Construction of recombinant herpes simplex virus 2 expressing enhanced green fluorescent protein using CRISPR/Cas9 / 中华微生物学和免疫学杂志

Objective:To construct a recombinant herpes simplex virus 2 (HSV-2) expressing enhanced green fluorescent protein (EGFP) using clustered, regularly interspaced, short palindromic repeat/CRISPR-associated nuclease 9 (CRISPR/Cas9) technology.Methods:Four strategies for inserting exogenous EGFP gene into HSV-2 genome using CRISPR/Cas9 technology were designed: (1) conventional homology-directed repair: circular two homology arm donor-mediated gene knock-in; (2) linearized single homology arm donor-mediated gene knock-in; (3) homology-independent targeted integration; (4) conventional homology-directed repair-mediated by cell lines stably expressing Cas9 and sgRNA.Results:The recombinant virus HSV-2-EGFP was successfully constructed based on the second, the third and the fourth strategies. The second strategy was the most efficient, followed by the third and the fourth strategies. The purified recombinant virus could stably express green fluorescent protein in seven passages and shared similar growth characteristics in Vero cells to the parental virus.Conclusions:Linearized single homology arm donor could increase the efficiency of gene knock-in, and cell lines stably expressing Cas9 and sgRNA could increase the efficiency of gene knock-in mediated by homology-directed repair.

ZNF451 promotes DNA damage repair by recruiting 53BP1/MDC1 in A549 and HeLa cells / 中华放射医学与防护杂志

Objective:To investigate the role of SUMO E3 ligase ZNF451 in DNA damage repair and explore the underlying mechanism in non-small cell lung cancer A549 cells and cervical cancer HeLa cells.Methods:A549 cells and HeLa cells were irradiated with γ-ray irradiation or treated with etoposide. Cell proliferation viability was detected by the cell counting kit-8 assay. Protein expression was detected by Western blot assay. DNA damage repair level was detected by DR-GFP plasmid system, and the spatial positioning was detected by immunofluorescence.Results:Etoposide decreased the expression level of ZNF451 in a dose- and time- dependent manner. After treatment with 30, 50, 80 μmol/L etoposide, the cell viability were reduced after the knockdown of ZNF451 in A549 and HeLa cells(A549: t = 27.62, 25.61, 5.32, P<0.01; HeLa: t = 30.77, 21.28, 4.18, P<0.01). Furthermore, ZNF451 was recruited at DNA damage sites. A co-localization and endogenous interaction were found between ZNF451 and γ-H2AX after the treatment of irradiation or etoposide. Moreover, the expression level of γ-H2AX was significantly increased after treatment with 30, 50, 80 μmol/L etoposide(A549: t = 6.12, 10.67, 4.68, P<0.01; HeLa: t = 7.94, 9.81, 15.12, P<0.01)and the repair efficiency of NHEJ was reduced in ZNF451 knockdown cells( t = 18.60, P<0.05). Finally, the immunofluorescence assay showed that ZNF451 was co-localizated with 53BP1 and MDC1 after irradiation or etoposide treatment. Conclusions:Knockdown of ZNF451 inhibits cell proliferation and increases the level of DNA damage in A549 and HeLa cells. ZNF451 was recruited to DNA damage sites after DSBs and participated in NHEJ repair by co-localizing with DNA damage repair factor 53BP1/MDC1.

cGAS guards against chromosome end-to-end fusions during mitosis and facilitates replicative senescence

As a sensor of cytosolic DNA, the role of cyclic GMP-AMP synthase (cGAS) in innate immune response is well established, yet how its functions in different biological conditions remain to be elucidated. Here, we identify cGAS as an essential regulator in inhibiting mitotic DNA double-strand break (DSB) repair and protecting short telomeres from end-to-end fusion independent of the canonical cGAS-STING pathway. cGAS associates with telomeric/subtelomeric DNA during mitosis when TRF1/TRF2/POT1 are deficient on telomeres. Depletion of cGAS leads to mitotic chromosome end-to-end fusions predominantly occurring between short telomeres. Mechanistically, cGAS interacts with CDK1 and positions them to chromosome ends. Thus, CDK1 inhibits mitotic non-homologous end joining (NHEJ) by blocking the recruitment of RNF8. cGAS-deficient human primary cells are defective in entering replicative senescence and display chromosome end-to-end fusions, genome instability and prolonged growth arrest. Altogether, cGAS safeguards genome stability by controlling mitotic DSB repair to inhibit mitotic chromosome end-to-end fusions, thus facilitating replicative senescence.

