. We provide a comprehensive analysis that underscores the emerging role of TLS as a cancer adaptation necessary to overcome the replication stress response (RSR), an anti-cancer barrier. Expert Opinion: TLS RGS is critical for tumorigenesis and is a new hallmark of cancer. Although the exact mechanism and extent of TLS dependency in cancer is still emerging, TLS inhibitors have shown promise as an anti-cancer therapy in selectively targeting this unique cancer vulnerability.

Keywords:  DNA lesion bypass; Translesion synthesis (TLS); cancer and cancer therapeutics; mutagenesis; oncogene-induced replication stress; replication gap suppression (RGS); replication stress response (RSR); ssDNA gaps

DOI:  https://doi.org/10.1080/14728222.2021.1864321
Curr Biol. 2021 Jan 05. pii: S0960-9822(20)31838-8. [Epub ahead of print]

Ligation of newly replicated DNA controls the timing of DNA mismatch repair.

Gloria X Reyes, Anna Kolodziejczak, Lovely Jael Paul Solomon Devakumar, Takashi Kubota, Richard D Kolodner, Christopher D Putnam, Hans Hombauer.

  Mismatch repair (MMR) safeguards genome stability through recognition and excision of DNA replication errors.1-4 How eukaryotic MMR targets the newly replicated strand in vivo has not been established. MMR reactions reconstituted in vitro are directed to the strand containing a preexisting nick or gap,5-8 suggesting that strand discontinuities could act as discrimination signals. Another candidate is the proliferating cell nuclear antigen (PCNA) that is loaded at replication forks and is required for the activation of Mlh1-Pms1 endonuclease.7-9 Here, we discovered that overexpression of DNA ligase I (Cdc9) in Saccharomyces cerevisiae causes elevated mutation rates and increased chromatin-bound PCNA levels and accumulation of Pms1 foci that are MMR intermediates, suggesting that premature ligation of replication-associated nicks interferes with MMR. We showed that yeast Pms1 expression is mainly restricted to S phase, in agreement with the temporal coupling between MMR and DNA replication.10 Restricting Pms1 expression to the G2/M phase caused a mutator phenotype that was exacerbated in the absence of the exonuclease Exo1. This mutator phenotype was largely suppressed by increasing the lifetime of replication-associated DNA nicks, either by reducing or delaying Cdc9 ligase activity in vivo. Therefore, Cdc9 dictates a window of time for MMR determined by transient DNA nicks that direct the Mlh1-Pms1 in a strand-specific manner. Because DNA nicks occur on both newly synthesized leading and lagging strands,11 these results establish a general mechanism for targeting MMR to the newly synthesized DNA, thus preventing the accumulation of mutations that underlie the development of human cancer.

Keywords:  Cdc9; DNA ligase I; DNA ligase I overexpression; DNA replication fidelity; DNA replication-associated nicks; MMR; MMR strand discrimination signal; ligation Okazaki fragments; mismatch repair; mutation accumulation

DOI:  https://doi.org/10.1016/j.cub.2020.12.018
Elife. 2021 Jan 05. pii: e63589. [Epub ahead of print]10

Checkpoint inhibition of origin firing prevents inappropriate replication outside of S-phase.

Mark C Johnson, Geylani Can, Miguel Monteiro Santos, Diana Alexander, Philip Zegerman.

  Checkpoints maintain the order of cell cycle events during DNA damage or incomplete replication. How the checkpoint response is tailored to different phases of the cell cycle remains poorly understood. The S-phase checkpoint for example results in the slowing of replication, which in budding yeast occurs by Rad53-dependent inhibition of the initiation factors Sld3 and Dbf4. Despite this, we show here that Rad53 phosphorylates both of these substrates throughout the cell cycle at the same sites as in S-phase, suggesting roles for this pathway beyond S-phase. Indeed, we show that Rad53-dependent inhibition of Sld3 and Dbf4 limits re-replication in G2/M, preventing gene amplification. In addition, we show that inhibition of Sld3 and Dbf4 in G1 prevents premature initiation at all origins at the G1/S transition. This study redefines the scope of the 'S-phase checkpoint' with implications for understanding checkpoint function in cancers that lack cell cycle controls.

Keywords:  S. cerevisiae; chromosomes; gene expression

DOI:  https://doi.org/10.7554/eLife.63589
ACS Infect Dis. 2021 Jan 08.

A Mitochondrial Orthologue of the dNTP Triphosphohydrolase SAMHD1 Is Essential and Controls Pyrimidine Homeostasis in Trypanosoma brucei.

Miriam Yagüe-Capilla, Víctor M Castillo-Acosta, Cristina Bosch-Navarrete, Luis Miguel Ruiz-Pérez, Dolores González-Pacanowska.

  The maintenance of deoxyribonucleotide triphosphate (dNTP) homeostasis through synthesis and degradation is critical for accurate genomic and mitochondrial DNA replication fidelity. Trypanosoma brucei makes use of both the salvage and de novo pathways for the provision of pyrimidine dNTPs. In this respect, the sterile α motif and histidine-aspartate domain-containing protein 1 (SAMHD1) appears to be the most relevant dNTPase controlling dNTP/deoxynucleoside homeostasis in mammalian cells. Here, we have characterized the role of a unique trypanosomal SAMHD1 orthologue denominated TbHD52. Our results show that TbHD52 is a mitochondrial enzyme essential in bloodstream forms of T. brucei. Knockout cells are pyrimidine auxotrophs that exhibit strong defects in genomic integrity, cell cycle progression, and nuclear DNA and kinetoplast segregation in the absence of extracellular thymidine. The lack of TbHD52 can be counteracted by the overexpression of human dCMP deaminase, an enzyme that is directly involved in dUMP formation yet absent in trypanosomes. Furthermore, the cellular dNTP quantification and metabolomic analysis of TbHD52 null mutants revealed perturbations in the nucleotide metabolism with a substantial accumulation of dCTP and cytosine-derived metabolites while dTTP formation was significantly reduced. We propose that this HD-domain-containing protein unique to kinetoplastids plays an essential role in pyrimidine dNTP homeostasis and contributes to the provision of deoxycytidine required for cellular dTTP biosynthesis.

