Transcription-coupled nucleotide excision repair in mammalian cells： molecular mechanisms and biological effects

The encounter of elongating RNA polymerase Ⅱ （RNAPⅡo） with DNA lesions has severe consequences for the cell as this event provides a strong signal for P53-dependent apoptosis and cell cycle arrest. To counteract prolonged blockage of transcription, the cell removes the RNAPⅡo-blocking DNA lesions by transcription-coupled repair （TC-NER）, a specialized subpathway of nucleotide excision repair （NER）. Exposure of mice to UVB light or chemicals has elucidated that TC-NER is a critical survival pathway protecting against acute toxic and long-term effects （cancer） of genotoxic exposure. Deficiency in TC-NER is associated with mutations in the CSA and CSB genes giving rise to the rare human disorder Cockayne syndrome （CS）. Recent data suggest that CSA and CSB play differential roles in mammalian TC-NER： CSB as a repair coupling factor to attract NER proteins, chromatin remodellers and the CSA- E3-ubiquitin ligase complex to the stalled RNAPⅡo. CSA is dispensable for attraction of NER proteins, yet in cooperation with CSB is required to recruit XAB2, the nucleosomal binding protein HMGN1 and TFⅡS. The emerging picture of TC-NER is complex： repair of transcription-blocking lesions occurs without displacement of the DNA damage-stalled RNAPⅡo, and requires at least two essential assembly factors （CSA and CSB）, the core NER factors （except for XPC-RAD23B）, and TC-NER specific factors. These and yet unidentified proteins will accomplish not only efficient repair of transcription-blocking lesions, but are also likely to contribute to DNA damage signalling events.

Nucleotide excision repair gene polymorphisms and hepatoblastoma susceptibility in Eastern Chinese children:A five-center case-control study

Objective:Nucleotide excision repair(NER)plays a vital role in maintaining genome stability,and the effect of NER gene polymorphisms on hepatoblastoma susceptibility is still under investigation.This study aimed to evaluate the relationship between NER gene polymorphisms and the risk of hepatoblastoma in Eastern Chinese Han children.Methods:In this five-center case-control study,we enrolled 966 subjects from East China(193 hepatoblastoma patients and 773 healthy controls).The TaqMan method was used to genotype 19 single nucleotide polymorphisms(SNPs)in NER pathway genes,including ERCC1,XPA,XPC,XPD,XPF,and XPG.Then,multivariate logistic regression analysis was performed,and odds ratios(ORs)and 95%confidence intervals(95%CIs)were utilized to assess the strength of associations.Results:Three SNPs were related to hepatoblastoma risk.XPC rs2229090 and XPD rs3810366 significantly contributed to hepatoblastoma risk according to the dominant model(adjusted OR=1.49,95%CI=1.07−2.08,P=0.019;adjusted OR=1.66,95%CI=1.12−2.45,P=0.012,respectively).However,XPD rs238406 conferred a significantly decreased risk of hepatoblastoma under the dominant model(adjusted OR=0.68,95%CI=0.49−0.95;P=0.024).Stratified analysis demonstrated that these significant associations were more prominent in certain subgroups.Moreover,there was evidence of functional implications of these significant SNPs suggested by online expression quantitative trait loci(eQTLs)and splicing quantitative trait loci(sQTLs)analysis.Conclusions:In summary,NER pathway gene polymorphisms(XPC rs2229090,XPD rs3810366,and XPD rs238406)are significantly associated with hepatoblastoma risk,and further research is required to verify these findings.

Eukaryotic nucleotide excision repair： from understanding mechanisms to influencing biology