Identification of Medicinal Aconitum Species Based on ITS2 Sequences and Analysis of Genetic Relationship / 中国实验方剂学杂志

ObjectiveThe internal transcribed spacer （ITS） 2 region of ribosomal gene， a DNA barcode， was employed to identify 12 medicinal Aconitum species and the genetic relationship among the species was analyzed. MethodA total of 30 samples of the 12 species were collected. The DNA was extracted with spin column plant genomic DNA kit and the universal primers of ITS2 sequence were used for polymerase chain reaction （PCR） amplification， followed by electrophoresis detection and bi-directional sequencing. The yielded sequences were aligned and spliced by CodonCode Aligner 17.0 and sequence variation was analyzed by MEGA 7.0. The secondary structure was predicted by ITS2 Database and the neighbor-joining （NJ） method was applied to generate the phylogenetic tree. ResultThe ITS2 sequences of the 12 species were 220-221 bp， with the average guanine and cytosine （GC） content of 64.09%， 140 variable sites， 137 informative sites， and 81 conservative sites. The intraspecific genetic distance （K2P） was smaller than the interspecific genetic distance. According to the secondary structures of ITS2 sequences and NJ cluster analysis， A. scaposum， A. sinomontanum， and A. barbatum had close genetic relationship， while the rest nine showed close kinship， particularly A. soongaricum and A. yinschanicum. ConclusionITS2 sequence is of great value for the molecular identification and genetic relationship determination of Aconitum， which provides a new method for the study of ethnomedicine.

An efficient marker-free genome editing method for Aspergillus niger / 生物工程学报

Aspergillus niger is an important industrial strain which has been widely used for production of enzymes and organic acids. Genome modification of A. niger is required to further improve its potential for industrial production. CRISPR/Cas9 is a widely used genome editing technique for A. niger, but its application in industrial strains modification is hampered by the need for integration of a selection marker into the genome or low gene editing efficiency. Here we report a highly efficient marker-free genome editing method for A. niger based on CRISPR/Cas9 technique. Firstly, we constructed a co-expression plasmid of sgRNA and Cas9 with a replication initiation region fragment AMA1 (autonomously maintained in Aspergillus) by using 5S rRNA promoter which improved sgRNA expression. Meanwhile, a strain deficient in non-homologous end-joining (NHEJ) was developed by knocking out the kusA gene. Finally, we took advantage of the instability of plasmid containing AMA1 fragment to cure the co-expression plasmid containing sgRNA and Cas9 through passaging on non-selective plate. With this method, the efficiency of gene editing reached 100% when using maker-free donor DNA with a short homologous arm of 20 bp. This method may facilitate investigation of gene functions and construction of cell factories for A. niger.

Identification of Chinese medicine sea snake based on cytochrome B (Cytb) / 中国中药杂志

The identification of species primordium has been one of the hot issues in the identification of traditional Chinese medicine. Sea snake is one of the most valuable Chinese medicinal materials in China. In order to understand the origin and varieties of sea snake in the market, we studied the molecular identification of 46 sea snakes by cytochrome B(Cytb). After comparison and manual correction, the sequence length was 582 bp, and the content of A+T(58.9%) was higher than that of G+C(41.1%). There exist 197 variable sites and 179 parsimony-informative sites of the sequence. There are 44 kinds of sequence alignment with consistency equal to 100%, and 2 kinds equal to 96%. A total of 408 Cytb effective sequences were downloaded from GenBank database, with a total of 68 species. Phylogenetic tree of a total of 454 sea snake sequences with the samples in this study were constructed by neighbor-joining trees and Bayesian inference method, respectively, which can identify 42 samples of medicinal materials, while 4 samples can not be identified because of their low node support. The results showed that the species of the sea snake medicine were at least from 2 genera and 5 species, namely, Aipysurus eydouxii, Hydrophis curtus, H. caerulescen, H. curtus, H. ornatus and H. spiralis. This study suggested that the original species of commercial sea snake are very complex and can provide insight into the identification of sea snakes.