Keywords:  Trypanosoma brucei; mitochondria; nucleotide; pyrimidine metabolism; thymidylate biosynthesis

DOI:  https://doi.org/10.1021/acsinfecdis.0c00551
Cell Rep. 2021 Jan 05. pii: S2211-1247(20)31554-0. [Epub ahead of print]34(1): 108565

MRE11-RAD50-NBS1 Complex Is Sufficient to Promote Transcription by RNA Polymerase II at Double-Strand Breaks by Melting DNA Ends.

Sheetal Sharma, Roopesh Anand, Xuzhu Zhang, Sofia Francia, Flavia Michelini, Alessandro Galbiati, Hannah Williams, Daryl A Ronato, Jean-Yves Masson, Eli Rothenberg, Petr Cejka, Fabrizio d'Adda di Fagagna.

  The MRE11-RAD50-NBS1 (MRN) complex supports the synthesis of damage-induced long non-coding RNA (dilncRNA) by RNA polymerase II (RNAPII) from DNA double-strand breaks (DSBs) by an unknown mechanism. Here, we show that recombinant human MRN and native RNAPII are sufficient to reconstitute a minimal functional transcriptional apparatus at DSBs. MRN recruits and stabilizes RNAPII at DSBs. Unexpectedly, transcription is promoted independently from MRN nuclease activities. Rather, transcription depends on the ability of MRN to melt DNA ends, as shown by the use of MRN mutants and specific allosteric inhibitors. Single-molecule FRET assays with wild-type and mutant MRN show a tight correlation between the ability to melt DNA ends and to promote transcription. The addition of RPA enhances MRN-mediated transcription, and unpaired DNA ends allow MRN-independent transcription by RNAPII. These results support a model in which MRN generates single-strand DNA ends that favor the initiation of transcription by RNAPII.

Keywords:  DNA damage; DNA double-strand breaks; DNA melting; DNA-damage induced transcription; MRE11-RAD50-NBS1 complex; RNA polymerase II; damage-induced long non-coding RNA; dilncRNA; in vitro transcription; single-molecule FRET

DOI:  https://doi.org/10.1016/j.celrep.2020.108565
Nucleic Acids Res. 2021 Jan 06. pii: gkaa1232. [Epub ahead of print]

SUMOylation mediates CtIP's functions in DNA end resection and replication fork protection.

Andrew J Locke, Lazina Hossain, Glynnis McCrostie, Daryl A Ronato, Amira Fitieh, Tanzeem Ahmed Rafique, Fatemeh Mashayekhi, Mobina Motamedi, Jean-Yves Masson, Ismail Hassan Ismail.

Double-strand breaks and stalled replication forks are a significant threat to genomic stability that can lead to chromosomal rearrangements or cell death. The protein CtIP promotes DNA end resection, an early step in homologous recombination repair, and has been found to protect perturbed forks from excessive nucleolytic degradation. However, it remains unknown how CtIP's function in fork protection is regulated. Here, we show that CtIP recruitment to sites of DNA damage and replication stress is impaired upon global inhibition of SUMOylation. We demonstrate that CtIP is a target for modification by SUMO-2 and that this occurs constitutively during S phase. The modification is dependent on the activities of cyclin-dependent kinases and the PI-3-kinase-related kinase ATR on CtIP's carboxyl-terminal region, an interaction with the replication factor PCNA, and the E3 SUMO ligase PIAS4. We also identify residue K578 as a key residue that contributes to CtIP SUMOylation. Functionally, a CtIP mutant where K578 is substituted with a non-SUMOylatable arginine residue is defective in promoting DNA end resection, homologous recombination, and in protecting stalled replication forks from excessive nucleolytic degradation. Our results shed further light on the tightly coordinated regulation of CtIP by SUMOylation in the maintenance of genome stability.

DOI: https://doi.org/10.1093/nar/gkaa1232
Life Sci Alliance. 2021 Mar;pii: e202000980. [Epub ahead of print]4(3):

Cyclin A2 localises in the cytoplasm at the S/G2 transition to activate PLK1.

Helena Silva Cascales, Kamila Burdova, Anna Middleton, Vladislav Kuzin, Erik Müllers, Henriette Stoy, Laura Baranello, Libor Macurek, Arne Lindqvist.

Cyclin A2 is a key regulator of the cell cycle, implicated both in DNA replication and mitotic entry. Cyclin A2 participates in feedback loops that activate mitotic kinases in G2 phase, but why active Cyclin A2-CDK2 during the S phase does not trigger mitotic kinase activation remains unclear. Here, we describe a change in localisation of Cyclin A2 from being only nuclear to both nuclear and cytoplasmic at the S/G2 border. We find that Cyclin A2-CDK2 can activate the mitotic kinase PLK1 through phosphorylation of Bora, and that only cytoplasmic Cyclin A2 interacts with Bora and PLK1. Expression of predominately cytoplasmic Cyclin A2 or phospho-mimicking PLK1 T210D can partially rescue a G2 arrest caused by Cyclin A2 depletion. Cytoplasmic presence of Cyclin A2 is restricted by p21, in particular after DNA damage. Cyclin A2 chromatin association during DNA replication and additional mechanisms contribute to Cyclin A2 localisation change in the G2 phase. We find no evidence that such mechanisms involve G2 feedback loops and suggest that cytoplasmic appearance of Cyclin A2 at the S/G2 transition functions as a trigger for mitotic kinase activation.

DOI: https://doi.org/10.26508/lsa.202000980
Redox Biol. 2020 Dec 28. pii: S2213-2317(20)31055-7. [Epub ahead of print]40 101850

The toxic side of one-carbon metabolism and epigenetics.

Agustín E Morellato, Carla Umansky, Lucas B Pontel.