Repair of bulky DNA adducts by the nucleotide excision repair （NER） pathway is one of the more versatile DNA repair pathways for the removal of DNA lesions. There are two subsets of the NER pathway, global genomic-NER （GG- NER） and transcription-coupled NER （TC-NER）, which differ only in the step involving recognition of the DNA lesion. Following recognition of the damage, the sub-pathways then converge for the incision/excision steps and subsequent gap filling and ligation steps. This review will focus on the GGR sub-pathway of NER, while the TCR sub-pathway will be covered in another article in this issue. The ability of the NER pathway to repair a wide array of adducts stems, in part, from the mechanisms involved in the initial recognition step of the damaged DNA and results in NER impacting an equally wide array of human physiological responses and events. In this review, the impact of NER on carcinogenesis, neurological function, sensitivity to environmental factors and sensitivity to cancer therapeutics will be discussed. The knowledge generated in our understanding of the NER pathway over the past 40 years has resulted from advances in the fields of animal model systems, mammalian genetics and in vitro biochemistry, as well as from reconstitution studies and structural analyses of the proteins and enzymes that participate in this pathway. Each of these avenues of research has contributed significantly to our understanding of how the NER pathway works and how alterations in NER activity, both positive and negative, influence human biology.

Nucleotide excision repair pathway gene polymorphisms are associated with risk and prognosis of colorectal cancer

BACKGROUND Single nucleotide polymorphisms(SNPs)are universally present in nucleotide excision repair(NER)pathway genes,which could make impacts on colorectal carcinogenesis and prognosis.AIM To explore the association of all tagSNPs in NER pathway genes with colorectal cancer(CRC)risk and prognosis in a northern Chinese population by a two-stage case-control design composed of a discovery and validation stage.METHODS Genotyping for NER SNPs was performed using kompetitive allele specific PCR.In the discovery stage,39 tagSNPs in eight genes were genotyped in 368 subjects,including 184 CRC cases and 184 individual-matched controls.In the validation stage,13 SNPs in six genes were analyzed in a total of 1712 subjects,including 854 CRC cases and 858 CRC-free controls.RESULTS Two SNPs(XPA rs10817938 and XPC rs2607775)were associated with an increased CRC risk in overall and stratification analyses.Significant cumulative and interaction effects were also demonstrated in the studied SNPs on CRC risk.Another two SNPs(ERCC2 rs1052555 and ERCC5 rs2228959)were newly found to be associated with a poor overall survival of CRC patients.CONCLUSION Our findings suggest novel SNPs in NER pathway genes that can be predictive for CRC risk and prognosis in a large-scale Chinese population.The present study has referential values for the identification of all-round NER-based genetic biomarkers in predicting the susceptibility and clinical outcome of CRC.

DNA Repair Gene Polymorphisms in the Nucleotide Excision Repair Pathway and Lung Cancer Risk: A Meta-analysis

Objective： A number of studies have reported the association of ＂XPA＂, ＂XPC＂, ＂XPD/ERCC2＂ gene polymorphisms with lung cancer risk. However, the results were conflict. To clarify the impact of polymorphisms of ＂XPA＂, ＂XPC＂, ＂XPD/ERCC2＂, on lung cancer risk, a meta-analysis was performed in this study. Methods： The electronic databases PubMed and Embase were retrieved for studies included in this meta-analysis by ＂XPA＂, ＂XPC＂, ＂XPD/ERCC2＂, ＂lung＂, ＂cancer/neoplasm/tumor/carcinoma＂, ＂polymorphism＂ （An upper date limit of October, 31, 2009）. A meta-analysis was performed to evaluate the relationship among XPA, XPC and XPD polymorphism and lung cancer risks. Results： A total of 31 publications retrieved from Pubmed and Embase included in this study. XPC A939C CC genotype increased lung cancer risk in total population （recessive genetic model： OR=1.23, 95% CI：1.05-1.44; homozygote comparison： OR=1.21,95%CI：1.02-1.43and CC vs. CA contrast： OR=1.25,95%CI：1.06-1.48）, except in Asians. XPD A751C, 751C allele and CC genotype also increased lung cancer risk in total population and in Caucasians （recessive genetic model： Total population： OR=1.20, 95%CI：1.07-1.35）. No significant correlation was found between XPD A751C and lung cancer risk in Asians and African Americans. XPD G312A AA genotype increased lung cancer risk in total population, in Asians and Caucasians（recessive genetic model： Total population： OR=1.20, 95%CI： 1.06-1.36）. No significant association was found between XPA G23A, XPC C499T, XPD C156A and lung cancer risk. Conclusion： Our results suggest that the polymorphisms in XPC and XPD involve in lung cancer risks. XPA polymorphisms is less related to lung cancer risk.