Research progress on HPV-positive oropharyngeal carcinoma sensitive to radiation therapy / 口腔疾病防治

@#Oropharyngeal carcinoma is a highly heterogeneous disease that is mainly caused by tobacco and alcohol abuse or high-risk human papillomavirus (HPV) infection. HPV-positive oropharyngeal carcinoma and HPV-negative oropharyngeal carcinoma have obvious differences in etiology, epidemiology and prognosis; therefore, different methods should be adopted for treatment. It is known that the TP53 gene is not mutated in HPV-positive oropharyngeal carcinoma, and radiation therapy can activate it and induce cell apoptosis via DNA damage. There are common repair pathways to DNA damage, such as nonhomologous end joining, and this pathway is more sensitive to radiotherapy under the inhibition of HPV oncoprotein. In addition, the further activation of the immune response under the effect of radiation also participates in the elimination of tumors. In this paper, we reviewed the research on the sensitivity of HPV-positive oropharyngeal cancer to radiotherapy to provide a scientific basis for targeted treatment for various pathogenic factors and clinical stages of oropharyngeal cancer in the future.

Role of deubiquitinating enzymes in DNA double-strand break repair / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

DNA is the hereditary material in humans and almost all other organisms. It is essential for maintaining accurate transmission of genetic information. In the life cycle, DNA replication, cell division, or genome damage, including that caused by endogenous and exogenous agents, may cause DNA aberrations. Of all forms of DNA damage, DNA double-strand breaks (DSBs) are the most serious. If the repair function is defective, DNA damage may cause gene mutation, genome instability, and cell chromosome loss, which in turn can even lead to tumorigenesis. DNA damage can be repaired through multiple mechanisms. Homologous recombination (HR) and non-homologous end joining (NHEJ) are the two main repair mechanisms for DNA DSBs. Increasing amounts of evidence reveal that protein modifications play an essential role in DNA damage repair. Protein deubiquitination is a vital post-translational modification which removes ubiquitin molecules or polyubiquitinated chains from substrates in order to reverse the ubiquitination reaction. This review discusses the role of deubiquitinating enzymes (DUBs) in repairing DNA DSBs. Exploring the molecular mechanisms of DUB regulation in DSB repair will provide new insights to combat human diseases and develop novel therapeutic approaches.

Regulation of DNA double-strand break repair pathway choice: a new focus on 53BP1 / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Maintenance of cellular homeostasis and genome integrity is a critical responsibility of DNA double-strand break (DSB) signaling. P53-binding protein 1 (53BP1) plays a critical role in coordinating the DSB repair pathway choice and promotes the non-homologous end-joining (NHEJ)-mediated DSB repair pathway that rejoins DSB ends. New insights have been gained into a basic molecular mechanism that is involved in 53BP1 recruitment to the DNA lesion and how 53BP1 then recruits the DNA break-responsive effectors that promote NHEJ-mediated DSB repair while inhibiting homologous recombination (HR) signaling. This review focuses on the up- and downstream pathways of 53BP1 and how 53BP1 promotes NHEJ-mediated DSB repair, which in turn promotes the sensitivity of poly(ADP-ribose) polymerase inhibitor (PARPi) in BRCA1-deficient cancers and consequently provides an avenue for improving cancer therapy strategies.

MRN complex is an essential effector of DNA damage repair / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Genome stability can be threatened by both endogenous and exogenous agents. Organisms have evolved numerous mechanisms to repair DNA damage, including homologous recombination (HR) and non-homologous end joining (NHEJ). Among the factors associated with DNA repair, the MRE11-RAD50-NBS1 (MRN) complex (MRE11-RAD50-XRS2 in

Effect and mechanism of down-regulating REV7 expression on the radiosensitivity of human colon cancer cell HCT116 / 中华放射肿瘤学杂志

Objective@#To evaluate the effect and mechanism of down-regulating the expression of REV7 on the radiosensitivity of human colon cancer cell HCT116.@*Methods@#HCT116 cells were cultured and the expression of REV7 was down-regulated by RNA interference technique. HCT116 cells were divided into the blank group, negative control transfected with negative RNA oligo group and REV7 expression down-regulation transfected with REV7 RNA oligo group, respectively. The cell proliferation was determined by colony formation assay. The expression levels of the proteins of relevant genes were detected by Western blot. The level of cell apoptosis and non-homologous end joining was evaluated.@*Results@#The colony formation rate was significantly reduced in THE REV7 siRNA group after 6Gy irradiation (P<0.05). The down-regulating efficiency rate of REV7 gene was>60% in the REV7 siRNA group. The expression levels of γH2AX and Caspase9 were significantly up-regulated, whereas those of KU80 and XRCC4 were remarkably down-regulated in the REV7 siRNA group (all P<0.05).@*Conclusions@#The radiosensitivity of human colon cancer cell HCT116 can be increased by down-regulating the expression of REV7. The underlying mechanism may be related to the lower incidence rate of non-homologous end joining.