  One-carbon metabolism is a central metabolic hub that provides one-carbon units for essential biosynthetic reactions and for writing epigenetics marks. The leading role in this hub is performed by the one-carbon carrier tetrahydrofolate (THF), which accepts formaldehyde usually from serine generating one-carbon THF intermediates in a set of reactions known as the folate or one-carbon cycle. THF derivatives can feed one-carbon units into purine and thymidine synthesis, and into the methionine cycle that produces the universal methyl-donor S-adenosylmethionine (AdoMet). AdoMet delivers methyl groups for epigenetic methylations and it is metabolized to homocysteine (Hcy), which can enter the transsulfuration pathway for the production of cysteine and lastly glutathione (GSH), the main cellular antioxidant. This vital role of THF comes to an expense. THF and other folate derivatives are susceptible to oxidative breakdown releasing formaldehyde, which can damage DNA -a consequence prevented by the Fanconi Anaemia DNA repair pathway. Epigenetic demethylations catalysed by lysine-specific demethylases (LSD) and Jumonji histone demethylases can also release formaldehyde, constituting a potential threat for genome integrity. In mammals, the toxicity of formaldehyde is limited by a metabolic route centred on the enzyme alcohol dehydrogenase 5 (ADH5/GSNOR), which oxidizes formaldehyde conjugated to GSH, lastly generating formate. Remarkably, this formate can be a significant source of one-carbon units, thus defining a formaldehyde cycle that likely restricts the toxicity of one-carbon metabolism and epigenetic demethylations. This work describes recent advances in one-carbon metabolism and epigenetics, focusing on the steps that involve formaldehyde flux and that might lead to cytotoxicity affecting human health.

Keywords:  ADH5; Epigenetics; Fanconi anemia; Formaldehyde; Glutathione; One-carbon metabolism

DOI:  https://doi.org/10.1016/j.redox.2020.101850
J Cell Sci. 2021 Jan 06. pii: jcs.247809. [Epub ahead of print]

Poly(ADP-ribosyl)ation temporally confines SUMO-dependent ataxin-3 recruitment to control DNA double-strand break repair.

Annika Pfeiffer, Laura K Herzog, Martijn S Luijsterburg, Rashmi G Shah, Magdalena B Rother, Henriette Stoy, Ulrike Kühbacher, Haico van Attikum, Girish M Shah, Nico P Dantuma.

  DNA damage-induced SUMOylation serves as a signal for two antagonizing proteins that both stimulate repair of DNA double strand breaks (DSBs). Here, we demonstrate that the SUMO-dependent recruitment of the deubiquitylating enzyme ataxin-3 to DSBs, unlike recruitment of the ubiquitin ligase RNF4, additionally depends on PARP1-mediated poly(ADP-ribosyl)ation (PARylation). The co-dependence of ataxin-3 recruitment on PARylation and SUMOylation temporally confines its presence at DSBs to a short time window directly following detection of the DNA damage. We propose that this mechanism ensures that ataxin-3 prevents the premature removal of DNA repair proteins only during the early phase of the DSB response and does not interfere with the subsequent timely displacement of DNA repair proteins by RNF4. Thus, our data show that PARylation differentially regulates SUMO-dependent recruitment of ataxin-3 and RNF4 to DSBs, explaining how both proteins can play a stimulatory role at DSBs despite their opposing activities.

Keywords:  Ataxin-3; DNA damage response; PARylation; RNF4; SUMO; Ubiquitin

DOI:  https://doi.org/10.1242/jcs.247809
Front Cell Dev Biol. 2020 ;8 602956

ATR Kinase Is a Crucial Player Mediating the DNA Damage Response in Trypanosoma brucei.

Paula Andrea Marin, Ricardo Obonaga, Raphael Souza Pavani, Marcelo Santos da Silva, Christiane Bezerra de Araujo, André Arruda Lima, Carla Cristi Avila, Igor Cestari, Carlos Renato Machado, Maria Carolina Elias.

  DNA double-strand breaks (DSBs) are among the most deleterious lesions that threaten genome integrity. To address DSBs, eukaryotic cells of model organisms have evolved a complex network of cellular pathways that are able to detect DNA damage, activate a checkpoint response to delay cell cycle progression, recruit the proper repair machinery, and resume the cell cycle once the DNA damage is repaired. Cell cycle checkpoints are primarily regulated by the apical kinases ATR and ATM, which are conserved throughout the eukaryotic kingdom. Trypanosoma brucei is a divergent pathogenic protozoan parasite that causes human African trypanosomiasis (HAT), a neglected disease that can be fatal when left untreated. The proper signaling and accuracy of DNA repair is fundamental to T. brucei not only to ensure parasite survival after genotoxic stress but also because DSBs are involved in the process of generating antigenic variations used by this parasite to evade the host immune system. DSBs trigger a strong DNA damage response and efficient repair process in T. brucei, but it is unclear how these processes are coordinated. Here, by knocking down ATR in T. brucei using two different approaches (conditional RNAi and an ATR inhibitor), we show that ATR is required to mediate intra-S and partial G1/S checkpoint responses. ATR is also involved in replication fork stalling, is critical for H2A histone phosphorylation in a small group of cells and is necessary for the recruitment and upregulation of the HR-mediated DNA repair protein RAD51 after ionizing radiation (IR) induces DSBs. In summary, this work shows that apical ATR kinase plays a central role in signal transduction and is critical for orchestrating the DNA damage response in T. brucei.

Keywords:  ATR; DNA damage response; DNA double-strand breaks; RAD51; Trypanosoma brucei; checkpoint; γH2A

DOI:  https://doi.org/10.3389/fcell.2020.602956
Chem Res Toxicol. 2021 Jan 06.

Base and Nucleotide Excision Repair Pathways in DNA Plasmids Harboring Oxidatively Generated Guanine Lesions.

Marina Kolbanovskiy, Abraham Aharonoff, Ana Helena Sales, Nicholas E Geacintov, Vladimir Shafirovich.

