The adsorption dynamics of double-stranded DNA(dsDNA)molecules on a graphene oxide(GO)surface are important for applications of DNA/GO functional structures in biosensors,biomedicine and materials science.In this work...The adsorption dynamics of double-stranded DNA(dsDNA)molecules on a graphene oxide(GO)surface are important for applications of DNA/GO functional structures in biosensors,biomedicine and materials science.In this work,molecular dynamics simulations were used to examine the adsorption of different length dsDNA molecules(from 4 bp to24 bp)on the GO surface.The dsDNA molecules could be adsorbed on the GO surface through the terminal bases and stand on the GO surface.For short dsDNA(4 bp)molecules,the double-helix structure was partially or totally broken and the adsorption dynamics was affected by the structural fluctuation of short dsDNA and the distribution of the oxidized groups on the GO surface.For long dsDNA molecules(from 8 bp to 24 bp)adsorption is stable.By nonlinear fitting of the contact angle between the axis of the dsDNA molecule and the GO surface,we found that a dsDNA molecule adsorbed on a GO surface has the chance of orienting parallel to the GO surface if the length of the dsDNA molecule is longer than 54 bp.We attributed this behavior to the flexibility of dsDNA molecules.With increasing length,the flexibility of dsDNA molecules also increases,and this increasing flexibility gives an adsorbed dsDNA molecule more chance of reaching the GO surface with the free terminal.This work provides a whole picture of adsorption of dsDNA molecules on the GO surface and should be of benefit for the design of DNA/GO based biosensors.展开更多
In our previous study, complete single DNA strands which were obtained from nuclei, chloroplasts and plant mitochondria obeyed Chargaff’s second parity rule, although those which were obtained from animal mitochondri...In our previous study, complete single DNA strands which were obtained from nuclei, chloroplasts and plant mitochondria obeyed Chargaff’s second parity rule, although those which were obtained from animal mitochondria deviated from the rule. On the other hand, plant mitochondria obeyed another different rule after their classification. Complete single DNA strand sequences obtained from chloroplasts, plant mitochondria, and animal mitochondria, were divided into the coding and non-coding regions. The non-coding region, which was the complementary coding region on the reverse strand, was incorporated as a coding region in the forward strand. When the nucleotide contents of the coding region or non-coding regions were plotted against the composition of the four nucleotides in the complete single DNA strand, it was determined that chloroplast and plant mitochondrial DNA obeyed Chargaff’s second parity rule in both the coding and non-coding regions. However, animal mitochondrial DNA deviated from this rule. In chloroplast and plant mitochondrial DNA, which obey Chargaff’s second parity rule, the lines of regression for G (purine) and C (pyrimidine) intersected with regression lines for A (purine) and T (pyrimidines), respectively, at around 0.250 in all cases. On the other hand, in animal mitochondrial DNA, which deviates from Chargaff’s second parity rule, only regression lines due to the content of homonucleotides or their analogs in the coding or non-coding region against those in the complete single DNA strand intersected at around 0.250 at the horizontal axis. Conversely, the intersection of the two lines of regression (G and A or C and T) against the contents of heteronucleotides or their analogs shifted from 0.25 in both coding and non-coding regions. Nucleotide alternations in chloroplasts and plant mitochondria are strictly regulated, not only by the proportion of homonucleotides and their analogs, but also by the heteronucleotides and their analogs. They are strictly regulated in animal mitochondria only by the content of homonucleotides and their analogs.展开更多
Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chro...Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chromosomes together until the metaphase I to anaphase I transition, is critical for proper chromosome segregation. Recent studies have suggested that the SPO 11 proteins have conserved functions in a number of organisms in generating sites of double-stranded DNA breaks （DSBs） that are thought to be the starting points of homologous recombination. Processing of these sites of DSBs requires the function of RecA homologs, such as RAD5 1, DMC 1, and others, as suggested by mutant studies; thus the failure to repair these meiotic DSBs results in abnormal chromosomal alternations, leading to disrupted meiosis. Recent discoveries on the functions of these RecA homologs have improved the understanding of the mechanisms underlying meiotic homologous recombination.展开更多
In microcantilever-based label-free biodetection technologies, deflection changes induced by adsorptions of double-stranded DNA （dsDNA） molecules on Au-layer surface are greatly affected by the mechanical, thermal a...In microcantilever-based label-free biodetection technologies, deflection changes induced by adsorptions of double-stranded DNA （dsDNA） molecules on Au-layer surface are greatly affected by the mechanical, thermal and electrical properties of DNA biofilm. In this paper, the elastic properties of dsDNA biofilm are studied. First, the Parsegian＇s empirical potential based on a mesoscopic liq- uid crystal theory is employed to describe the interaction energy among coarse-grained DNA cylinders. Then, con- sidering a Gaussian distribution of DNA interaxial distance, the thought experiment method is used to derive an analyti- cal expression for Young＇s modulus of DNA biofilm with a stochastic packing pattern for the first time. Results show that Young＇s modulus of DNA biofilm is on the order of 10 MPa. These findings could provide a simple and effective method to evaluate the mechanical properties of soft biofilm on snbstrate.展开更多