Diffusion of nucleotide excision repair protein XPA along DNA by coarse-grained molecular simulations

Protein XPA plays critical roles in nucleotide excision repair pathway.Recent experimental work showed that the functional dynamics of XPA involves the one-dimensional diffusion along DNA to search the damage site.Here,we investigate the involved dynamical process using extensive coarse-grained molecular simulations at various salt concentrations.The results demonstrated strong salt concentration dependence of the diffusion mechanisms.At low salt concentrations,the one-dimensional diffusion with rotational coupling is the dominant mechanism.At high salt concentrations,the diffusion by three-dimensional mechanism becomes more probable.At wide range of salt concentrations,the residues involved in the DNA binding are similar and the one-dimensional diffusion of XPA along DNA displays sub-diffusive feature.This sub-diffusive feature is tentatively attributed to diverse strengths of XPA-DNA interactions.In addition,we showed that both binding to DNA and increasing salt concentration tend to stretch the conformation of the XPA,which increases the exposure extent of the sites for the binding of other repair proteins.

Global Genome Nucleotide Excision Repair Proteins Rhp7p and Rhp41p Are Involved in Abasic Site Repair of <i>Schizosaccharomyces pombe</i>

The roles of nucleotide excision repair (NER) proteins in removing UV-induced lesions are well defined. There are two distinct NER pathways: global genome NER (GG-NER) and transcription-coupled NER. In human GG-NER, two heteromeric protein complexes, DDB1-DDB2 and XPC-RAD23, are responsible for initial lesion recognition. Here, we examined the genetic interactions between GG-NER and base excision repair (BER) genes during abasic (AP) site repair of Schizosaccharomyces pombe. Mutants of rhp7 (rhp7-rhp16 are functional homologs of DDB1-DDB2) and rhp41 (XPC homolog) were moderately sensitive to methyl methanesulfonate and slightly to sodium bisulfite. Nth1p most actively cleaves the AP site in S. pombe. Deletion of rhp7 or rhp41 from nth1&#916 cells greatly increased their sensitivity to alkylation and deamination, indicating that Rhp7p and Rhp41p are involved in repair of the AP sites generated by the action of DNA glycosylase. Induction of rhp7 and rhp16 genes by different types of DNA damage supports the ability of GG-NER to remove non-bulky lesions. Therefore, GG-NER activity not only targets bulky DNA helix-distorting lesions, but can also efficiently remove AP sites synergistically with BER.

Relationship between ERCC1 (C8092A) single nucleotide polymorphism and efficacy/toxicity of platinum based chemotherapy in advanced non-small cell lung cancer patients

To assses the effect of single nucleotide polymorphism of excision repair cross-complementation group 1 C8092A on the clinical outcome and toxicity in advanced stage non-small cell lung cancer patients receiving first line platinum based chemotherapy.MethodsThis article is a review of the current research on single nucleotide polymorphism and its effect on treatment outcome and toxicity of advanced stage lung cancer.Conclusion The observations indicate that more advanced studies and trials on C8092A SNPs are needed so as to assess if it could be used as a potential biomarker in the future.

ERCC1、K-ras、TP-73在替雷利珠单抗联合TP化疗方案治疗非小细胞肺癌中的评估价值

目的研究探讨核苷酸切除修复交叉互补基因1(ERCC1)、Kirsten-Rous肉瘤病毒蛋白(K-ras)、肿瘤蛋白P73(TP73)在替雷利珠单抗结合紫杉醇+顺铂(TP)化疗方案治疗NSCLC中的评估价值。方法选取2020年1月至2021年12月本院收治的126例NSCLC肺癌患者为研究对象,按随机抽签法分为对照组、观察组,各63例。对照组以TP化疗方案治疗,观察组增加替雷利珠单抗治疗。评估组间临床疗效、肿瘤标记蛋白、免疫指标、生存周期、不良反应。结果观察组患者的客观缓解率为69.84%(44/63)高于对照组患者为52.38%(33/63),观察组疾病控制率为82.54%(52/63),高于对照组患者为66.67%(42/63)(P<0.05)。化疗1周期、化疗3周期、化疗6周期时,观察组ERCC1、K-ras、TP-73水平均低于对照组(P<0.05)。治疗后观察组免疫功能补体C3、补体C4、CD40细胞低于对照组,NK细胞高于对照组(P<0.05)。观察组患者的TTP、PFS、总生存期均高于对照组(P<0.05)。观察组不良反应发生率为19.05%(12/63),对照组为12.70%(8/63),组间比较差异无统计学意义(P>0.05)。结论替雷利珠单抗联合TP化疗方案治疗肺癌有良好的治疗效果,能够改善患者免疫功能,延长患者生存周期,治疗安全性较好,且ERCC1、K-ras、TP-73水平变化可反映替雷利珠单抗联合TP化疗方案在肺癌治疗中的效果,在综合疗效评估中有较高的应用价值。