The base and nucleotide excision repair pathways (BER and NER, respectively) are two major mechanisms that remove DNA lesions formed by the reactions of genotoxic intermediates with cellular DNA. We have demonstrated earlier that the oxidatively generated guanine lesions spiroiminodihydantoin (Sp) and 5-guanidinohydantoin (Gh) are excised from double-stranded DNA by competing BER and NER in whole-cell extracts [Shafirovich, V., et al. (2016) J. Biol. Chem. 321, 5309-5319]. In this work we compared the NER and BER yields with single Gh or Sp lesions embedded at the same sites in covalently closed circular pUC19NN plasmid DNA (cccDNA) and in the same but linearized form (linDNA) of this plasmid. The kinetics of the Sp and Gh BER and NER incisions were monitored in HeLa cell extracts. The yield of NER products is ∼5 times greater in covalently closed circular DNA than in the linearized form, while the BER yield is smaller by ∼20-30% depending on the guanine lesion. Control BER experiments with 8-oxo-7,8-dihydroguanine (8-oxoG) show that the BER yield is increased by a factor of only 1.4 ± 0.2 in cccDNA relative to linDNA. These surprising differences in BER and NER activities are discussed in terms of the lack of termini in covalently closed circular DNA and the DNA lesion search dynamics of the NER DNA damage sensor XPC-RAD23B and the BER enzyme OGG1 that recognizes and excises 8-oxoG.

DOI: https://doi.org/10.1021/acs.chemrestox.0c00463
Commun Biol. 2021 Jan 04. 4(1): 11

DNA-protein crosslink proteases in genome stability.

Annamaria Ruggiano, Kristijan Ramadan.

Proteins covalently attached to DNA, also known as DNA-protein crosslinks (DPCs), are common and bulky DNA lesions that interfere with DNA replication, repair, transcription and recombination. Research in the past several years indicates that cells possess dedicated enzymes, known as DPC proteases, which digest the protein component of a DPC. Interestingly, DPC proteases also play a role in proteolysis beside DPC repair, such as in degrading excess histones during DNA replication or controlling DNA replication checkpoints. Here, we discuss the importance of DPC proteases in DNA replication, genome stability and their direct link to human diseases and cancer therapy.

DOI: https://doi.org/10.1038/s42003-020-01539-3
ChemMedChem. 2021 Jan 06.

Discovery of a novel inhibitor of human purine nucleoside phosphorylase by a simple hydrophilic interaction liquid chromatography (HILIC-UV) enzymatic assay.

Marco Rabuffetti, Francesca Rinaldi, Alessandra Lo Bianco, Giovanna Speranza, Daniela Ubiali, Marcela Cristina de Moraes, Luiz Claudio Rodrigues Pereira da Silva, Gabriella Massolini, Enrica Calleri, Antonio Lavecchia.

  Purine nucleoside phosphorylase (PNP) belongs to the human purine salvage pathway. Genetic deficiency of this enzyme triggers apoptosis of activated T-cells due to the accumulation of deoxyguanosine triphosphate (dGTP). Therefore, potential chemotherapeutic applications of human PNP inhibitors includes the treatment of T-cell leukemia, autoimmune diseases and transplant tissue rejection. In this report, we present the discovery of novel human PNP ( Hs PNP) inhibitors by coupling experimental and computational tools. A simple, economic, direct and non-radioactive enzymatic assay coupled to hydrophilic interaction liquid chromatography and UV detection (HILIC-UV) was developed for experimental screening of Hs PNP inhibitors. Enzymatic reactions were performed in batch and activity was assessed by monitoring the phosphorolysis of inosine (Ino) to hypoxanthine (Hpx) by HILIC-UV. A small library of 6- and 8-substituted nucleosides was synthesized and screened. The inhibition potency of the most promising compound, 8-aminoinosine ( 4 ), was quantified through K i and IC 50 determinations. The effect of Hs PNP inhibition was also evaluated in vitro through the study of cytotoxicity on human T-cell leukemia cells (CCRF-CEM). We also carried out docking studies for the most potent compound allowing further insights into the inhibitor interaction of Hs PNP active site. This study provides both new tools and a new lead for developing novel Hs PNP inhibitors.

Keywords:  PNP inhibitors, screening, enzymatic assay, antitumour activity, drug discovery

DOI:  https://doi.org/10.1002/cmdc.202000874
Cancer Chemother Pharmacol. 2021 Jan 05.

Enhancing the activity of platinum-based drugs by improved inhibitors of ERCC1-XPF-mediated DNA repair.

Gloria Ciniero, Ahmed H Elmenoufy, Francesco Gentile, Michael Weinfeld, Marco A Deriu, Frederick G West, Jack A Tuszynski, Charles Dumontet, Emeline Cros-Perrial, Lars Petter Jordheim.

   PURPOSE: The ERCC1-XPF 5'-3' DNA endonuclease complex is involved in the nucleotide excision repair pathway and in the DNA inter-strand crosslink repair pathway, two key mechanisms modulating the activity of chemotherapeutic alkylating agents in cancer cells. Inhibitors of the interaction between ERCC1 and XPF can be used to sensitize cancer cells to such drugs.
METHODS: We tested recently synthesized new generation inhibitors of this interaction and evaluated their capacity to sensitize cancer cells to the genotoxic activity of agents in synergy studies, as well as their capacity to inhibit the protein-protein interaction in cancer cells using proximity ligation assay.
RESULTS: Compound B9 showed the best activity being synergistic with cisplatin and mitomycin C in both colon and lung cancer cells. Also, B9 abolished the interaction between ERCC1 and XPF in cancer cells as shown by proximity ligation assay. Results of different compounds correlated with values from our previously obtained in silico predictions.
CONCLUSION: Our results confirm the feasibility of the approach of targeting the protein-protein interaction between ERCC1 and XPF to sensitize cancer cells to alkylating agents, thanks to the improved binding affinity of the newly synthesized compounds.

Keywords:  Cancer; Chemical synthesis; DNA repair; Protein–protein interaction

DOI:  https://doi.org/10.1007/s00280-020-04213-x
J Biomed Sci. 2021 Jan 04. 28(1): 2

O6-methylguanine-DNA methyltransferase modulates cisplatin-induced DNA double-strand breaks by targeting the homologous recombination pathway in nasopharyngeal carcinoma.