Effect and mechanism of down-regulating REV7 expression on the radiosensitivity of human colon cancer cell HCT116 / 中华放射肿瘤学杂志

Objective To evaluate the effect and mechanism of down-regulating the expression of REV7 on the radiosensitivity of human colon cancer cell HCT116.Methods HCT116 cells were cultured and the expression of REV7 was down-regulated by RNA interference technique.HCT116 cells were divided into the blank group,negative control transfected with negative RNA oligo group and REV7 expression down-regulation transfected with REV7 RNA oligo group,respectively.The cell proliferation was determined by colony formation assay.The expression levels of the proteins of relevant genes were detected by Western blot.The level of cell apoptosis and non-homologous end joining was evaluated.Results The colony formation rate was significantly reduced in THE REV7 siRNA group after 6Gy irradiation (P＜0.05).The down-regulating efficiency rate of REV7 gene was ＞ 60％ in the REV7 siRNA group.The expression levels of γ H2AX and Caspase9 were significantly up-regulated,whereas those of KU80 and XRCC4 were remarkably down-regulated in the REV7 siRNA group (all P＜0.05).Conclusions The radiosensitivity of human colon cancer cell HCT116 can be increased by down-regulating the expression of REV7.The underlying mechanism may be related to the lower incidence rate of non-homologous end joining.

Haplotype diversity in medically important red scorpion (Scorpiones: Buthidae: Hottentotta tamulus) from India

The medically important Indian red scorpion, Hottentotta tamulus, is one of the most poisonous scorpions of Indian subcontinent. We studied the haplotype diversity in eight populations of H. tamulus based on mitochondrial cytochrome oxidase subunit I (COI) partial gene sequence. Analyses revealed 22 haplotypes with a haplotype diversity of 0.941 and nucleotide diversity of 0.023. For the first two codon positions both transition and transversion types of substitutions were equally likely and the test for neutrality was not rejected. However, codon substitution pattern indicated that the gene has experienced purifying selection. Model-based clustering method indicated that the eight populations form three groups that correspond to high, moderate and low rainfall areas, indicating that there is biogeographical separation of haplotypes. Populations from three groups formed distinct clades in maximum likelihood analysis and median joining genetic network and were statistically supported by low within group and high among group variation in analyses of molecular variance. We provide the first account of haplotype diversity in Indian red scorpions and their biogeographical separation.

Inactivation of the NHEJ Activity of DNA-PKcs Prevents Fanconi Anemia Pre-Leukemic HSC Expansion

Fanconi anemia (FA) is a genetic disorder characterized by bone marrow failure and high risk of cancer particularly leukemia. Here we show that inactivation of the non-homologous end-joining (NHEJ) activity of DNA-PKcs prevented DNA damage-induced expansion of FA pre-leukemic hematopoietic stem cells (HSCs). Furthermore, we performed serial BM transplantation to demonstrate that the DNA damage-induced expanded FA HSC compartment contained pre-leukemic stem cells that required the NHEJ activity of DNA-PKcs to induce leukemia in the secondary recipients. These results suggest that NHEJ may collaborate with FA deficiency to promote DNA damage-induced expansion of pre-leukemic HSCs.

Genetic polymorphisms and genetic relationship of 24 autosomal STR loci in Gelao and Miao population of Guizhou / 解放军医学杂志