Inhibition of nucleotide excision repair by arsenic

Inhibition of DNA repair is one proposed mechanism for the co-mutagenicity/co-carcinogenicity of arsenic.This review summarizes the current literature on the effects of arsenic compounds on nucleotide excision repair(NER).Several possible mechanisms for the observed NER inhibition have been proposed.Modulation of the expression of NER proteins has been considered to be one possibility of impairing the NER process.However,data on the effects of arsenic on the expression of NER proteins remain inconsistent.It is more likely that arsenic inhibits the induction of accessory or other key proteins involved in cellular control of DNA repair pathways,such as p53.For example,arsenic affects p53 phosphorylation and p53 DNA binding activity,which could regulate NER through transcriptional activation of downstream NER genes.Although it is important to study possible direct inactivation of NER proteins by arsenic binding,indirect inactivation of proteins having thiol residues critical to their function or zinc finger proteins cannot be negated.For example,nitric oxide(NO) induced in arsenic-treated cells serves as a specific inhibitor of NER,possibly through NO-induced S-nitrosylation of proteins related to DNA repair.Poly(ADP-ribose) polymerase-1,a zinc finger protein implicated in both NER and base excision repair(BER),deserves special attention because of its involvement in NO production and its broad range of protein substrates including many repair enzymes.

上皮性卵巢癌中ERCC1及转录因子Nanog蛋白的表达水平及意义

目的探讨上皮性卵巢癌中核昔酸切除修复交叉互补组1(ERCC1)及转录因子Nanog蛋白的表达水平及意义。方法收集2019年1月至2022年12月在连云港市肿瘤医院妇科行卵巢手术切除的组织标本,其中上皮性卵巢癌组织标本101例(上皮性卵巢癌组),良性卵巢肿瘤组织标本80例(对照组),采用免疫组化检测ERCC1及Nanog蛋白表达水平,并分析与临床病理指标的关系。分别用0mg/L、1mg/L、2mg/L、4mg/L不同浓度的顺铂处理人卵巢癌OVCAR-3细胞24h,以Western blot检测细胞中ERCC1、Nanog蛋白的相对表达量,比较两组间ERCC1及Nanog蛋白的表达水平。结果上皮性卵巢癌组ERCC1、Nanog蛋白的阳性率均明显高于对照组,差异均有统计学意义(χ^(2)值分别为49.960、39.941,P<0.05)。Spearman相关性分析显示,上皮性卵巢癌组中ERCC1与Nanog蛋白表达水平呈正相关(r=0.463,P<0.01);对照组中ERCC1与Nanog蛋白表达水平无相关性(r=0.125,P>0.05)。在上皮性卵巢癌临床病理指标中,FIGO分期为Ⅲ+Ⅳ期的ERCC1、Nanog蛋白的阳性率均明显高于Ⅰ+Ⅱ期(χ^(2)值分别为9.578、9.756),淋巴结转移阳性的ERCC1、Nanog蛋白阳性率均明显高于淋巴结转移阴性(χ^(2)值分别为3.018、2.389),经比较差异均有统计学意义(P<0.05)。1mg/L、2mg/L、4mg/L浓度顺铂处理的ERCC1和Nanog蛋白相对表达量均明显高于0mg/L浓度顺铂处理的相对表达量,经比较差异均有统计学意义(F值分别为8.564、6.571,P<0.05);在ERCC1、Nanog蛋白相对表达量中,顺铂处理浓度1mg/L与0mg/L相比(t值分别为17.236、5.381)、顺铂处理浓度2mg/L与0mg/L相比(t值分别为5.621、6.380)、顺铂处理浓度4mg/L与0mg/L相比(t值分别为12.813、6.810),差异均有统计学意义(P<0.05);且随顺铂浓度的增加,ERCC1、Nanog蛋白相对表达量逐渐升高。结论ERCC1及Nanog蛋白在上皮性卵巢癌中呈现出高表达,可能与该病的发病机理和病情发展具有相关性。顺铂可诱导卵巢癌细胞ERCC1及Nanog蛋白高表达,可能为化疗耐药的潜在机制。