Shang-Hung Chen, Wen-Tsung Huang, Wan-Chen Kao, Sheng-Yen Hsiao, Hsin-Yi Pan, Chin-Wen Fang, Yow-Ling Shiue, Chia-Lin Chou, Chien-Feng Li.

   BACKGROUND: The homologous recombination (HR) pathway is involved in DNA damage response (DDR), which is crucial to cancer cell survival after treatment with DNA damage agents. O6-methylguanine DNA methyltransferase (MGMT) is associated with cisplatin (CDDP) resistance in cancer cells; however, the underlying mechanisms remain unclear. Here, we explored the interactions between MGMT and the HR pathway in CDDP-activated DDR and their clinical implications in nasopharyngeal carcinoma (NPC).
METHODS: Human NPC cells were assessed using loss-of-function approaches in vitro. The expression correlations between MGMT and major proteins of the HR pathway were analyzed through Western blotting, quantitative real-time PCR, and bioinformatic analysis by using a public database. The physical interactions between MGMT and HR proteins were studied using co-immunoprecipitation and immunofluorescence analyses. Cell comet tails and γ-H2AX expression levels were examined to evaluate double-strand break (DSB) formation. Established immunofluorescence and reporter analyses were conducted to measure HR activity. Xenograft and cell viability studies were used to assess the therapeutic potential of MGMT inhibition in combination with CDDP and poly(ADP-ribose) polymerase (PARP) inhibitor, respectively.
RESULTS: Among major proteins of the HR pathway, MGMT suppression inhibited CDDP-induced RAD51 expression. Bioinformatic analyses showed a positive correlation between MGMT and RAD51 expression in patients with NPC. Moreover, MGMT physically interacted with BRCA1 and regulated CDDP-induced BRCA1 phosphorylation (ser 988). In functional assays, MGMT inhibition increased CDDP-induced DSB formation through attenuation of HR activity. NPC xenograft studies demonstrated that MGMT inhibition combined with CDDP treatment reduced tumor size and downregulated RAD51 expression and BRCA1 phosphorylation. Furthermore, MGMT suppression increased PARP inhibitor-induced cell death and DSB formation in NPC cells.
CONCLUSION: MGMT is crucial in the activation of the HR pathway and regulates DDR in NPC cells treated with CDDP and PARP inhibitor. Thus, MGMT is a promising therapeutic target for cancer treatments involving HR-associated DDR.

Keywords:  Cisplatin; Homologous recombination; MGMT; Nasopharyngeal carcinoma; PARP inhibitor

DOI:  https://doi.org/10.1186/s12929-020-00699-y
BMC Res Notes. 2021 Jan 07. 14(1): 19

Resveratrol induces H3 and H4K16 deacetylation and H2A.X phosphorylation in Toxoplasma gondii.

Susana M Contreras, Agustina Ganuza, María M Corvi, Sergio O Angel.

   OBJECTIVE: Resveratrol (RSV) is a multitarget drug that has demonstrated activity against Toxoplasma gondii in macrophage and human foreskin fibroblast (HFF) cell line infection models. However, the mechanism of action of RSV has not yet been determined. Thus, with the aim of identifying a possible mechanism of the anti-T. gondii activity of this compound, we analyzed the effects of RSV on histones H3 and H4 lysine 16 acetylation (H4K16). We also analyzed RSV-induced DNA damage to intracellular tachyzoites by using the DNA damage marker phosphorylated histone H2A.X (γH2AX).
RESULTS: RSV inhibited intracellular T. gondii tachyzoite growth at concentrations below the toxic threshold for host cells. The IC50 value after 24 h of treatment was 53 μM. RSV induced a reduction in H4K16 acetylation (H4K16ac), a marker associated with transcription, DNA replication and homologous recombination repair. A similar deacetylation effect was observed on histone H3. RSV also increased T. gondii H2A.X phosphorylation at the SQE motif (termed γH2A.X), which is a DNA damage-associated posttranslational modification. Our findings suggest a possible link between RSV and DNA damage or repair processes that is possibly associated with DNA replication stress.

Keywords:  Chromatin remodeling; DNA damage; H2A.X; Histone deacetylase; Resveratrol; Toxoplasma gondii; Treatment

DOI:  https://doi.org/10.1186/s13104-020-05416-4
Structure. 2020 Dec 30. pii: S0969-2126(20)30473-1. [Epub ahead of print]

The active DNA-PK holoenzyme occupies a tensed state in a staggered synaptic complex.

Morgan Hepburn, Daniel J Saltzberg, Linda Lee, Shujuan Fang, Claire Atkinson, Natalie C J Strynadka, Andrej Sali, Susan P Lees-Miller, David C Schriemer.

  In the non-homologous end-joining (NHEJ) of a DNA double-strand break, DNA ends are bound and protected by DNA-PK, which synapses across the break to tether the broken ends and initiate repair. There is little clarity surrounding the nature of the synaptic complex and the mechanism governing the transition to repair. We report an integrative structure of the synaptic complex at a precision of 13.5 Å, revealing a symmetric head-to-head arrangement with a large offset in the DNA ends and an extensive end-protection mechanism involving a previously uncharacterized plug domain. Hydrogen/deuterium exchange mass spectrometry identifies an allosteric pathway connecting DNA end-binding with the kinase domain that places DNA-PK under tension in the kinase-active state. We present a model for the transition from end-protection to repair, where the synaptic complex supports hierarchical processing of the ends and scaffold assembly, requiring displacement of the catalytic subunit and tension release through kinase activity.

Keywords:  DNA repair; DNA-PK; crosslinking mass spectrometry; hydrogen/deuterium exchange; modeling; non-homologous end-joining; structure; synaptic complex

DOI:  https://doi.org/10.1016/j.str.2020.12.006
Gene Ther. 2021 Jan 07.

FEN1 inhibitor synergizes with low-dose camptothecin to induce increased cell killing via the mitochondria mediated apoptotic pathway.

