Alteration of ADP-ribosylation in aging rat brain astrocytes

DNA damage and the enzyme poly(ADP-ribose)polymerase(PARP)associated with the pathogenesis of numerous age-related neurodegenerative disorders.Astrocytes play crucial roles in both support metabolic functions and cell viability of the brain.PARP regulates DNA damage and repair in the brain cells.In this study PARP activity and DNA strand break were investigated in the astrocytes isolated from young and aged rat brain.Three and 30-month-old rats were killed by decapitation and brains were removed onto an ice cooled glass plate.Astrocytes were isolated by sucrose density gradient centrifugation and glutamine synthetase(GS)served as a marker of the astrocytes lineage.The specific activity of PARP was assayed in permeabilized cells by measuring the incorporation of the ADP-ribose moiety of[3H]NAD into the nuclear acceptor proteins.The rate of DNA strand breaks was determined using a fluorescent dye and monitored spectrofluorimetry.An increase(about 75%)in the PARP activity was observed in the whole homogenates of aged rats,whereas this rise was more pronounced(about 360%)when the reaction was measured in the purified astrocyte preparations.The amount of DNA strand breaks was also higher in the astrocytes isolated from the aged brain as compared to that of young levels.The close relationship between the level of DNA strand breaks and PARP activity in the astrocytes suggest that these cells are susceptible to the metabolic alterations in aging.It is concluded that the astrocytes PARP might be considered as a therapeutic target for combating age related neurodegenerative disorders.

Poly(ADP-ribosyl)ation of Apoptosis Antagonizing Transcription Factor Involved in Hydroquinone-Induced DNA Damage Response

The molecular mechanism of DNA damage induced by hydroquinone （HQ） remains unclear. Poly（ADP-ribose） polymerase-1 （PARP-1） usually works as a DNA damage sensor, and hence, it is possible that PARP-1 is involved in the DNA damage response induced by HQ. In TK6 cells treated with HQ, PARP activity as well as the expression of apoptosis antagonizing transcription factor （AATF）, PARP-1, and phosphorylated H2AX （v-H2AX） were maximum at 0.5 h, 6 h, 3 h, and 3 h, respectively. To explore the detailed mechanisms underlying the prompt DNA repair reaction, the above indicators were investigated in PARP-l-silenced cells. PARP activity and expression of AATF and PARP-1 decreased to 36%, 32%, and 33%, respectively, in the cells; however, y-H2AX expression increased to 265%. Co-immunoprecipitation （co-IP） assays were employed to determine whether PARP-1 and AATF formed protein complexes. The interaction between these proteins together with the results from IP assays and confocal microscopy indicated that poly（ADP-ribosyl）ation {PARylation） regulated AATF expression, in conclusion, PARP-1 was involved in the DNA damage repair induced by HQ via increasing the accumulation of AATF through PARylation.

ADPRT-MEDIATED DECREASE OF CELLULAR NAD CONTENT AND THE DETECTION OF CHEMICALLY INDUCED DNA DAMAGE DEVELOPMENT OF A NEW SHORT-TERM SCREENING TEST FOR MUTAGENS

It was found that the DNA-damaging agents N-methyl-N’-nitro-N-nitrosoguanidine（MNNG）,methyl-methanesulphonate（MMS）and 4-nitroquinoline-N-oxide（4NQO）could stimulate ADP-ribosyl transferase（ADPRT）activity and reduce the cellular NAD content in a dose-dependent way.The reduction of NAD after DNA damage could be partially or completelyprevented by ADPRT inhibitors,3-aminobenzamide or nicotinamide,which showed noinfluence on reduction of NAD induced by metabolic blocking agents.Therefore,a simpleand specific method to detect DNA-damaging mutagens by measuring ADPRT-mediateddecrease of cellular NAD content was explored.Using β-naphthofiavone,a mixed functionoxygenase inducer,together with induced or uninduced human amnion FL cells,it was foundthat aflatoxin B1,benzo（a）pyrene,2-acetylaminofluorene,9,10-dimethylanthracene andethylcarbamate could induce the ADPRT-mediated decrease of cellular NAD content,while4-acetylaminofluorene,anthracene,isopropyl-N-（3-chlorophenyl）-carbamate,β-propiolactone,γ-butyrolactone,cyclophosphamide and safrol could not.The results indicate that this isa cheap and specific method to detect DNA damage caused by chemical carcinogens/mutagenswith a spccificity approaching that of the unscheduled DNA synthesis assay.