Impact of SNP-SNP interactions of DNA repair gene ERCC5 and metabolic gene GSTP1 on gastric cancer/atrophic gastritis risk in a Chinese population

AIM To investigate the interactions of the DNA repair gene excision repair cross complementing group 5(ERCC5) and the metabolic gene glutathione S-transferase pi 1(GSTP1) and their effects on atrophic gastritis(AG) and gastric cancer(GC) risk.METHODS Seven ERCC5 single nucleotide polymorphisms(SNPs)(rs1047768, rs2094258, rs2228959, rs4150291, rs4150383, rs751402, and rs873601) and GSTP1 SNP rs1695 were detected using the Sequenom MassA RRAY platform in 450 GC patients, 634 AG cases, and 621 healthy control subjects in a Chinese population.RESULTS Two pairwise combinations(ERCC5 rs2094258 and rs873601 with GSTP1 rs1695) influenced AG risk(P_(interaction) = 0.008 and 0.043, respectively), and the ERCC5 rs2094258-GSTP1 rs1695 SNP pair demonstrated an antagonistic effect, while ERCC5 rs873601-GSTP1 rs1695 showed a synergistic effect on AG risk OR = 0.51 and 1.79, respectively). No pairwise combinations were observed in relation to GC risk. There were no cumulative effects among the pairwise interactions(ERCC5 rs2094258 and rs873601 with GSTP1 rs1695) on AG susceptibility(P_(trend) > 0.05). When the modification effect of Helicobacter pylori(H. pylori) infection was evaluated, the cumulative effect of one of the aforementioned pairwise interactions(ERCC5 rs873601-GSTP1 rs1695) was associated with an increased AG risk in the case of negative H. pylori status(P_(trend)= 0.043).CONCLUSION There is a multifarious interaction between the DNA repair gene ERCC5 SNPs(rs2094258 and rs873601) and the metabolic gene GSTP1 rs1695, which may form the basis for various inter-individual susceptibilities to AG.

Cancer Prohibitor-Telomeric DNA Repair Pathways

Telomeres are DNA-protein structures that form protective caps at the end of eukaryotic chromosomes,safeguarding the chromosomes from degradation and maintaining the genomic integrity.When DNA damage occurs,the cell will activate its repair system to fix the errors to prevent cancer.There are three major molecular mechanisms of DNA repair:base excision repair(BER),nucleotide excision repair(NER),and mismatch repair(MMR).In this review article,we discuss the three canonical repair pathways at the telomeres and their functions in cancer prevention and therapy.

核苷酸剪切修复基因mRNA和蛋白对头颈部鳞状细胞癌发生的预测价值研究

目的:探讨核苷酸剪切修复(NER)基因mRNA和蛋白对头颈部鳞状细胞癌(HNSCC)发生的预测价值。方法:选取HNSCC患者98例为病例组,选取18岁及以上健康人群95例为对照组。采用荧光定量PCR实验和反相蛋白微阵列(RPPA)实验检测两组外周血淋巴细胞中9个核心NER基因mRNA和蛋白表达水平。采用Logistic回归分析HNSCC发生的影响因素。绘制受试者工作特征(ROC)曲线分析NER基因mRNA和蛋白表达对HNSCC发生的预测价值。结果:与对照组比较,病例组XPA mRNA和蛋白表达降低,XPB mRNA表达降低(均P<0.05)。XPA mRNA≤19.85和XPA蛋白<0.206是HNSCC发生的独立危险因素(均P<0.05)。单独XPA蛋白、XPA mRNA以及两者联合预测HNSCC发生的曲线下面积(AUC)分别为0.637、0.592、0.674,两者联合的AUC大于单项AUC(均P<0.05)。结论:XPA mRNA和蛋白表达水平是HNSCC发生的影响因素,XPA mRNA和蛋白联合预测HNSCC的发生较两者单独预测的价值更高。