Ting Wu, Hongqiao Zhu, Miaomiao Zhang, Yuling Sun, Yongjing Yang, Lili Gu, Jing Zhang, Dan Mu, Congye Wu, Zhigang Hu, Longwei Jiang, Shaochang Jia, Ying Zhang, Lingfeng He, Fei-Yan Pan, Zhigang Guo.

Camptothecin has been used in tumor therapy for a long time but its antitumor effect is rather limited due to the side effect and the drug resistance. FEN1, a major component of DNA repair systems, plays important roles in maintaining genomic stability via DNA replication and repair. Here we found that FEN1 inhibitor greatly sensitizes cancer cells to low-dose camptothecin. The combinative treatment of FEN1 inhibitor and 1 nM camptothecin induced a synthetic lethal effect, which synergistically suppressed cancer cell proliferation and significantly mediated apoptosis both in vitro and in vivo. Our study suggested that targeting FEN1 could be a potent strategy for tumor-targeting cancer therapy.

DOI: https://doi.org/10.1038/s41434-020-00215-9
Acta Pharmacol Sin. 2021 Jan 07.

Targeting DNA-PK overcomes acquired resistance to third-generation EGFR-TKI osimertinib in non-small-cell lung cancer.

Xing-Mei Liang, Qiong Qin, Bo-Ning Liu, Xiao-Qing Li, Li-Li Zeng, Jing Wang, Ling-Ping Kong, Dian-Sheng Zhong, Lin-Lin Sun.

  The third-generation of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), represented by osimertinib, has achieved remarkable clinical outcomes in the treatment of non-small-cell lung cancer (NSCLC) with EGFR mutation. However, resistance eventually emerges in most patients and the underlying molecular mechanisms remain to be fully understood. In this study, we generated an osimertinib-acquired resistant lung cancer model from a NSCLC cell line H1975 harboring EGFR L858R and T790M mutations. We found that the capacity of DNA damage repair was compromised in the osimertinib resistant cells, evidenced by increased levels of γH2AX and higher intensity of the comet tail after withdrawal from cisplatin. Pharmacological inhibiting the activity or genetic knockdown the expression of DNA-PK, a key kinase in DNA damage response (DDR), sensitized the resistant cells to osimertinib. Combination of osimertinib with the DNA-PK inhibitor, PI-103, or NU7441, synergistically suppressed the proliferation of the resistant cells. Mechanistically, we revealed that DNA-PK inhibitor in combination with osimertinib resulted in prolonged DNA damage and cell cycle arrest. These findings shed new light on the mechanisms of osimertinib resistance in the aspect of DNA repair, and provide a rationale for targeting DNA-PK as a therapeutic strategy to overcome osimertinib-acquired resistance in NSCLC.

Keywords:  DNA damage repair; DNA-PK; EGFR-TKI resistance; NSCLC; osimertinib

DOI:  https://doi.org/10.1038/s41401-020-00577-1
Cancer Res. 2021 Jan 06. pii: canres.2931.2020. [Epub ahead of print]

A spatial and functional interaction of a heterotetramer Survivin-DNA-PKcs complex in DNA damage response.

Ömer Güllülü, Stephanie Hehlgans, Benjamin E Mayer, Ines Gößner, Chrysi Petraki, Melanie Hoffmann, Maximilian J Dombrowsky, Patrick Kunzmann, Kay Hamacher, Klaus Strebhardt, Emmanouil Fokas, Claus Rödel, Christian Münch, Franz Rödel.

Substantial evidence has shown that overexpression of the inhibitor of apoptosis protein (IAP) Survivin in human tumors correlates significantly with treatment resistance and poor patient prognosis. Survivin serves as a radiation resistance factor that impacts the DNA damage response by interacting with DNA-dependent protein kinase (DNA-PKcs). However, the complexity, molecular determinants and functional consequences of this interrelationship remain largely unknown. By applying co-immunoprecipitation and flow cytometry-based Förster resonance energy transfer assays, we demonstrated a direct involvement of the Survivin baculovirus IAP repeat (BIR) domain in the regulation of radiation survival and DNA repair. This Survivin-mediated activity required an interaction of residues S20 and W67 with the phosphoinositide 3-kinase (PI3K) domain of DNA-PKcs. In silico molecular docking and dynamics simulation analyses, in vitro kinase assays, and large-scale mass spectrometry suggested a heterotetrameric Survivin-DNA-PKcs complex that results in a conformational change within the DNA-PKcs PI3K domain. Overexpression or depletion of Survivin resulted in enhanced PI3K enzymatic activity and detection of differentially abundant phosphopeptides and proteins implicated in the DNA damage response. The Survivin-DNA-PKcs interaction altered the S/T-hydrophobic motif substrate specificity of DNA-PKcs with a predominant usage of S/T-P phosphorylation sites and an increase of DNA-PKcs substrates including Foxo3. These data demonstrate that Survivin differentially regulates DNA-PKcs-dependent radiation survival and DNA double-strand break repair via formation of a Survivin-DNA-PKcs heterotetrameric complex.

DOI: https://doi.org/10.1158/0008-5472.CAN-20-2931
DNA Repair (Amst). 2020 Dec 30. pii: S1568-7864(20)30291-3. [Epub ahead of print]98 103031

A large intermediate domain of vertebrate REV3 protein is dispensable for ultraviolet-induced translesion replication.

Jun Takezawa, Anna Shimazaki, Hidemi Takimoto, Kagemasa Kajiwara, Kouichi Yamada.

