Construction and biological characterization of a Proteus mirabilis strain with modABC gene deletion / 南方医科大学学报

OBJECTIVE@#To construct a modABC gene knockout strain of Proteus mirabilis and explore the effect of modABC gene deletion on biological characteristics of Proteus mirabilis.@*METHODS@#Fusion PCR was used to obtain the fusion gene of modABC and the kanamycin-resistant gene Kn, which was ligated with the suicide vector pCVD442 and transduced into Proteus mirabilis. The modABC gene knockout strain of Proteus mirabilis was obtained after homologous recombination with the suicide vector. PCR and Sanger sequencing were used to identify genomic deletion of modABC gene in the genetically modified strain. The concentration of molybdate in the wild-type and gene knockout strains was determined using inductively coupled plasma mass spectrometry (ICP-MS), and their survival ability in LB medium was compared under both aerobic and anaerobic conditions.@*RESULTS@#PCR and sanger sequencing confirmed genomic deletion of modABC gene in the obtained Proteus mirabilis strain. The concentration of intracellular molybdenum in the modABC gene knockout strain was 1.22 mg/kg, significantly lower than that in the wild-type strain (1.46 mg/kg, P < 0.001). Under the aerobic condition, the modABC gene knockout strain grown in LB medium showed no significant changes in survival ability compared with the wild-type strain, but its proliferation rate decreased significantly under the anaerobic condition and also when cultured in nitrate-containing LB medium under anaerobic condition.@*CONCLUSION@#Homologous recombination with the suicide vector can be used for modABC gene knockout in Proteus mirabilis. modABC gene participates in molybdate uptake and is associated with anaerobic growth of Proteus mirabilis in the presence of nitrate.

The efficacy and safety comparison of radium-223 in the treatment of mCRPC patients with and without homologous recombination repair gene mutation / 中华泌尿外科杂志

Objective:To compare the efficacy and safety of radium-223 in the treatment of metastatic castration-resistant prostate cancer (mCRPC) patients with and without homologous recombination repair (HRR) gene mutation.Methods:The clinical data of 27 patients with mCRPC bone metastases who received radium-223 therapy from April 2021 to November 2022 in Renji Hospital Affiliated to Shanghai Jiaotong University School of Medicine were retrospectively analyzed. Among the 27 mCRPC patients, 18 patients carrying HRR gene mutations belonged to the HRD(+ ) group, and 9 patients without HRR gene mutation belonged to the HRD(-) group. The age of patients in HRD(+ ) group was 69.5 (63.8, 77.0) years old, alkaline phosphatase (ALP) was 243.0 (82.8, 301.3) U/L, prostate specific antigen (PSA) was 71.6 (7.3, 329.8) ng/ml, pain score was 3.0 (1.0, 5.0) points. Eastern Cooperative Oncology Group (ECOG) score ranged from 0 to 1 points in 7 cases, and 2 points in 11 cases. In the HRD(-) group, the median age was 72.0 (64.5, 76.5) years old, ALP was 88.0 (67.5, 260.6) U/L, PSA was 19.1 (1.1, 117.8) ng/ml, and pain score was 2.0 (0, 4.5) points. The ECOG score ranged from 0 to 1 in 4 cases, and 2 in 5 cases in the HRD(-) group. There was no significant difference in the above general data between the two groups ( P>0.05). All patients received radium-223 treatment every 4 weeks, no more than 6 times. The changes of ALP, PSA, pain score and hematological adverse reactions were compared between the two groups. Results:In the HRD(+ ) group, the median number of radium-223 treatment was 4.5 (3.0, 5.3) couses, 4 patients (22.2%) completed 6 courses, and 6 patients died of prostate cancer during follow-up. In the HRD(-) group, the median number of radium treatment was 4.0 (2.5, 6.0) couses, 3 patients (33.3%) completed 6 courses, and 1 patient died of prostate cancer during follow-up. There was no significant difference in the number of radium treatment courses between the two groups ( P=0.320). ALP in HRD(+ ) group was 101.8 (61.3, 147.0) U/L after radium-223 treatment, which was significantly lower than that before treatment ( P=0.002). ALP in HRD(-) group was 73.0 (64.0, 113.5) U/L after radium-223 treatment, and it was not significantly different from that before treatment ( P=0.327). The rate of ALP response (ALP decrease >10%) in HRD(+ ) group was significantly higher than that in HRD(-) group [83.3% (15/18) vs. 44.4% (4/9), P=0.037]. PSA was 105.9(5.2, 798.4) ng/ml in HRD (+ ) group after radium-223 treatment, and was 25.6(0.8, 1 031.0) ng/ml in HRD(-) group, and they were not significantly different from that before treatment ( P=0.145, P=0.386). There were no significant differences in the rate of PSA response (PSA decrease>10%) between HRD(+ ) group and HRD(-) group [38.9% (7/18) vs. 22.2% (2/9), P=0.386]. The median pain score of HRD(+ ) group was 3.0 (0, 4.0) points after treatment, which was significantly lower than that before treatment ( P=0.028). The pain score of HRD(-) group was 1.0(0, 3.0) points after treatment, and it was not significantly different from that before treatment ( P=0.129). There was no significant difference in pain relief rate between HRD(+ ) group and HRD(-) group [66.7% (12/18) vs. 44.4% (4/9), P=0.411]. The incidence of at least one hematological adverse event during radium-223 treatment in the HRD(+ ) group was higher than that in the HRD(-) group [77.8% (14/18) vs. 33.3% (3/9), P=0.039]. There was no significant difference in the incidence of grade 1-2 hematological adverse events between the two groups [72.2%(13/18) vs. 33.3%(3/9), P=0.097]. Only 1 patient in the HRD(+ ) group experienced grade 3 anemia during treatment which was recovered after blood transfusion. Conclusions:Compared to mCRPC patients without HRR gene mutation, patients with HRR gene mutations had better ALP response and bone pain relief after radium-223 treatment. The overall incidence of adverse events in the HRD(+ ) group is higher than that in HRD(-) group, and there was no significant difference in grade 1-2 hematological adverse events between the two goups. It is necessary to expand the sample size to further verify the conclusion.