宫颈癌组织ERCC1、hMSH2表达及病理特征与铂类药物抵抗的相关性研究

目的探究宫颈癌组织核苷酸切除修复交叉互补基因1(ERCC1)、错配修复基因2(hMSH2)表达与病理特征及铂类药物抵抗的相关性。方法收集2019年1月—2022年3月我院86例宫颈癌患者病理组织为观察组,另收集同期72例因子宫肌瘤手术切除的正常宫颈组织为对照组。比较2组核苷酸切除修复交叉互补基因1、错配修复基因2表达情况,分析癌组织核苷酸切除修复交叉互补基因1、错配修复基因2表达与病理特征相关性,铂类药物抵抗患者病理特征、核苷酸切除修复交叉互补基因1、错配修复基因2表达情况及铂类药物抵抗的多因素分析,分析核苷酸切除修复交叉互补基因1、错配修复基因2表达对铂类药物抵抗的预测价值。结果观察组核苷酸切除修复交叉互补基因1、错配修复基因2阳性率较对照组高(P<0.05);癌组织核苷酸切除修复交叉互补基因1、错配修复基因2表达与肌层浸润深度、分期、淋巴结转移有关(P<0.05);铂类药物抵抗患者与肌层浸润深度、分期、分化程度、淋巴结转移、核苷酸切除修复交叉互补基因1、错配修复基因2阳性有关(P<0.05);Logistic回归方程分析,结果显示,将肌层浸润深度、分期、分化程度、淋巴结转移控制后,癌组织核苷酸切除修复交叉互补基因1、错配修复基因2阳性仍为宫颈癌患者铂类药物抵抗的危险因素(P<0.05);ROC显示,核苷酸切除修复交叉互补基因1、错配修复基因2阳性联合预测铂类药物抵抗的AUC值最大,为0.702。结论宫颈癌组织核苷酸切除修复交叉互补基因1、错配修复基因2呈高表达状态,且与病理特征及铂类药物抵抗有关,二者可用于预测铂类药物反应性,从而指导临床治疗。

基因TOPOⅡα、TUBB3、ERCC1在小儿肾母细胞瘤组织中的表达及其临床意义

目的探究基因TOPOⅡα、TUBB3、ERCC1在小儿肾母细胞瘤组织中的表达及其临床意义。方法选择40例肾母细胞瘤患儿的病理组织标本,另同期采集距离肿瘤组织2~3 cm的癌旁组织标本作为对照组。分析两者拓扑异构酶Ⅱα(TOPOⅡα)、3型β微管蛋白编码基因(TUBB3)、核苷酸切除修复交叉互补基因(ERCC1)表达情况;另分析TOPOⅡα、TUBB3、ERCC1与肾母细胞瘤患儿病理特征的相关性。结果癌组织中TOPOⅡα、TUBB3、ERCC1高表达率均高于癌旁组织,差异有统计学意义(P<0.05)。TOPOⅡα高表达者病理分期Ⅲ~Ⅳ占比率高于中低表达者,差异有统计学意义(P<0.05);ERCC1高表达者病理分期Ⅲ~Ⅳ占比率高于中低表达者,差异有统计学意义(P<0.05)。结论TOPOⅡα、TUBB3、ERCC1在小儿肾母细胞瘤中的表达水平均高于癌旁组织,其中TOPOⅡα、ERCC1均与疾病病理分期有关,二者在肾母细胞瘤的发生及发展中具有重要作用。