  DNA polymerase ζ (pol ζ) is involved in translesion replication (translesion synthesis, TLS) and plays an essential role in embryogenesis. In adults, pol ζ triggers mutation as a result of error-prone TLS and causes carcinogenesis. The catalytic subunit of pol ζ, REV3, is evolutionarily conserved from yeast and plants to higher eukaryotes. However, the structures are notably different: unlike that in yeast REV3, a large intermediate domain is inserted in REV3 of humans and mice. The domain is mostly occupied with noncommittal structures (random coil…etc.); therefore, its role and function are yet to be resolved. Previously, we reported deficient levels of ultraviolet (UV)-induced TLS in fibroblasts derived from the Rev3-knockout mouse embryo (Rev3KO-MEF). Here, we constructed a mouse Rev3-expressing plasmid with a deleted intermediate domain (532-1793 a.a,) and transfected it into Rev3KO-MEF. The isolated stable transformants showed comparable levels of UV-sensitivity and UV-TLS activity to those in wild-type MEF, detected using an alkaline sucrose density gradient sedimentation. These results indicate that the intermediate domain is nonessential for UV-induced translesion replication in cultured mouse cells.

Keywords:  DNA polymerase ζ; KIAA2022; Rev3 knockout; Sez4; TLS; Translesion replication

DOI:  https://doi.org/10.1016/j.dnarep.2020.103031
Nat Commun. 2021 01 04. 12(1): 20

The ATM and ATR kinases regulate centrosome clustering and tumor recurrence by targeting KIFC1 phosphorylation.

Guangjian Fan, Lianhui Sun, Ling Meng, Chen Hu, Xing Wang, Zhan Shi, Congli Hu, Yang Han, Qingqing Yang, Liu Cao, Xiaohong Zhang, Yan Zhang, Xianmin Song, Shujie Xia, Baokun He, Shengping Zhang, Chuangui Wang.

Drug resistance and tumor recurrence are major challenges in cancer treatment. Cancer cells often display centrosome amplification. To maintain survival, cancer cells achieve bipolar division by clustering supernumerary centrosomes. Targeting centrosome clustering is therefore considered a promising therapeutic strategy. However, the regulatory mechanisms of centrosome clustering remain unclear. Here we report that KIFC1, a centrosome clustering regulator, is positively associated with tumor recurrence. Under DNA damaging treatments, the ATM and ATR kinases phosphorylate KIFC1 at Ser26 to selectively maintain the survival of cancer cells with amplified centrosomes via centrosome clustering, leading to drug resistance and tumor recurrence. Inhibition of KIFC1 phosphorylation represses centrosome clustering and tumor recurrence. This study identified KIFC1 as a prognostic tumor recurrence marker, and revealed that tumors can acquire therapeutic resistance and recurrence via triggering centrosome clustering under DNA damage stresses, suggesting that blocking KIFC1 phosphorylation may open a new vista for cancer therapy.

DOI: https://doi.org/10.1038/s41467-020-20208-x
Exp Hematol Oncol. 2021 Jan 04. 10(1): 3

Targeting phosphoglycerate dehydrogenase in multiple myeloma.

Samah Elsaadi, Ida Steiro, Pegah Abdollahi, Esten N Vandsemb, Rui Yang, Tobias S Slørdahl, Torstein Baade Rø, Eline Menu, Anne-Marit Sponaas, Magne Børset.

   BACKGROUND: Multiple myeloma (MM) is a hematological malignancy characterized by the clonal expansion of plasma cells in the bone marrow. To date, this disease is still incurable and novel therapeutic approaches are required. Phosphoglycerate dehydrogenase (PHGDH) is the first and rate-limiting enzyme in the de novo serine synthesis pathway, and it has been attributed to bortezomib-resistance in MM.
METHODS: Two different PHGDH inhibitors, CBR5884 and NCT-503, were tested against human myeloma cell lines, primary MM cells from patients, and peripheral blood mononuclear cells isolated from healthy donors. The PHGDH inhibitors were then tested in combination with proteasome inhibitors in different MM cell lines, including proteasome-resistant cell lines. Furthermore, we confirmed the effects of PHGDH inhibition through knocking down PHGDH and the effect of NCT-503 in vivo in the 5T33MM mouse model.
RESULTS: All the tested myeloma cell lines expressed PHGDH and were sensitive to doses of NCT-503 that were tolerated by peripheral blood mononuclear cells isolated from healthy donors. Upon testing bortezomib in combination with NCT-503, we noticed a clear synergy in several HMCLs. The sensitivity to bortezomib also increased after PHGDH knockdown, mimicking the effect of NCT-503 treatment. Interestingly, targeting PHGDH reduced the intracellular redox capacity of the cells. Furthermore, combination treatment with NCT-503 and bortezomib exhibited a therapeutic advantage in vivo.
CONCLUSIONS: Our study shows the therapeutic potential of targeting PHGDH in MM, and suggest it as a way to overcome the resistance to proteasome inhibitors.

Keywords:  Bortezomib; Myeloma; NCT-503; PHGDH; Serine

DOI:  https://doi.org/10.1186/s40164-020-00196-w
Nucleic Acids Res. 2021 Jan 04. pii: gkaa1241. [Epub ahead of print]

Catalytically inactive Cas9 impairs DNA replication fork progression to induce focal genomic instability.

Goro Doi, Satoshi Okada, Takehiro Yasukawa, Yuki Sugiyama, Siqin Bala, Shintaro Miyazaki, Dongchon Kang, Takashi Ito.

Catalytically inactive Cas9 (dCas9) has become an increasingly popular tool for targeted gene activation/inactivation, live-cell imaging, and base editing. While dCas9 was reported to induce base substitutions and indels, it has not been associated with structural variations. Here, we show that dCas9 impedes replication fork progression to destabilize tandem repeats in budding yeast. When targeted to the CUP1 array comprising ∼16 repeat units, dCas9 induced its contraction in most cells, especially in the presence of nicotinamide. Replication intermediate analysis demonstrated replication fork stalling in the vicinity of dCas9-bound sites. Genetic analysis indicated that while destabilization is counteracted by the replisome progression complex components Ctf4 and Mrc1 and the accessory helicase Rrm3, it involves single-strand annealing by the recombination proteins Rad52 and Rad59. Although dCas9-mediated replication fork stalling is a potential risk in conventional applications, it may serve as a novel tool for both mechanistic studies and manipulation of genomic instability.