Platinum in neoadjuvant therapy for triple-negative breast cancer / 中华内分泌外科杂志

Although adding platinum to taxane- and anthracycline-based neoadjuvant chemotherapy regimens for triple-negative breast cancer (TNBC) patients can significantly improve the pathological complete response (pCR) rate and long-term survival, it is associated with higher treatment-related adverse events (AEs) . Current researches focus on the response predictors to select patients who may benefit from platinum-based chemotherapy. Homologous recombination deficiency (HRD) can identify patients who truly need platinum drugs, that is, those with BRCA wild-type but HRD tumors. Results suggest that anthracycline-based chemotherapy is sufficient for BRCA mutation carriers and that non-HRD carriers will not benefit from the added carboplatin.

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.

Progress of poly (adenosine diphosphate-ribose) polymerase inhibitors in treatment of colorectal cancer / 肿瘤研究与临床

Colorectal cancer is one of the most common malignant tumors, and its morbidity and mortality increase year by year. In recent years, some patients with colorectal cancer have benefited from precision targeted therapies, but the overall prognosis is still unsatisfactory. Treatment of homologous recombination deficiency represented by BRCA1/2 has become a hot research direction at present. With the wide application and exact curative effect of poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitors in ovarian cancer, breast cancer, pancreatic cancer and other malignant tumors, PARP inhibitors are also gradually being used in colorectal cancer. This review summarizes the current research progress of PARP inhibitors in treatment of colorectal cancer.

MiR-375-3p enhanced radiosensitivity of colorectal cancer cells by inhibiting homologous recombination repair of DSBs / 中华放射医学与防护杂志

Objective:To investigate the effect of miR-375-3p on DNA damage repair and radioresistance of colorectal cancer cells.Methods:After overexpression of miR-375-3p in HCT116 and HT29, cell proliferation ability was detected by CCK-8 assay, clone formation ability was detected by clone formation assay, apoptosis was detected by Annexin V-FITC/PI double staining method and cell cycle distribution was detected by flow cytometry, and the formation of γ-H2AX foci were used to analyze homologous recombination (HR) repair efficiency. Bioinformatics was used to predict the downstream target genes of miR-375-3p in the HR repair pathway. A dual luciferase reporter gene assay was used to validate the regulation effect of miR-375-3p on Rad51 gene. The expression of miR-375-3p in HCT116 cells irradiated with 60Co γ-rays at 2 and 6 Gy was measured by RT-qPCR. The inhibition effect of miR-375-3p on the radiosensitivity of HCT116 cells was analyzed after irradiation with different doses of 0, 1, 2, 4 and 6 Gy. Results:Overexpression of miR-375-3p inhibited the proliferation and colony formation ability, induced G1 phase cycle arrest and cell apoptosis of colorectal cancer cells, enhanced DSBs formation, inhibited Rad51 expression, and significantly decreased HR repair efficiency ( t = 10.055, P < 0.05). Dual luciferase reporter gene assay demonstrated that miR-375-3p bound to Rad51 3′UTR region ( t = 5.013, P< 0.05). In addition, irradiation increased miR-375-3p expression, and inhibition of miR-375-3p expression reduced radiosensitivity of colorectal cancer cells ( t=6.460, 5.619, 10.150, P<0.05). Conclusions:miR-375-3p inhibited the homologous recombination repair efficiency of DSBs and enhanced the radiosensitivity of colorectal cancer cells.