Hepatitis B virus(HBV)-induced hepatocellular carcinoma(HCC) is one of the most fre-quently occurring cancers.Hepadnaviral DNA integrations are considered to be essential agents which can promote the process of the he...Hepatitis B virus(HBV)-induced hepatocellular carcinoma(HCC) is one of the most fre-quently occurring cancers.Hepadnaviral DNA integrations are considered to be essential agents which can promote the process of the hepatocarcinogenesis.More and more researches were designed to find the relationship of the two.In this study,we investigated whether HBV DNA integration occurred at sites of DNA double-strand breaks(DSBs),one of the most detrimental DNA damage.An 18-bp I-SceI homing endonuclease recognition site was introduced into the DNA of HepG2 cell line by stable DNA transfection,then cells were incubated in patients’ serum with high HBV DNA copies and at the same time,DSBs were induced by transient expression of I-SceI after transfection of an I-SceI expression vector.By using nest PCR,the viral DNA was detected at the sites of the break.It appeared that integra-tion occurred between part of HBV x gene and the I-SceI induced breaks.The results suggested that DSBs,as the DNA damages,may serve as potential targets for hepadnaviral DNA insertion and the integrants would lead to widespread host genome changes necessarily.It provided a new site to investi-gate the integration.展开更多
DNA damage in oocytes can cause infertility and birth defects. DNA double-strand breaks （DSBs） are highly deleterious and can substantially impair genome integrity. Homologous recombination （HR）-mediated DNA DSB r...DNA damage in oocytes can cause infertility and birth defects. DNA double-strand breaks （DSBs） are highly deleterious and can substantially impair genome integrity. Homologous recombination （HR）-mediated DNA DSB repair plays dominant roles in safeguarding oocyte quantity and quality. However, little is known regarding the key players of the HR repair pathway in oocytes. Here, we identified oocyte-specific gene Ooep as a novel key component of the HR repair pathway in mouse oocytes. OOEP was required for efficient ataxia telangiectasia mutated （ATM） kinase activation and Rad51 recombinase （RAD51） focal accumulation at DNA DSBs. Ooep null oocytes were defective in DNA DSB repair and prone to apoptosis upon exogenous DNA damage insults. Moreover, Ooep null oocytes exhibited delayed meiotic maturation. Therefore, OOEP played roles in preserving oocyte quantity and quality by maintaining genome stability. Ooep expression decreased with the advance of maternal age, suggesting its involvement in maternal aging.展开更多
The purpose of the study was to investigate if the high gradient strength and slew rate used for long MRI-thermometry monitoring could cause DNA double-stranded breaks (DSBs). To this end, an enzyme-linked immunosorbe...The purpose of the study was to investigate if the high gradient strength and slew rate used for long MRI-thermometry monitoring could cause DNA double-stranded breaks (DSBs). To this end, an enzyme-linked immunosorbent assay (ELISA) was used to quantify γH2AX, a molecular marker for DSBs, in the blood of mice after a 6-hour exposure to magnetic resonance imaging (MRI). Fourteen CF-1 female mice were separated into 4 experimental groups: Untreated negative control, MRI-treated, MRI-Control, and exposed to ionizing radiation positive control. Untreated negative control was used as a baseline for ELISA to quantify γH2AX. MRI-treated consisted of a 6-hour continuous magnetic resonance imaging (MRI) echo planar imaging (EPI) sequence with a slew rate of 192 mT/m/s constituting a significantly longer imaging time than routine clinical imaging. MRI-control mice were maintained under the same conditions outside the MRI scanner for 6-hours. Mice in the irradiation group served as a positive control of DSBs and were exposed to either 2 Gy, 5 Gy or 10 Gy of ionizing radiation. DSBs in the blood lymphocytes from the treatment groups were analyzed using the γH2AX ELISA and compared. Total protein concentration in lysates was determined for each blood sample and averaged 1 ± 0.35 mg/mL. Irradiated positive controls were used to test radiation dose-dependency of the γH2AX ELISA assay where a linear dependency on radiation exposure was observed (r<sup>2</sup> = 0.93) between untreated and irradiated samples. Mean and standard error mean of γH2AX formation were calculated and compared between each treatment group. Repeated measures 1-way ANOVA showed statistically significant differences between the means of irradiated controls and both the MRI-control and MRI-treated groups. There was no statistically significant difference between the MRI-treated samples and the MRI-control groups. Our results show that long MRI exposure at a high slew rate did not cause increased levels of γH2AX when compared to control mice, suggesting that no increase in DSBs was caused by the long MR thermometry imaging session. The novelty of this work contradicts other studies that have suggested MRI may cause DSBs;this work suggests an alternative cause of DNA damage.展开更多