Objective: To investigate the genetic polymorphisms of 24 autosomal short tandem repeats (STR) loci in Gelao and Miao populations dwelled in Guizhou province, and explore the population genetic relationships and evaluate their application value on forensic medicine. Methods: The DNA samples of 732 unrelated individuals (399 Guizhou Gelao population and 333 Guizhou Miao population) were amplified using SureID® PanGlobal kit, and the PCR products were analyzed by electrophoresis through 3500XL genetic analyzer. The fragment sizes of alleles were subsequently analyzed by GeneMapper ID-X v1.5. Allele frequencies and forensic genetic parameters of 24 STR loci were statistically analyzed and compared with the available data of other populations from different races and regions. Results: For Guizhou Gelao and Miao populations, the individual discrimination power (DP) ranged from 0.7833 to 0.9909 and 0.8010 to 0.9909, respectively; the polymorphic information content (PIC) ranged from 0.5608 to 0.9385 and 0.5677 to 0.9414, respectively; the total discrimination power (TDP) were 1-7.6036 × 10-30 and 1-6.8630 × 10-30, respectively, and the cumulative probability of exclusion (CPE) were 1-1.9608 × 10-11 and 1-1.9738 × 10-14, respectively. Analysis with the matrix of Nei's DA genetic distance indicated that the genetic distance was the smallest (0.0205) between Guizhou Gelao and Hubei Han populations, while was the largest (0.0449) between Guizhou Gelao and Yunnan Miao populations; the genetic distance was minimum (0.0033) between Guizhou Miao and Hunan Han populations, while was maximal (0.0363) between Guizhou Miao and Yunnan Miao. Conclusions: The 24 STR loci are abundant in genetic polymorphism in Guizhou Gelao and Miao populations. It is of great significance to study the genetic diversity of different ethnic groups in order to understand their origin, migration and interrelationship.

Research progress of SUMOylation modification in DNA double-strand break repair / 国际生物医学工程杂志

The small ubiquitin-like modified protein (SUMO) is a protein structurally similar to ubiquitin which is involved in post-translational modification of proteins. SUMOylation refers to the process that SUMO molecule covalently binding to the specific lysine site of target proteins through maturation, activation, binding and ligation by ubiquitin-like specific protease 1 (Ulp1), E1 activating enzyme, E2 binding enzyme, and E3 ligase. SUMOylation alters the activity of target proteins, which is involved in the regulation of various cellular functions such as transcriptional regulation, regulation of embryonic development, cellular stress, maintenance of chromatin structure and genomic stability. In recent years, it has been found that SUMOylation modification is also widely involved in DNA damage repair, especially DNA double-strand breaks (DSBs), which are the most serious types of DNA damage. SUMOylation is involved in almost all processes of DSBs repair, so its role in DNA damage repair has become a research hotspot. In this paper, the research progress of the regulation of SUMOylation in DSBs repair was reviewed.

Identificación in silico de moléculas potencialmente inhibidoras de CDK5, proteína relacionada con la enfermedad de Alzheimer / Identification in silico of potentially inhibitive molecules of CDK5, protein related with the Alzheimer´s disease

Introducción: La enfermedad de Alzheimer exhibe un compromiso neurodegenerativo e irreversible. Hoy, numerosas investigaciones promueven la inhibición de algunas quinasas para su tratamiento, de especial mención la CDK5. Objetivo: Identificación de nuevas moléculas con posibilidad de interactuar con la proteína quinasa dependiente de ciclina 5, CDK5, inhibiendo su función. Material y Métodos: Se realizó un estudio in silico, para lo cual se extrajeron 911 moléculas de pubchem, y mediante AutoDock Vina se hicieron acoplamientos moleculares con la proteína CDK5 extraída de Protein Data Bank y con un inhibidor conocido para la proteína. Además se realizó un acoplamiento inverso para la identificación de otros posibles blancos moleculares con los mejores ligandos seleccionados. Resultados: Con los resultados obtenidos fueron identificadas cinco moléculas con valores de afinidad entre -11,6 hasta -17,7 Kcal/mol que se unen en el sitio activo de la proteína, de igual forma que lo hace el inhibidor conocido de la misma, e interactúan con los residuos cisteína 83 y glutamina 81. Conclusiones: Las moléculas identificadas pueden interactuar con la CDK5 a nivel de su sitio activo, por lo que podrían actuar como inhibidores de esta quinasa. Esto abre una futura ventana terapéutica en el tratamiento de la enfermedad de Alzheimer)AU)

Introduction: The illness of Alzheimer exhibits a neurodegenerative and irreversible commitment. Today, numerous investigations promote the inhibition of some kinases to the treatment, of special mention the CDK5. Objective: Identification of new molecules witch are able to interact with the cicline dependent kinase protein 5, CDK5, inhibiting their function. Material and Methods: it was carried out a study in silico, for that 911 pubchem molecules were extracted, and by means of AutoDock Vina molecular joining were made with the protein CDK5 extracted from the Protein Data Bank and with a well-known inhibitor for the protein. It was also carried out an inverse joining for the identification of other possible molecular targets with the best selected ligands. Results: With the obtained results five molecules were identified with values of likeness among -11,6 until -17,7 Kcal/mol that joins in the active site of the protein, in the same form that makes it the well-known inhibitor of the CDK5, and interact with the residuals cysteine 83 and glutamine 81. Conclusions: The identified molecules can interact with the CDK5 at level of their active place, for what you/they could act as inhibitors of this quinasa. This opens a future therapeutic window in the treatment of the illness of Alzheimer(AU)