Expression of DNA damage-binding protein 1 in hepatocellular carcinoma tissues and its effect on homologous recombination repair and targeted killing in SMMC-7721 cells / 肿瘤研究与临床

Objective:To investigate the expression of DNA damage repair factor DNA damage-binding protein 1 (DDB1) in hepatocellular carcinoma tissues, and the effect of DDB1 gene silencing on DNA repair and targeted killing in human hepatocellular carcinoma SMMC-7721 cells.Methods:The UALCAN platform was used to perform bioinformatics analysis on the expression of DDB1 in hepatocellular carcinoma tissues (371 cases) and paracancerous tissues (50 cases) in The Cancer Genome Atlas (TCGA) database and the correlation of DDB1 expression with the overall survival of liver cancer patients were analyzed by bioinformatics using the UALCAN platform. SMMC-7721 cells were transfected with small interfering RNA (siRNA) targeting DDB1 and negative control siRNA, which were DDB1 silencing group and negative control group, respectively. X-ray irradiation induced exogenous DNA double strand break (DSB) damage in the two groups of cells. Immunofluorescence staining (γH2AX was used for assessing cellular DSB damage, RPA32s33 and Rad51 were used for assessing homologous recombination repair) and Western blotting (were used to detect the level of RPA32s33 protein) were used to analyze the effect of DDB1 gene silencing on DSB damage repair. Sister chromosome exchange (SCE) experiment was used to analyze the frequency of SCE of homologous recombination of cells in DDB1 silencing group and negative control group. Tetramethylazozolium salt (MTT) method was used to analyze the killing effect of PARP inhibitor olapani (10 μmol/L), cisplatin (1 μg/ml) and olapani combined with cisplatin on SMMC-7721 cells in DDB1 silencing group and negative control group.Results:Bioinformatics analysis showed that the level of DDB1 mRNA in liver cancer tissues was higher than that in paracancerous tissues ( P < 0.001), and the overall survival of patients with high expression of DDB1 was worse than that of patients with low expression of DDB1 ( P = 0.029). When cultured for 4 hours after X-ray irradiation, the number of γH2AX foci in cells of the negative control group had mostly disappeared, and there were still more cells in DDB1 silencing group [(5.1±2.0) per cell vs. (13.4±2.0) per cell, t = -5.08, P = 0.007]. When cultured for 4 hours after X-ray irradiation, the number of RPA32s33 foci in the negative control group [(30.8±5.0) per cell vs. (13.2±1.6) per cell] and the number of Rad51 foci [(19.5±1.8) per cell vs. (8.3±3.3) per cell] were higher than those in the DDB1 silencing group, and the differences between the two groups were statistically significant (both P < 0.01). The frequency of SCE in the negative control group was higher than that in the DDB1 silencing group [(21.2±3.0)% vs. (11.2±1.6)%, t = 5.07, P = 0.007]. MTT assay showed that after olaparib treatment, the survival rate of cells in the DDB1 silencing group was lower than that in the negative control group [(40.3±3.6)% vs. (79.8±1.3)%, t = 17.94, P < 0.001]. When treated with olapani combined with cisplatin, the survival rate of cells in the two groups further decreased, and the survival rate of cells in the DDB1 silencing group was lower than that in the negative control group [(10.2±2.8)% vs. (29.6±3.4)%, t = 7.72, P = 0.002]. When treated with cisplatin alone, there was no significant difference in cell survival between DDB1 silencing group and negative control group [(41.9±5.1)% vs. (49.8±3.3)%, t = 2.71, P = 0.054]. Conclusions:The high expression of DDB1 in hepatocellular carcinoma tissues may be an important factor in the treatment resistance and poor prognosis of hepatocellular carcinoma. Knockdown of DDB1 gene expression can promote the sensitivity of SMMC-7721 cells to PARP inhibitors, and its mechanism may be related to the homologous recombination repair defect of SMMC-7721 cells caused by DDB1 silencing.