BACKGROUND Poly(ADP-ribose)polymerase inhibitors(PARPis)are approved as first-line therapies for breast cancer gene(BRCA)-positive,human epidermal growth factor receptor 2-negative locally advanced or metastatic breas...BACKGROUND Poly(ADP-ribose)polymerase inhibitors(PARPis)are approved as first-line therapies for breast cancer gene(BRCA)-positive,human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer.They are also effective for new and recurrent ovarian cancers that are BRCA-or homologous recombination deficiency(HRD)-positive.However,data on these mutations and PARPi use in the Middle East are limited.AIM To assess BRCA/HRD prevalence and PARPi use in patients in the Middle East with breast/ovarian cancer.METHODS This was a single-center retrospective study of 57 of 472 breast cancer patients tested for BRCA mutations,and 25 of 65 ovarian cancer patients tested for HRD.These adult patients participated in at least four visits to the oncology service at our center between August 2021 and May 2023.Data were summarized using descriptive statistics and compared using counts and percentages.Response to treatment was assessed using Response Evaluation Criteria in Solid Tumors criteria.RESULTS Among the 472 breast cancer patients,12.1%underwent BRCA testing,and 38.5%of 65 ovarian cancer patients received HRD testing.Pathogenic mutations were found in 25.6%of the tested patients:26.3%breast cancers had germline BRCA(gBRCA)mutations and 24.0%ovarian cancers showed HRD.Notably,40.0%of gBRCA-positive breast cancers and 66.0%of HRD-positive ovarian cancers were Middle Eastern and Asian patients,respectively.PARPi treatment was used in 5(33.3%)gBRCA-positive breast cancer patients as first-line therapy(n=1;7-months progression-free),for maintenance(n=2;>15-months progression-free),or at later stages due to compliance issues(n=2).Four patients(66.6%)with HRD-positive ovarian cancer received PARPi and all remained progression-free.CONCLUSION Lower testing rates but higher BRCA mutations in breast cancer were found.Ethnicity reflected United Arab Emirates demographics,with breast cancer in Middle Eastern and ovarian cancer in Asian patients.展开更多
Homologous recombination （HR） comprises a series of interrelated pathways that function in the repair of DNA double-stranded breaks （DSBs） and interstrand crosslinks （ICLs）. In addition, recombination provides c...Homologous recombination （HR） comprises a series of interrelated pathways that function in the repair of DNA double-stranded breaks （DSBs） and interstrand crosslinks （ICLs）. In addition, recombination provides critical support for DNA replication in the recovery of stalled or broken replication forks, contributing to tolerance of DNA damage. A central core of proteins, most critically the RecA homolog Rad51, catalyzes the key reactions that typify HR： homology search and DNA strand invasion. The diverse functions of recombination are reflected in the need for context-specific factors that perform supplemental functions in conjunction with the core proteins. The inability to properly repair complex DNA damage and resolve DNA replication stress leads to genomic instability and contributes to cancer etiology. Mutations in the BRCA2 recombination gene cause predisposition to breast and ovarian cancer as well as Fanconi anemia, a cancer predisposition syndrome characterized by a defect in the repair of DNA interstrand crosslinks. The cellular functions of recombination are also germane to DNA-based treatment modalities of cancer, which target replicating cells by the direct or indirect induction of DNA lesions that are substrates for recombination pathways. This review focuses on mechanistic aspects of HR relating to DSB and ICL repair as well as replication fork support.展开更多
The major histocompatibility complex(MHC) is the exclusive chaperone that presents intracellular antigens,either self or foreign to T cells.Interestingly,aberrant expression of MHC molecules has been reported in vario...The major histocompatibility complex(MHC) is the exclusive chaperone that presents intracellular antigens,either self or foreign to T cells.Interestingly,aberrant expression of MHC molecules has been reported in various autoimmune target tissues such as thyroid follicular cells in Grave's disease.Herein,we review the discovery of an unexpected effect of cytosolic doublestranded DNA(ds DNA),despite its origins,to induce antigen processing and presenting genes,including MHC molecules,in non-immune cells.Moreover,we highlight several recent studies that suggest cell injury endows thyroid epithelial cells with a phenotype of mature antigen presenting cells by inducing multiple antigen processing and presenting genes via releasing genomic DNA fragments into the cytosol.We discuss the possibility that such cytosolic ds DNA,in naked form without binding to histone proteins,might be involved in the development of cell damage-triggered autoimmune responses.We also discuss the possible molecular mechanism by which cytosolic ds DNA can induce MHC molecules.It is reasonable to speculate that cytosolic ds DNA-induced MHC class Ⅰ is partially due to an autocrine/paracrine effect of type Ⅰ interferon(IFN).While the mechanism of cytosolic ds DNA-induced MHC class Ⅱ expression appears,at least partially,distinct from that mediated by IFN-γ.Further in-depth are required to clarify this picture.展开更多