DOI: https://doi.org/10.1093/nar/gkaa1241
iScience. 2021 Jan 22. 24(1): 101935

Regulation of purine metabolism connects KCTD13 to a metabolic disorder with autistic features.

Jon M Madison, Karen Duong, Ellen F Vieux, Namrata D Udeshi, Sumaiya Iqbal, Elise Requadt, Shaunt Fereshetian, Michael C Lewis, Antonio S Gomes, Kerry A Pierce, Randall J Platt, Feng Zhang, Arthur J Campbell, Dennis Lal, Florence F Wagner, Clary B Clish, Steven A Carr, Morgan Sheng, Edward M Scolnick, Jeffrey R Cottrell.

  Genetic variation of the 16p11.2 deletion locus containing the KCTD13 gene and of CUL3 is linked with autism. This genetic connection suggested that substrates of a CUL3-KCTD13 ubiquitin ligase may be involved in disease pathogenesis. Comparison of Kctd13 mutant (Kctd13 -/- ) and wild-type neuronal ubiquitylomes identified adenylosuccinate synthetase (ADSS), an enzyme that catalyzes the first step in adenosine monophosphate (AMP) synthesis, as a KCTD13 ligase substrate. In Kctd13 -/- neurons, there were increased levels of succinyl-adenosine (S-Ado), a metabolite downstream of ADSS. Notably, S-Ado levels are elevated in adenylosuccinate lyase deficiency, a metabolic disorder with autism and epilepsy phenotypes. The increased S-Ado levels in Kctd13 -/- neurons were decreased by treatment with an ADSS inhibitor. Lastly, functional analysis of human KCTD13 variants suggests that KCTD13 variation may alter ubiquitination of ADSS. These data suggest that succinyl-AMP metabolites accumulate in Kctd13 -/- neurons, and this observation may have implications for our understanding of 16p11.2 deletion syndrome.

Keywords:  Metabolomics; Molecular Neuroscience; Proteomics

DOI:  https://doi.org/10.1016/j.isci.2020.101935
Biochem Pharmacol. 2021 Jan 04. pii: S0006-2952(21)00002-2. [Epub ahead of print] 114406

P2Y Receptors for Extracellular Nucleotides: Contributions to Cancer Progression and Therapeutic Implications.

Lucas T Woods, Kevin Muñoz Forti, Vinit C Shanbhag, Jean M Camden, Gary A Weisman.

  Purinergic receptors for extracellular nucleotides and nucleosides contribute to a vast array of cellular and tissue functions, including cell proliferation, intracellular and transmembrane ion flux, immunomodulation and thrombosis. In mammals, the purinergic receptor system is composed of G protein-coupled P1 receptors A1, A2A, A2B and A3 for extracellular adenosine, P2X1-7 receptors that are ATP-gated ion channels and G protein-coupled P2Y1,2,4,6,11,12,13 and 14 receptors for extracellular ATP, ADP, UTP, UDP and/or UDP-glucose. Recent studies have implicated specific P2Y receptor subtypes in numerous oncogenic processes, including cancer tumorigenesis, metastasis and chemotherapeutic drug resistance, where G protein-mediated signaling cascades modulate intracellular ion concentrations and activate downstream protein kinases, Src family kinases as well as numerous mitogen-activated protein kinases. We are honored to contribute to this special issue dedicated to the founder of the field of purinergic signaling, Dr. Geoffrey Burnstock, by reviewing the diverse roles of P2Y receptors in the initiation, progression and metastasis of specific cancers with an emphasis on pharmacological and genetic strategies employed to delineate cell-specific and P2Y receptor subtype-specific responses that have been investigated using in vitro and in vivo cancer models. We further highlight bioinformatic and empirical evidence on P2Y receptor expression in human clinical specimens and cover clinical perspectives where P2Y receptor-targeting interventions may have therapeutic relevance to cancer treatment.

Keywords:  Cancer; Extracellular Nucleotides; Metastasis; P2Y Receptors; Proliferation; Purinergic Receptors

DOI:  https://doi.org/10.1016/j.bcp.2021.114406
Front Pharmacol. 2020 ;11 609849

Evidence for a Cross-Talk Between Cytosolic 5'-Nucleotidases and AMP-Activated Protein Kinase.

Marcella Camici, Mercedes Garcia-Gil, Simone Allegrini, Rossana Pesi, Maria Grazia Tozzi.



Keywords:  AMP-activated kinase; body weight; cytosolic 5′-nucleotidases I and II; muscle contraction; purine cycle

DOI:  https://doi.org/10.3389/fphar.2020.609849
Anticancer Res. 2021 Jan;41(1): 137-149

MTT Test and Time-lapse Microscopy to Evaluate the Antitumor Potential of Nucleoside Analogues.

Alexandra Kiss, ViktÓria Baksa, MiklÓs Bege, LÁszlÓ TÁlas, AnikÓ BorbÁs, Ilona Bereczki, GÁspÁr BÁnfalvi, GÁbor SzemÁn-Nagy.

   BACKGROUND/AIM: Conventional viability tests, help to screen the cellular effects of candidate molecules, but the endpoint of these measurements lacks sufficient information regarding the molecular aspects. A non-invasive, easy-to-setup live-cell microscopic method served to in-depth analysis of mechanisms of potential anticancer drugs.
MATERIALS AND METHODS: The proposed method combining the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test with time-lapse scanning microscopy (TLS), provided additional data related to the cell-cycle and the dynamic properties of cell morphology. Apoptotic and necrotic events became detectable with these methods.
RESULTS: Quantification of the results was assisted by image analysis of the acquired image sequences. After demonstrating the potential of the TLS method, a series of experiments compared the in vitro effect of a known and a newly synthesized nucleoside analogue.
CONCLUSION: The proposed approach provided a more in-depth insight into the cellular processes that can be affected by known chemotherapeutic agents including nucleoside analogues rather than applying repeated individual treatments.

Keywords:  Antimetabolites; cellular morphology; nucleoside analogues; time-lapse microscopy

DOI:  https://doi.org/10.21873/anticanres.14759