Construction of hypervirulent Klebsiella pneumoniae strain with hfq gene deletion and study on its biological characteristics / 中华微生物学和免疫学杂志

Objective:To construct a mutant strain of hypervirulent Klebsiella pneumoniae NTHU-K2044 with hfq gene deletion and to analyze its biological characteristics. Methods:The hfq gene of NTUH-K2044 was knocked out by homologous recombination technology to construct △ hfq mutant strain. Its biological characteristics including growth rate, environmental stress tolerance, biofilm formation, capsular polysaccharide synthesis, resistance to neutrophil phagocytosis and lethality to Galleria mellonella larvae were analyzed by comparing with the wild-type strain using phenotypic experiments. Results:The △ hfq mutant strain of hypervirulent Klebsiella pneumoniae NTHU-K2044 was successfully constructed. Phenotypic experiments showed that the △ hfq mutant strain had significantly slower growth rate, smaller colonies and decreased hypermucoviscosity. Its growth was significantly inhibited under different environmental stress conditions such as pH9, pH5.5, 0.7 mmol/L SDS, 5% NaCl, 0.1% H 2O 2 and high temperature of 50℃. In terms of virulence and pathogenicity, the △ hfq mutant strain showed decreased ability to form biofilm and capsule, significantly down-regulated expression of magA and rmpA genes required for capsule synthesis, lower survival rate in the neutrophil bactericidal test and obviously reduced lethality to Galleria mellonella larvae. Conclusions:As a RNA chaperone, Hfq protein could participate in post-transcriptional regulation and play an important role in regulating the physiology, environmental adaptability and virulence of hypervirulent Klebsiella pneumoniae. This study provided reference for further study on hypervirulent Klebsiella pneumoniae.

DNA damage repair promotion in colonic epithelial cells by andrographolide downregulated cGAS‒STING pathway activation and contributed to the relief of CPT-11-induced intestinal mucositis

Gastrointestinal mucositis is one of the most debilitating side effects of the chemotherapeutic agent irinotecan (CPT-11). Andrographolide, a natural bicyclic diterpenoid lactone, has been reported to possess anti-colitis activity. In this study, andrographolide treatment was found to significantly relieve CPT-11-induced colitis in tumor-bearing mice without decreasing the tumor suppression effect of CPT-11. CPT-11 causes DNA damage and the release of double-stranded DNA (dsDNA) from the intestine, leading to cyclic-GMP-AMP synthase (cGAS)‒stimulator of interferon genes (STING)-mediated colitis, which was significantly decreased by andrographolide both in vivo and in vitro. Mechanistic studies revealed that andrographolide could promote homologous recombination (HR) repair and downregulate dsDNA‒cGAS‒STING signaling and contribute to the improvement of CPT-11-induced gastrointestinal mucositis. These results suggest that andrographolide may be a novel agent to relieve gastrointestinal mucositis caused by CPT-11.

Construction of the hit-deficient mutant strain of Streptococcus mutans ATCC25175 / 口腔疾病防治

Objective@#To construct a hit-deficient mutant strain of S. mutans ATCC25175 and verify its cell cycle regulatory function.@*Method @# Genomic DNA was extracted from S. mutans ATCC25175 strains, and then the upstream and downstream DNA fragments of the hit gene were cloned into the pFW5 vector (spectinomycin resistant) to construct recombinant plasmids using PCR amplification. Third, employed by natural genetic transformation in S. mutans ATCC25175 strains, the linearized recombinant plasmids were transformed into their genetic competence, induced by the synthesized competence-stimulating peptide (CSP), and then, homologous recombination was utilized to produce crossover and noncrossover products. Fourth, the hit-deficient mutant strains of S. mutans ATCC25175 were screened through the spectinomycin-resistance marker and identified by the electrophoresis of PCR products and PCR Sanger sequencing. Finally, its growth rate in vegetative BHI medium was also investigated.@* Results @# The upstream (856 bp) and downstream (519 bp) DNA fragments of the hit gene from the genomic DNA materials of S. mutans ATCC25175 were cloned into two multiple cloning sites (MCS-I and MCS-II) of the pFW5 vector, respectively, and the recombinant plasmid pFW5_hit_Up_Down was constructed and identified by double-emzyme digestion and PCR Sanger sequencing. The linearized recombinant plasmids were transformed into their genetic competence, induced by the synthetic CSP, and then, homologous recombination was utilized to produce various products. The hit-deficient mutant strains of S. mutans ATCC25175 were screened through the spectinomycin resistance marker and identified by the electrophoresis of PCR products and Sanger sequencing. The growth rate of the hit-deficient mutant strains versus their parental S. mutans ATCC25175 strains was increased greatly (P<0.001).@* Conclusion@# The hit-deficient mutant strains of S. mutans ATCC25175, having heritable traits, were successfully constructed, and the encoding Hit protein is growth-phase regulated in the cell cycle.