"Survey and analyses on the satisfaction degree of the postgraduate in professional degree in ""The Joining Together of Double-Track""education model" / 中华医学教育探索杂志

Objective To survey the satisfaction degree of the postgraduates in professional degree with The Joining Together of Double-Track education model in the current stage of professional degree graduate education and standardized training of residents in China. Methods According to various factors, such as the current situation of postgraduates in medical universities, we sought the opinions of relevant experts to design questionnaire. Meanwhile, to enhance the reliability of the questionnaire and the survey, we chose the postgraduates of Shengjing Hospital of China Medical University first to do the pre-survey, and according to the feedback, we adjusted part of the aspects, thus formed a formal questionnaire, which included the satisfaction with training of clinical practice ability, training of research ability, and tutors' assessment etc. Finally, the Chinese New Youth Forum online released the questionnaires, selecting the postgraduates in professional degree who were participating in, or had participated in the completion of the standardized training as the participants, which took place between March 2016 and May 2016. SPSS 16.0 was used for statistical analysis. The evaluation results of different majors were tested by Kruskal-Wallis rank sum test. Results According to the results of the survey, the aspects in the clinical resident standard-ized training that the 1000 postgraduates were more satisfied with were as follows: training time [42.8%(n=428)], training center [41.8% (n=418)], training of clinical practice ability [41.6% (n=416)], tutors [40.2%(n=402)], economic income [38.8%(n=388)], department arrangements [38.4% (n=384)], training of research ability [37.5%(n=375)]. There is a significant difference in the satisfaction degree of different pro-fessional graduate students in theJoining Together of Double-Trackeducation model (P<0.05). ConclusionThe Joining Together of Double-Track education model should be compatible with the training objectives of postgraduates in professional degree. Much more attention should be paid to the post-graduates, satisfac-tion degree with the clinical resident standardized training, as well as the requirements during the training period, improve the evaluation of graduate students' ability of scientific research, econo-mic income and so on, so as to improve the training system for the postgraduates.

Tyrosyl-DNA phosphodiesterases: potential targets for cancer treatment / 药学学报

DNA topoisomerases-mediated DNA damages are generated from exogenous and endogenous effects, which need to be metabolized or repaired to maintain genome stability involving in many of repair enzymes. Tyrosyl-DNA phosphodiesterase 1 (TDP1) and tyrosyl-DNA phosphodiesterase 2 (TDP2) are two DNA repair enzymes discovered recently. TDP1 and TDP2 have the ability to hydrolyze the tyrosyl-phosphodiester bond of the phenol of tyrosine with 3'-and 5'-DNA end, respectively, which are contained in the metabolites of the damaged DNA mediated by topoisomerase 1 and topoisomerase 2, respectively. The abnormal activation and expression of TDP1 or TDP2 is the important reason for cancer development. Therefore, TDP1 and TDP2 have been regarded as potential targets in cancer therapy. In this review, we discuss the rationales of their potential as targets and development of their inhibitors together with topoisomerase poisons or DNA damaging agents.

Effect and mechanism of neuroepithelial cell transforming gene 1 on cellular radiosensitivity / 中华放射医学与防护杂志

Objective To study the effect of neuroepithelial cell transforming gene 1 (Net1) on the cellular radiosensitivity and underlying mechanism.Methods Real-time quantitative PCR was used to measure the variations in Net1 expression level upon irradiation.Radiosensitivity was analyzed by colonyforming assay after Net1-siRNAs.Net1-associated proteins were identified by co-immunoprecipitation.Results The Net1 mRNA level in the cells was increased significantly (t =-10.52,P ＜ 0.05) after irradiation.Compared to the control group,siRNA-mediated silencing of Net1 enhanced cell radiosensitivity (t =15.31,11.65,P ＜0.05).Net1 was found to interact with Ku70,Ku80 and DNA-PKcs under either normal conditions or after irradiation.Conclusions Net1 could protect cells from irradiation by interaction with DNA repair proteins in non-homologous end joining pathway.