Objective To explore if strand breaks of DNA in human early chorionic villus cells in uterus were induced by diagnostic ultrasound and to evaluate the method used for detection of single-stranded breaks and double-str...Objective To explore if strand breaks of DNA in human early chorionic villus cells in uterus were induced by diagnostic ultrasound and to evaluate the method used for detection of single-stranded breaks and double-stranded breaks in human DNA. Methods 60 normal pregnant women aged 20-30, who underwent artificial abortion during 6-8 weeks of gestation, were randomly divided into 2 experimental groups: All 30 cases were exposed to diagnostic ultrasound in uterus for 10 minutes, and 24 hours later chorionic villi were extracted; the other 30 cases were taken as the control group. Single-stranded DNA and double-stranded DNA in villus cells in all cases were isolated by the alkaline unwinding combined with hydroxylapatite chromatography, and were quantitatively detected using 32 P-labeled Alu probe for dot-blotting hybridization. Results There was no significant difference in quantity and percentage in single-stranded DNA and double-stranded DNA between 2 groups (P>0.05). 32 P-Alu probe could only hybridize with human DNA, and could detect DNA isolated from as few as 2.5×10 3 chorionic villus cells and 0.45ng DNA in human leukocytes. Conclusion The results suggested that there were no DNA strand damages in human chorionic villus cells when the uterus was exposed to diagnostic ultrasound for 10 minutes. The method,^(32)P-Alu probe for dot-blotting hybridization, was even more specific, sensitive and accurate than conventional approaches.展开更多
DNA double-stranded break(DSB)is one of the most catastrophic damages of genotoxic insult.Inappropriate repair of DNA DSBs results in the loss of genetic information,mutation,and the generation of harmful genomic rear...DNA double-stranded break(DSB)is one of the most catastrophic damages of genotoxic insult.Inappropriate repair of DNA DSBs results in the loss of genetic information,mutation,and the generation of harmful genomic rearrangements,which predisposes an organism to immunodeficiency,neurological damage,and cancer.The tumor repressor p53 plays a key role in DNA damage response,and has been found to be mutated in 50%of human cancer.p53,p63,and p73 are three members of the p53 gene family.Recent discoveries have shown that human p53 gene encodes at least 12 isoforms.Different p53 members and isoforms play various roles in orchestrating DNA damage response to maintain genomic integrity.This review briefly explores the functions of p53 and its isoforms in DNA DSB repair.展开更多
Accumulating evidence indicates that ataxia-telangiectasia mutated kinase is critical for maintaining cellular homeostasis and that it has both nuclear and cytoplasmic functions.However,the functions of ataxia-telangi...Accumulating evidence indicates that ataxia-telangiectasia mutated kinase is critical for maintaining cellular homeostasis and that it has both nuclear and cytoplasmic functions.However,the functions of ataxia-telangiectasia mutated that when lost lead to cerebellar degeneration are still unknown.In this review,we first describe the role of ataxia-telangiectasia mutated in cerebellar pathology.In addition to its canonical nuclear functions in DNA damage response circuits,ataxia-telangiectasia mutated functions in various cytoplasmic and mitochondrial processes that are critically important for cellular homeostasis.We discuss these functions with a focus on the role of ataxia-telangiectasia mutated in maintaining the homeostatic redox state.Finally,we describe the unique functions of ataxia-telangiectasia mutated in various types of neuronal and glial cells including cerebellar granule neurons,astrocytes,and microglial cells.展开更多
The interaction of double-stranded （ds） and G-quadruplex （G4） DNA with sulfonyl 5-fluorouracil derivatives （5-fluoro-l-（arylsulfonyl） pyrimidine-2,4 （1H,3H）-diones） was investigated in this research, in whic...The interaction of double-stranded （ds） and G-quadruplex （G4） DNA with sulfonyl 5-fluorouracil derivatives （5-fluoro-l-（arylsulfonyl） pyrimidine-2,4 （1H,3H）-diones） was investigated in this research, in which Au electrodes modified with ds-DNA or G4-DNAs were used as a working electrode. The investigation showed that the binding affinity with G4-DNA was significantly increased when 5-fluorouracil （5-FU） was modified with arylsulfonyl groups. The presence of strong electron-withdrawing groups on benzene sulfonyl 5-FU greatly enhanced the binding selectivity （kG4-DNA/kds-DNA）. Such results provided new insights into the potential connections between the chemical structure of drug candidates and their anticancer activities.展开更多
The hematopoietic system is susceptible to ionizing radiation(IR),which can cause acute hematopoietic failure or long-term myelosuppression.As the most primitive cells of the hematopoietic hierarchy,hematopoietic stem...The hematopoietic system is susceptible to ionizing radiation(IR),which can cause acute hematopoietic failure or long-term myelosuppression.As the most primitive cells of the hematopoietic hierarchy,hematopoietic stem cells(HSCs)maintain lifelong hematopoietic homeostasis and promote hematopoietic regeneration during stress.Numerous studies have shown that nuclear and mitochondrial genomes are the main targets of radiation injury in HSCs.More importantly,the damage of DNA may trigger a series of biological responses that largely determine HSC fate following IR exposure.Although some essential pathways and factors involved in DNA injury and damage in HSCs have been revealed,a comprehensive understanding of the biological effects of radiation on HSCs still needs to be improved.This review focuses on recent insights into the molecular mechanisms underlying DNA damage and repair in HSCs after IR.Then summarize corresponding regulatory measures,which may provide a reference for further research in this field.展开更多