核苷酸切除修复基因表达低下与肺癌的关系

目的 探讨核苷酸切除修复基因ERCCl(excisionrepaircross -complementing 1 )的表达与肺癌发病的关系。方法 用RT -PCR(reversetranscription -polymerasechainreaction)技术检测 1 50例肺癌组织和 50例正常肺组织中ERCCl基因的mRNA表达 ;免疫组化法检测ERCC1和癌变相关基因P53、C -MYC、K -RAS、BCL - 2和hTERT(端粒酶逆转录酶 )基因的蛋白表达 ;分析有关暴露因素对修复基因ERCCl表达的影响 ,并探讨ERCC1基因与P53、C -MYC、K -RAS、BCL - 2和hTERT等癌变相关基因的关系。结果 30 7% (46/ 1 50 )的肺癌组织和 4 0 % (2 / 50 )的正常肺组织存在ER CC1基因的表达低下 ;修复基因ERCC1表达低下与肺癌发生有关联 ,其危险度OR为 1 0 62 (2 38,65 98) ,P <0 0 0 1 ,人群归因危险度PARP为 8 87%。分析各种可能影响ERCC1基因表达的暴露因素 ,发现吸烟可抑制ERCC1基因的表达。另外发现 ,P53突变蛋白和K -RAS癌基因的过度表达与ERCC1表达低下有关。P分别为 0 0 388和 0 0 4 5 6。ERCC1与C -MYC、BCL - 2和hTERT基因的表达无关联。结论 ERCC1表达低下在肺癌发病中起着重要的作用 。

DNA损伤修复机制——解读2015年诺贝尔化学奖

Tomas Lindahl,Paul Modrich和Aziz Sancar三位科学家因发现"DNA损伤修复机制"获得了2015年诺贝尔化学奖.Lindahl首次发现Escherichia Coli中参与碱基切除修复的第一个蛋白质——尿嘧啶-DNA糖基化酶(UNG);Modrich重建了错配修复的体外系统,从大肠杆菌到哺乳动物深入探究了错配修复的机制;Sancar利用纯化的Uvr A、Uvr B、Uvr C重建了核苷酸切除修复的关键步骤,阐述了核苷酸切除修复的分子机制.DNA损伤是由生物所处体外环境和体内因素共同导致的,面对不同种类的损伤,机体启动多种不同的修复机制修复损伤,保护基因组稳定性.这些修复机制包括:光修复(light repairing);核苷酸切除修复(nucleotide excision repair,NER);碱基切除修复(base excision repair,BER);错配修复(mismatch repair,MMR);以及DNA双链断裂修复(DNA double strand breaks repair,DSBR).其中DNA双链断裂修复又分同源重组(homologous recombination,HR)和非同源末端连接(non-homologous end joining,NHEJ)两种方式.本文将对上述几种修复的机制进行总结与讨论.

核苷酸切除修复基因XPD反义RNA表达载体的构建及功能研究

目的 构建核苷酸切除修复基因XPD反义RNA表达载体 ,初步探讨其对肺癌细胞DNA损伤修复能力及药物敏感性的影响。方法 通过RT PCR技术获取XPDcDNA (2～ 6 6 7bp)片段并反向插入真核 7表达载体反义载体pcDNA3 1,采用脂质体法将构建的载体质粒转染肺癌细胞株A5 4 9,经G4 18筛选 ,采用抗肿瘤药物阿霉素、顺铂对细胞进行染毒干预 ,干预结果采用SCGE和MTT综合判定。结果 转染细胞XPDmRNA表达受到抑制。单细胞凝胶电泳显示转染细胞DNA损伤修复能力降低。MTT法显示转染细胞药物敏感性增高。结论 XPD反义RNA能降低肺癌细胞DNA损伤修复能力 。

核苷酸切除修复基因表达水平与肺癌易感性的关系

[目的 ]探讨核苷酸切除修复基因表达水平与肺癌易感性关系。 [方法 ]采用病例 对照分子流行病学方法 ,以RT PCR技术检测 98例原发性肺癌患者和 112名健康者外周血淋巴细胞核苷酸切除修复基因 (XPB、XPC、XPG、ERCC1)表达水平 ,比较基因表达水平与肺癌易感性的关系。 [结果 ]肺癌病例组 4种基因的表达水平均低于健康对照组 ,其中XPB和XPC表达水平在两组之间有显著性差异 ,吸烟人群中病例与对照组基因表达水平差异大于非吸烟人群与对照组的差异 ,低表达XPB和XPC的人群患肺癌的相对危险度分别是高表达人群的 2 .0 6和 2 .2 7倍。 [结论 ]低表达XPB和XPC的人群肺癌发病风险增高。