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

Comprehensive functional annotation of susceptibility variants identifies genetic heterogeneity between lung adenocarcinoma and squamous cell carcinoma / 医学前沿

Although genome-wide association studies have identified more than eighty genetic variants associated with non-small cell lung cancer (NSCLC) risk, biological mechanisms of these variants remain largely unknown. By integrating a large-scale genotype data of 15 581 lung adenocarcinoma (AD) cases, 8350 squamous cell carcinoma (SqCC) cases, and 27 355 controls, as well as multiple transcriptome and epigenomic databases, we conducted histology-specific meta-analyses and functional annotations of both reported and novel susceptibility variants. We identified 3064 credible risk variants for NSCLC, which were overrepresented in enhancer-like and promoter-like histone modification peaks as well as DNase I hypersensitive sites. Transcription factor enrichment analysis revealed that USF1 was AD-specific while CREB1 was SqCC-specific. Functional annotation and gene-based analysis implicated 894 target genes, including 274 specifics for AD and 123 for SqCC, which were overrepresented in somatic driver genes (ER = 1.95, P = 0.005). Pathway enrichment analysis and Gene-Set Enrichment Analysis revealed that AD genes were primarily involved in immune-related pathways, while SqCC genes were homologous recombination deficiency related. Our results illustrate the molecular basis of both well-studied and new susceptibility loci of NSCLC, providing not only novel insights into the genetic heterogeneity between AD and SqCC but also a set of plausible gene targets for post-GWAS functional experiments.

A rapid and accurate method for herpesviral gnome editing / 生物工程学报

To rapidly and accurately manipulate genome such as gene deletion, insertion and site mutation, the whole genome of a very virulent strain Md5 of Marek's disease virus (MDV) was inserted into bacterial artificial chromosome (BAC) through homogeneous recombination. The recombinant DNA was electroporated into DH10B competent cells and identified by PCR and restriction fragment length polymorphism analysis. An infectious clone of Md5BAC was obtained following transfection into chicken embryo fibroblast (CEF) cells. Furthermore, a lorf10 deletion mutant was constructed by two step Red-mediated homologous recombination. To confirm the specific role of gene deletion, the lorf10 was reinserted into the original site of MDV genome to make a revertant strain. All the constructs were rescued by transfection into CEF cells, respectively. The successful packaging of recombinant viruses was confirmed by indirect immunofluorescence assay. The results of growth kinetics assay and plaques area measurement showed that the lorf10 is dispensable for MDV propagation in vitro. Overall, this study successfully constructed an infectious BAC clone of MDV and demonstrated its application in genome manipulation; the knowledge gained from our study could be further applied to other hepesviruses.

Research progress in targeting homologous recombination repair for tumor therapy / 药学学报

Applying poly(ADP-ribose) polymerase inhibitors (PARPi) to the treatment of cancers with homologous recombination deficiency (HRDness) has been a great advance in the field of molecular therapeutics. However, in the clinic patients lacking the specific mutations or developing reverse mutations in the process of PARPi treatment may not benefit from PARPi monotherapy. Therefore, targeting homologous recombination (HR) repair with molecularly targeted agents is becoming an attractive research focus and is raising the concept of "chemical HRDness". HR repair is an evolutionarily conserved and extensively regulated process that employs sister chromatids as the template to repair DNA double-strand breaks with high fidelity. In addition to directly targeting HR components, modulation of regulatory pathways controlling HR repair is effective in achieving the "HRDness" phenotype; this includes modulation of the cell cycle checkpoint regulatory pathway, the phosphatidylinositol 3-kinase (PI3K) signaling pathway, the chromatin remodeling pathway, etc. Targeting HR repair can not only result in "synthetic lethality" when combined with PARPi, but also sensitizes cancers to traditional radio/chemotherapy and novel immunotherapy. In this review we describe the HR repair pathway and its regulatory pathways, summarize the preclinical and clinical outcomes of targeting HR repair, discuss the remaining problems in this field and provide a prospective on its application in tumor therapy.