The site-specific mutagenesis of the gene has become an important technique in gene modification and protein engineering. Among all methods, the primer extension one using single-stranded DNA (such as the infective fo...The site-specific mutagenesis of the gene has become an important technique in gene modification and protein engineering. Among all methods, the primer extension one using single-stranded DNA (such as the infective form of the M13 phage ) as template and the gapped stranded one are commonly used. But some genes, especially those展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.11974366)the Fundamental Research Funds for the Central Universities+2 种基金Chinathe Supercomputer Center of the Chinese Academy of Sciencesthe Shanghai Supercomputer Center of China。
文摘The adsorption dynamics of double-stranded DNA(dsDNA)molecules on a graphene oxide(GO)surface are important for applications of DNA/GO functional structures in biosensors,biomedicine and materials science.In this work,molecular dynamics simulations were used to examine the adsorption of different length dsDNA molecules(from 4 bp to24 bp)on the GO surface.The dsDNA molecules could be adsorbed on the GO surface through the terminal bases and stand on the GO surface.For short dsDNA(4 bp)molecules,the double-helix structure was partially or totally broken and the adsorption dynamics was affected by the structural fluctuation of short dsDNA and the distribution of the oxidized groups on the GO surface.For long dsDNA molecules(from 8 bp to 24 bp)adsorption is stable.By nonlinear fitting of the contact angle between the axis of the dsDNA molecule and the GO surface,we found that a dsDNA molecule adsorbed on a GO surface has the chance of orienting parallel to the GO surface if the length of the dsDNA molecule is longer than 54 bp.We attributed this behavior to the flexibility of dsDNA molecules.With increasing length,the flexibility of dsDNA molecules also increases,and this increasing flexibility gives an adsorbed dsDNA molecule more chance of reaching the GO surface with the free terminal.This work provides a whole picture of adsorption of dsDNA molecules on the GO surface and should be of benefit for the design of DNA/GO based biosensors.
文摘In our previous study, complete single DNA strands which were obtained from nuclei, chloroplasts and plant mitochondria obeyed Chargaff’s second parity rule, although those which were obtained from animal mitochondria deviated from the rule. On the other hand, plant mitochondria obeyed another different rule after their classification. Complete single DNA strand sequences obtained from chloroplasts, plant mitochondria, and animal mitochondria, were divided into the coding and non-coding regions. The non-coding region, which was the complementary coding region on the reverse strand, was incorporated as a coding region in the forward strand. When the nucleotide contents of the coding region or non-coding regions were plotted against the composition of the four nucleotides in the complete single DNA strand, it was determined that chloroplast and plant mitochondrial DNA obeyed Chargaff’s second parity rule in both the coding and non-coding regions. However, animal mitochondrial DNA deviated from this rule. In chloroplast and plant mitochondrial DNA, which obey Chargaff’s second parity rule, the lines of regression for G (purine) and C (pyrimidine) intersected with regression lines for A (purine) and T (pyrimidines), respectively, at around 0.250 in all cases. On the other hand, in animal mitochondrial DNA, which deviates from Chargaff’s second parity rule, only regression lines due to the content of homonucleotides or their analogs in the coding or non-coding region against those in the complete single DNA strand intersected at around 0.250 at the horizontal axis. Conversely, the intersection of the two lines of regression (G and A or C and T) against the contents of heteronucleotides or their analogs shifted from 0.25 in both coding and non-coding regions. Nucleotide alternations in chloroplasts and plant mitochondria are strictly regulated, not only by the proportion of homonucleotides and their analogs, but also by the heteronucleotides and their analogs. They are strictly regulated in animal mitochondria only by the content of homonucleotides and their analogs.
基金The authors thank Alexandra Surcel and Carey L Hendrix Lord for helpful comments on this manuscript.The work in our laboratory is supported by grants from the National Science Foundation(IBN-0077832,MCB-9896340,MCB-0092075)the National Institutes of Health(R0 1 GM63871)+3 种基金the US Department of Agriculture(2001-35301-10570 and 2003-35301-13313)Wuxing L was partially supported by the Intercollege Graduate Degree Program in Plant PhysiologyHong M gratefully acknowledges the support of the John Simon Guggenheim Foundationthe National Institutes of Health(F33 GM72245-1).
文摘Meiotic prophase I is a long and complex phase. Homologous recombination is an important process that occurs between homologous chromosomes during meiotic prophase I. Formation of chiasmata, which hold homologous chromosomes together until the metaphase I to anaphase I transition, is critical for proper chromosome segregation. Recent studies have suggested that the SPO 11 proteins have conserved functions in a number of organisms in generating sites of double-stranded DNA breaks （DSBs） that are thought to be the starting points of homologous recombination. Processing of these sites of DSBs requires the function of RecA homologs, such as RAD5 1, DMC 1, and others, as suggested by mutant studies; thus the failure to repair these meiotic DSBs results in abnormal chromosomal alternations, leading to disrupted meiosis. Recent discoveries on the functions of these RecA homologs have improved the understanding of the mechanisms underlying meiotic homologous recombination.