Coordinated regulation of plant immunity by poly(ADP-ribosyl)ation and K63-linked ubiquitination

Poly(ADP-ribosyl)ation(PARylation)is a posttranslational modification reversibly catalyzed by poly(ADP-ribose)polymerases(PARPs)and poly(ADP-ribose)glycohydrolases(PARGs)and plays a key role in multi-ple cellular processes.The molecular mechanisms by which PARylation regulates innate immunity remain largely unknown in eukaryotes.Here we show that Arabidopsis UBC13A and UBC13B,the major drivers of lysine 63(K63)-linked polyubiquitination,directly interact with PARPs/PARGs.Activation of pathogen-associated molecular pattern(PAMP)-triggered immunity promotes these interactions and enhances PARylation of UBC13.Both parp1 parp2 and ubc13a ubc13b mutants are compromised in immune responses with increased accumulation of total pathogenesis-related(PR)proteins but decreased accu-mulation of secreted PR proteins.Protein disulfide-isomerases(PDIs),essential components of endo-plasmic reticulum quality control(ERQC)that ensure proper folding and maturation of proteins destined for secretion,complex with PARPs/PARGs and are PARylated upon PAMP perception.Significantly,PARylation of UBC13 regulates K63-linked ubiquitination of PDIs,which may further promote their disulfide isomerase activities for correct protein folding and subsequent secretion.Taken together,these results indicate that plant immunity is coordinately regulated by PARylation and K63-linked ubiquitination.

Functions of PARylation in DNA Damage Repair Pathways

Protein poly ADP-ribosylation（PARylation） is a widespread post-translational modification at DNA lesions,which is catalyzed by poly（ADP-ribose） polymerases（PARPs）.This modification regulates a number of biological processes including chromatin reorganization,DNA damage response（DDR）,transcriptional regulation,apoptosis,and mitosis.PARP1,functioning as a DNA damage sensor,can be activated by DNA lesions,forming PAR chains that serve as a docking platform for DNA repair factors with high biochemical complexity.Here,we highlight molecular insights into PARylation recognition,the expanding role of PARylation in DDR pathways,and the functional interaction between PARylation and ubiquitination,which will offer us a better understanding of the biological roles of this unique post-translational modification.

Discovery of ARF1-targeting inhibitor demethylzeylasteral as a potential agent against breast cancer

To the Editor:ADP-ribosylation factor 1 (ARF1) plays a critical role in regulating vesicle formation and transport1. The dysregulation of ARF1 expression and/or activity is involved in many human cancers, such as breast cancer2,3. Therefore, ARF1 is one of the promising therapeutic targets for cancer treatment.

Key molecules of Mucorales for COVID-19-associated mucormycosis:a narrative review

Mucormycosis is a lethal human disease caused by fungi of the order Mucorales.Mucormycosis is caused by fungi mainly belonging to the genera Mucor,Rhizopus,and Lichtheimia,all of which belong to the order Mucorales.The number of individuals with mucormycosis-causing disorders has increased in recent years,hence,leading to the spread of mucormycosis.Throughout the coronavirus disease 2019(COVID-19)pandemic,numerous cases of mucormycosis in COVID-19-infected patients have been reported worldwide,and the illness is now recognized as COVID-19-associated mucormycosis,with most of the cases being reported from India.Immunocompromised patients such as those with bone marrow sickness and uncontrolled diabetes are at a greater risk of developing mucormycosis.Genes,pathways,and other mechanisms have been studied in Mucorales,demonstrating a direct link between virulence and prospective therapeutic and diagnostic targets.This review discusses several proteins such as high-affinity iron permease(FTR1),calcineurin,spore coat protein(CotH),and ADP-ribosylation factors involved in the pathogenesis of mucormycosis that might prove to be viable target(s)for the development of novel diagnostic and therapeutic methods.

Progress in studies on the DEK protein and its involvement in cellular apoptosis

DEK protein is an ubiquitous phosphorylated nuclear protein.Specific binding of DEK to DNA could change the topology of DNA and then affect the gene activity of the underlying DNA sequences.It is speculated that there might be some potential relationship between the stress reaction of cells and DEK proteins.The phosphorylation status of DEK protein is altered during death-receptor-mediated cell apoptosis.Both phosphorylation and poly(ADP-ribosyl)ation could promote the release of DEK from apoptotic nuclei to extracellular environment,and in this case DEK becomes a potential autoantigen of some autoimmune diseases.The available evidence powerfully suggests that DEK protein is closely relevant to apoptosis.The overexpression of DEK protein has dual function in cell apoptosis,in terms of inhibiting or triggering cell apoptosis.