Construction of rat diacylglycerol kinase gamma lentivirus overexpression vector by homologous recombination / 中国组织工程研究

BACKGROUND: Lentiviral vectors have been widely used as exogenous transgenic vectors. However, a recombinant lentiviral vector containing rat diacylglycerol kinase y (DGKy) gene has not been reported. OBJECTIVE: To construct lentiviral overexpression vector of rat DGKy by homologous recombination. METHODS: Total RNA was extracted from the brain tissue of adult Sprague-Dawley rats, and the cDNA obtained by PCR was used as a template to amplify the 5'-end 1 029 bp and the 3'-end 1 362 bp of the rat DGKy gene CDS. Then, the two homologous recombination fragments were ligated into the plasmid vector. The positive clones were confirmed by PCR and DNA sequencing. The CMV-rat DGKy-GFP lentiviral vector and the lentiviral packaging system were co-transfected into 293T cells for virus packaging and lentivirus was collected to infect 293T cells. The expression of GFP in infected 293T cells was observed under fluorescence microscope. Real-time PCR and western blot assay were used to detect the relative expression of DGKy mRNA in infected 293T cells. RESULTS AND CONCLUSION: The results of PCR simplification and sequencing indicated that the CMV-rat DGKy-GFP lentiviral vector was successfully constructed. In 293T cells infected with CMV-rat DGKy-GFP lentivirus, the expression of GFP was observed under fluorescence microscope and the DGKy mRNA expression was increased significantly than that of the vector group by real-time PCR (P < 0.01). Western blot assay results showed that the DGKy protein expression of the selected GFP-positive 293T cells was increased very significantly (P < 0.001). To conclude, the rat DGKy lentiviral overexpression vector has been successfully constructed and maintains high expression in 293T cells.

Advances in gene editing of Corynebacterium glutamate / 生物工程学报

Corynebacterium glutamicum, an important microorganism to produce amino acids and organic acids, has been widely applied in food and medicine fields. Therefore, using editing tools to study the function of unknown genes in C. glutamicum has great significance for systematic development of industrial strain with efficient and novel production capability. Recently, gene editing has been greatly developed. Traditional gene editing based on homologous recombination and gene editing mediated by nuclease are successfully applied in C. glutamicum. Among these, the CRISPR system has been developed to be a main tool used for gene knockout of C. glutamicum due to its advantages of efficiency, simplicity and good target specificity. However, more efficient and reliable knockout system is still urgently demanded, to help develop high-performing strains in industrial application.

Maintenance of pegylated liposomal doxorubicin/carboplatin in patients with advanced ovarian cancer: randomized study of an Asian Gynecologic Oncology Group / 부인종양

Generation and evaluation of a recombinant myxomavirus expressing the VP60 protein of rabbit haemorrhagic disease virus / 生物工程学报

Rabbit haemorrhagic disease virus (RHDV) and myxoma virus (MYXV), are two pathogens that have harmful effect on rabbit breeding and population decline of European rabbits in their native range, causing rabbit haemorrhagic disease (rabbit fever) and myxomatosis, respectively. The capsid protein VP60 of the RHDV represents the major antigenic protein. To develop a recombinant bivalent vaccine candidate that can simultaneously prevent these two diseases, we used the nonessential gene TK (thymidine kinase) of MYXV as the insertion site to construct a recombinant shuttle vector p7.5-VP60-GFP expressing the RHDV major capsid protein (VP60) and the selectable marker GFP. Then the shuttle vector p7.5-VP60-GFP was transfected into rabbit kidney cell line RK13 which was previously infected with MYXV. After homologous recombination, the recombinant virus expressing GFP was screened under a fluorescence microscope and named as rMV-VP60-GFP. Finally, the specific gene-knock in and expression verification of the vp60 and gfp genes of the recombinant virus was confirmed by PCR and Western blotting. The results showed that these two genes were readily knocked into the MYXV genome and also successfully expressed, indicating that the recombinant MYXV expressing the vp60 of RHDV was generated. Protection against MYXV challenge showed that the recombinant virus induced detectable antibodies against MYXV which would shed light on development of the effective vaccine.