基金supported by the National Natural Science Foundation of China(11272193 and 10872121)the Shanghai Leading Academic Discipline Project(S30106)
文摘In microcantilever-based label-free biodetection technologies, deflection changes induced by adsorptions of double-stranded DNA （dsDNA） molecules on Au-layer surface are greatly affected by the mechanical, thermal and electrical properties of DNA biofilm. In this paper, the elastic properties of dsDNA biofilm are studied. First, the Parsegian＇s empirical potential based on a mesoscopic liq- uid crystal theory is employed to describe the interaction energy among coarse-grained DNA cylinders. Then, con- sidering a Gaussian distribution of DNA interaxial distance, the thought experiment method is used to derive an analyti- cal expression for Young＇s modulus of DNA biofilm with a stochastic packing pattern for the first time. Results show that Young＇s modulus of DNA biofilm is on the order of 10 MPa. These findings could provide a simple and effective method to evaluate the mechanical properties of soft biofilm on snbstrate.
基金supported by grants from National Natural Sciences Foundation of China (No.30872237)the National Basic Research Program of China(No.2007CB512900)
文摘Hepatitis B virus(HBV)-induced hepatocellular carcinoma(HCC) is one of the most fre-quently occurring cancers.Hepadnaviral DNA integrations are considered to be essential agents which can promote the process of the hepatocarcinogenesis.More and more researches were designed to find the relationship of the two.In this study,we investigated whether HBV DNA integration occurred at sites of DNA double-strand breaks(DSBs),one of the most detrimental DNA damage.An 18-bp I-SceI homing endonuclease recognition site was introduced into the DNA of HepG2 cell line by stable DNA transfection,then cells were incubated in patients’ serum with high HBV DNA copies and at the same time,DSBs were induced by transient expression of I-SceI after transfection of an I-SceI expression vector.By using nest PCR,the viral DNA was detected at the sites of the break.It appeared that integra-tion occurred between part of HBV x gene and the I-SceI induced breaks.The results suggested that DSBs,as the DNA damages,may serve as potential targets for hepadnaviral DNA insertion and the integrants would lead to widespread host genome changes necessarily.It provided a new site to investi-gate the integration.
基金supported by the National Key Research and Development Program of China(2017YFC1001102)National Natural Science Foundation of China(81760507)
文摘DNA damage in oocytes can cause infertility and birth defects. DNA double-strand breaks （DSBs） are highly deleterious and can substantially impair genome integrity. Homologous recombination （HR）-mediated DNA DSB repair plays dominant roles in safeguarding oocyte quantity and quality. However, little is known regarding the key players of the HR repair pathway in oocytes. Here, we identified oocyte-specific gene Ooep as a novel key component of the HR repair pathway in mouse oocytes. OOEP was required for efficient ataxia telangiectasia mutated （ATM） kinase activation and Rad51 recombinase （RAD51） focal accumulation at DNA DSBs. Ooep null oocytes were defective in DNA DSB repair and prone to apoptosis upon exogenous DNA damage insults. Moreover, Ooep null oocytes exhibited delayed meiotic maturation. Therefore, OOEP played roles in preserving oocyte quantity and quality by maintaining genome stability. Ooep expression decreased with the advance of maternal age, suggesting its involvement in maternal aging.
文摘The purpose of the study was to investigate if the high gradient strength and slew rate used for long MRI-thermometry monitoring could cause DNA double-stranded breaks (DSBs). To this end, an enzyme-linked immunosorbent assay (ELISA) was used to quantify γH2AX, a molecular marker for DSBs, in the blood of mice after a 6-hour exposure to magnetic resonance imaging (MRI). Fourteen CF-1 female mice were separated into 4 experimental groups: Untreated negative control, MRI-treated, MRI-Control, and exposed to ionizing radiation positive control. Untreated negative control was used as a baseline for ELISA to quantify γH2AX. MRI-treated consisted of a 6-hour continuous magnetic resonance imaging (MRI) echo planar imaging (EPI) sequence with a slew rate of 192 mT/m/s constituting a significantly longer imaging time than routine clinical imaging. MRI-control mice were maintained under the same conditions outside the MRI scanner for 6-hours. Mice in the irradiation group served as a positive control of DSBs and were exposed to either 2 Gy, 5 Gy or 10 Gy of ionizing radiation. DSBs in the blood lymphocytes from the treatment groups were analyzed using the γH2AX ELISA and compared. Total protein concentration in lysates was determined for each blood sample and averaged 1 ± 0.35 mg/mL. Irradiated positive controls were used to test radiation dose-dependency of the γH2AX ELISA assay where a linear dependency on radiation exposure was observed (r<sup>2</sup> = 0.93) between untreated and irradiated samples. Mean and standard error mean of γH2AX formation were calculated and compared between each treatment group. Repeated measures 1-way ANOVA showed statistically significant differences between the means of irradiated controls and both the MRI-control and MRI-treated groups. There was no statistically significant difference between the MRI-treated samples and the MRI-control groups. Our results show that long MRI exposure at a high slew rate did not cause increased levels of γH2AX when compared to control mice, suggesting that no increase in DSBs was caused by the long MR thermometry imaging session. The novelty of this work contradicts other studies that have suggested MRI may cause DSBs;this work suggests an alternative cause of DNA damage.
文摘BACKGROUND Poly(ADP-ribose)polymerase inhibitors(PARPis)are approved as first-line therapies for breast cancer gene(BRCA)-positive,human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer.They are also effective for new and recurrent ovarian cancers that are BRCA-or homologous recombination deficiency(HRD)-positive.However,data on these mutations and PARPi use in the Middle East are limited.AIM To assess BRCA/HRD prevalence and PARPi use in patients in the Middle East with breast/ovarian cancer.METHODS This was a single-center retrospective study of 57 of 472 breast cancer patients tested for BRCA mutations,and 25 of 65 ovarian cancer patients tested for HRD.These adult patients participated in at least four visits to the oncology service at our center between August 2021 and May 2023.Data were summarized using descriptive statistics and compared using counts and percentages.Response to treatment was assessed using Response Evaluation Criteria in Solid Tumors criteria.RESULTS Among the 472 breast cancer patients,12.1%underwent BRCA testing,and 38.5%of 65 ovarian cancer patients received HRD testing.Pathogenic mutations were found in 25.6%of the tested patients:26.3%breast cancers had germline BRCA(gBRCA)mutations and 24.0%ovarian cancers showed HRD.Notably,40.0%of gBRCA-positive breast cancers and 66.0%of HRD-positive ovarian cancers were Middle Eastern and Asian patients,respectively.PARPi treatment was used in 5(33.3%)gBRCA-positive breast cancer patients as first-line therapy(n=1;7-months progression-free),for maintenance(n=2;>15-months progression-free),or at later stages due to compliance issues(n=2).Four patients(66.6%)with HRD-positive ovarian cancer received PARPi and all remained progression-free.CONCLUSION Lower testing rates but higher BRCA mutations in breast cancer were found.Ethnicity reflected United Arab Emirates demographics,with breast cancer in Middle Eastern and ovarian cancer in Asian patients.
文摘Homologous recombination （HR） comprises a series of interrelated pathways that function in the repair of DNA double-stranded breaks （DSBs） and interstrand crosslinks （ICLs）. In addition, recombination provides critical support for DNA replication in the recovery of stalled or broken replication forks, contributing to tolerance of DNA damage. A central core of proteins, most critically the RecA homolog Rad51, catalyzes the key reactions that typify HR： homology search and DNA strand invasion. The diverse functions of recombination are reflected in the need for context-specific factors that perform supplemental functions in conjunction with the core proteins. The inability to properly repair complex DNA damage and resolve DNA replication stress leads to genomic instability and contributes to cancer etiology. Mutations in the BRCA2 recombination gene cause predisposition to breast and ovarian cancer as well as Fanconi anemia, a cancer predisposition syndrome characterized by a defect in the repair of DNA interstrand crosslinks. The cellular functions of recombination are also germane to DNA-based treatment modalities of cancer, which target replicating cells by the direct or indirect induction of DNA lesions that are substrates for recombination pathways. This review focuses on mechanistic aspects of HR relating to DSB and ICL repair as well as replication fork support.
基金Scientific Research from the Japan Society for the Promotion of Science to Suzuki K,No.15K09444
文摘The major histocompatibility complex(MHC) is the exclusive chaperone that presents intracellular antigens,either self or foreign to T cells.Interestingly,aberrant expression of MHC molecules has been reported in various autoimmune target tissues such as thyroid follicular cells in Grave's disease.Herein,we review the discovery of an unexpected effect of cytosolic doublestranded DNA(ds DNA),despite its origins,to induce antigen processing and presenting genes,including MHC molecules,in non-immune cells.Moreover,we highlight several recent studies that suggest cell injury endows thyroid epithelial cells with a phenotype of mature antigen presenting cells by inducing multiple antigen processing and presenting genes via releasing genomic DNA fragments into the cytosol.We discuss the possibility that such cytosolic ds DNA,in naked form without binding to histone proteins,might be involved in the development of cell damage-triggered autoimmune responses.We also discuss the possible molecular mechanism by which cytosolic ds DNA can induce MHC molecules.It is reasonable to speculate that cytosolic ds DNA-induced MHC class Ⅰ is partially due to an autocrine/paracrine effect of type Ⅰ interferon(IFN).While the mechanism of cytosolic ds DNA-induced MHC class Ⅱ expression appears,at least partially,distinct from that mediated by IFN-γ.Further in-depth are required to clarify this picture.
文摘Objective To explore if strand breaks of DNA in human early chorionic villus cells in uterus were induced by diagnostic ultrasound and to evaluate the method used for detection of single-stranded breaks and double-stranded breaks in human DNA. Methods 60 normal pregnant women aged 20-30, who underwent artificial abortion during 6-8 weeks of gestation, were randomly divided into 2 experimental groups: All 30 cases were exposed to diagnostic ultrasound in uterus for 10 minutes, and 24 hours later chorionic villi were extracted; the other 30 cases were taken as the control group. Single-stranded DNA and double-stranded DNA in villus cells in all cases were isolated by the alkaline unwinding combined with hydroxylapatite chromatography, and were quantitatively detected using 32 P-labeled Alu probe for dot-blotting hybridization. Results There was no significant difference in quantity and percentage in single-stranded DNA and double-stranded DNA between 2 groups (P>0.05). 32 P-Alu probe could only hybridize with human DNA, and could detect DNA isolated from as few as 2.5×10 3 chorionic villus cells and 0.45ng DNA in human leukocytes. Conclusion The results suggested that there were no DNA strand damages in human chorionic villus cells when the uterus was exposed to diagnostic ultrasound for 10 minutes. The method,^(32)P-Alu probe for dot-blotting hybridization, was even more specific, sensitive and accurate than conventional approaches.
基金supported by the National Natural Science Foundation of China(Nos.31571511 and 31871500)
文摘DNA double-stranded break(DSB)is one of the most catastrophic damages of genotoxic insult.Inappropriate repair of DNA DSBs results in the loss of genetic information,mutation,and the generation of harmful genomic rearrangements,which predisposes an organism to immunodeficiency,neurological damage,and cancer.The tumor repressor p53 plays a key role in DNA damage response,and has been found to be mutated in 50%of human cancer.p53,p63,and p73 are three members of the p53 gene family.Recent discoveries have shown that human p53 gene encodes at least 12 isoforms.Different p53 members and isoforms play various roles in orchestrating DNA damage response to maintain genomic integrity.This review briefly explores the functions of p53 and its isoforms in DNA DSB repair.
文摘Accumulating evidence indicates that ataxia-telangiectasia mutated kinase is critical for maintaining cellular homeostasis and that it has both nuclear and cytoplasmic functions.However,the functions of ataxia-telangiectasia mutated that when lost lead to cerebellar degeneration are still unknown.In this review,we first describe the role of ataxia-telangiectasia mutated in cerebellar pathology.In addition to its canonical nuclear functions in DNA damage response circuits,ataxia-telangiectasia mutated functions in various cytoplasmic and mitochondrial processes that are critically important for cellular homeostasis.We discuss these functions with a focus on the role of ataxia-telangiectasia mutated in maintaining the homeostatic redox state.Finally,we describe the unique functions of ataxia-telangiectasia mutated in various types of neuronal and glial cells including cerebellar granule neurons,astrocytes,and microglial cells.
基金supported by the National Natural Science Foundation of China (21073133,20843007)Zhejiang Provincial Natural Science Foundation of China (Y4080177,Y4090248,Y5100283)Zhejiang Provincial Ministry of Education (Y200907715)
文摘The interaction of double-stranded （ds） and G-quadruplex （G4） DNA with sulfonyl 5-fluorouracil derivatives （5-fluoro-l-（arylsulfonyl） pyrimidine-2,4 （1H,3H）-diones） was investigated in this research, in which Au electrodes modified with ds-DNA or G4-DNAs were used as a working electrode. The investigation showed that the binding affinity with G4-DNA was significantly increased when 5-fluorouracil （5-FU） was modified with arylsulfonyl groups. The presence of strong electron-withdrawing groups on benzene sulfonyl 5-FU greatly enhanced the binding selectivity （kG4-DNA/kds-DNA）. Such results provided new insights into the potential connections between the chemical structure of drug candidates and their anticancer activities.
基金supported by National Natural Science Foundation of China(No.81930090,82203974)Natural Science Foundation of Chongqing City,China(No.CSTB2023NSCQ-MSX0284)+2 种基金Postdoctoral Innovative Talent Support Program of China(No.BX20220398)China Postdoctoral Science Foundation(No.2022M723867)Postdoctoral Innovative Talent Support Program of Chongqing,(No.CQBX2021017)China.
文摘The hematopoietic system is susceptible to ionizing radiation(IR),which can cause acute hematopoietic failure or long-term myelosuppression.As the most primitive cells of the hematopoietic hierarchy,hematopoietic stem cells(HSCs)maintain lifelong hematopoietic homeostasis and promote hematopoietic regeneration during stress.Numerous studies have shown that nuclear and mitochondrial genomes are the main targets of radiation injury in HSCs.More importantly,the damage of DNA may trigger a series of biological responses that largely determine HSC fate following IR exposure.Although some essential pathways and factors involved in DNA injury and damage in HSCs have been revealed,a comprehensive understanding of the biological effects of radiation on HSCs still needs to be improved.This review focuses on recent insights into the molecular mechanisms underlying DNA damage and repair in HSCs after IR.Then summarize corresponding regulatory measures,which may provide a reference for further research in this field.
基金Project supported by the National High Technology Foundation (Term No. 103-20).
文摘The site-specific mutagenesis of the gene has become an important technique in gene modification and protein engineering. Among all methods, the primer extension one using single-stranded DNA (such as the infective form of the M13 phage ) as template and the gapped stranded one are commonly used. But some genes, especially those
