Microsatellite instability and expression of DNA mismatch repair genes in malignant astrocytic tumors from adult and pediatric patients

Microsatellite instability (MSI) is used as a molecular marker for defective DNA mismatch repair (MMR) genes.We report here alterations of MSI in 15 malignant astrocytomas (WHO grade Ⅲ) and glioblastomas (GBM; WHO grade Ⅳ) of pediatric patients (2-21 years) and 12 GBM from adults (44-68 years) by comparative analysis of BAT25/BAT26 loci and 10 other microsatellite markers. High-level microsatellite instability (MSI-H) occurred in 4 of the 15 pediatric cases (26.7%) and in 1 of the 12 adult GBM cases (8.3%). Low-level mi-

THE ABNORMAL EXPRESSION OF CLONED REPEATED SEQUENCE DNA, L5B-4, IN RAT HEPATOMA BERH-2

A repeated sequence DNA fragment, L5B-4, was cloned from the 5 kb BamHI DNA fragments of rat genomic DNA. The expressions of the L5B-4 DNA fragment are different in liver and hepatoma cells. The amounts of transcripts in hepatoma cells are lower in nucleus and higher in cytoplasm, especially in polysomal RNA, as compared with that in liver cells. The alteration shown in polysomal RNA of hepatoma cells seems to be specific. These results are discussed with respect to the possible function of this repeated DNA and its variation in hepatoma cells.

Amplification and function analysis of N6-adenine-specific DNA methyltransferase gene in Nilaparvata lugens

Methylation of the N6 position of adenine, termed N6-methyladenine, protects DNA from restriction endonucleases via the host-specific restriction-modification system. N6-methyladenine was discovered and has been well studied in bacteria. N6-adenine-specific DNA methyltransferase（N6AMT） is the main enzyme catalyzing the methylation of the adenine base and knowledge of this enzyme was mainly derived from work in prokaryotic models. However, large-scale gene discovery at the genome level in many model organisms indicated that the N6AMT gene also exists in eukaryotes, such as humans, mice, fruit flies and plants. Here, we cloned a N6AMT gene from Nilaparvata lugens（Nlu-N6AMT） and amplified its fulllength transcript. Then, we carried out a systematic investigation of N6AMT in 33 publically available insect genomes, indicating that all studied insects had N6AMT. Genomic structure analysis showed that insect N6AMT has short introns compared with the mammalian homologs. Domain and phylogenetic analysis indicated that insect N6AMT had a conserved N6-adenine Mlase domain that is specific to catalyze the adenine methylation. Nlu-N6AMT was highly expressed in the adult female. We knocked down Nlu-N6AMT by feeding ds RNA from the second instar nymph to adult female, inducing retard development of adult female. In all, we provide the first genome-wide analysis of N6AMT in insects and presented the experimental evidence that N6AMT might have important functions in reproductive development and ovary maturation.

Inhibition of HBV Replication by Delivering the Dual-gene Expression Vector pHsa-miR16-siRNA in HepG2.2.15 Cells

This study aimed to construct the dual-gene expression vector p Hsa-miR16-siRNA which can express human miR-16 and HBV X siRNA, and examine its regulatory effect on HBV gene expression in the HepG2.2.15 cell line. The expression vectors siR-1583 and pHsa-miR16-siRNA were designed and constructed. Hep G2.2.15 cells were transfected with the empty vector, siR-1583, pmiR-16 and pHsa-miR16-siRNA, respectively. ELISA was performed to measure the expression of HBsAg and HBeAg in the culture supernatant 48 and72 h post transfection. Fluorescence quantitative PCR was used to measure the HBV mRNA degradation efficiency and HBV DNA copy number. The results showed that the expression of HBV genes was significantly inhibited in Hep G2.2.15 cells transfected with siR-1583, pmiR-16 and pHsa-miR16-siRNA, respectively, when compared with that in cells transfected with the empty vectors, with the inhibitory effect of pHsa-miR16-siRNA being the most significant. ELISA showed that the inhibitory rates of HBs Ag and HBeAg in pHsa-miR16-siRNA transfected cells were correspondingly 87.3% and 85.0% at 48 h, and 88.6% and 86.5% at 72 h post transfection（P〈0.01 vs. control group）. RT-PCR showed that the level of HBV mRNA decreased by 80.2%（t=–99.22, P〈0.01）, the genomic HBV DNA by 92.8%（t=–73.06, P〈0.01）, and the supernatant of HBV DNA copy number by 89.8%（t=–47.13, P〈0.01） in pHsa-miR16-siRNA transfected group. It was suggested that the dual-gene expression vector pHsa-miR16-siRNA can inhibit the replication of HBV more efficiently than a single-gene expression vector.

Expression and semi-quantification of hepatitis B virus reverse transcriptase protein in a prokaryotic system

The reverse transcriptase （RT） protein of hepatitis B virus （HBV） has been successfully expressed by recombinant technology in Eschericahia coli （ E. coli ）. In this study we aimed to develop a semi-quantitative assay for the study of HBV RT protein using this system. Complete HBV polymerase gene from a wild type virus （rt306P） and the polymerase gene from a mutant, with rt306P substituted by serine （rtP306S） were separately fused to the maltose binding protein （MBP） gene and expressed in E. coli respectively. The expression levels of HBV polymerase genes from the wild type virus and its counterpart mutant at rt306 were compared. When these proteins were semi-quantified by Westem blotting using rabbit anti-TP serum, the rtP306S mutant showed decreased expression of MBP-HBV polymerase. By this method, we have shown that the expression level of HBV RT could be affected by substitutions in its amino acid sequences, and this method could be used to study the characteristics of HBV RT protein.

p21^(WAF1/CIP1) gene DNA sequencing and its expression in human osteosarcoma

Background Mutation and expression change of p21 WAF1/CIP1 may play a role in the growth of osteosarcoma. This study was to investigate the expression of the p21 WAF1/CIP1 gene in human osteosarcoma,p21 WAF1/CIP1 gene DNA sequence change and their relationships with the phenotype and clinical prognosis.Methods p21 WAF1/CIP1 gene in 10 normal people and the tumours of 45 osteosarcoma patients were examined using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) with silver staining. The PCR product with an abnormal strand was sequenced directly. The p21 WAF1/CIP1 gene mRNA and P21 protein of 45 cases of osteosarcoma were investigated by using in situ hybridization and immunohistochemistry,respectively. Results The occurrence of P21 protein in osteosarcoma was 17.78% (8/45),and p21 WAF1/CIP1 mRNA expression in osteosarcoma was 42.22% (19/45). The p21 WAF1/CIP1 gene DNA sequencing of amplified production showed that in p21 WAF1/CIP1 gene exon 3 of 36 cases of human osteosarcoma,there were 17 cases (47.22%) with C→T at position 609; 10 normal blood samples’ DNA sequence analysis yielded 8 cases (80.00%) with C→T at the same position. Conclusions Along with the increase of malignancy,the expression of p21 WAF1/CIP1 mRNA and P21 protein in osteosarcoma tends to decrease. It is uncommon for the p21 WAF1/CIP1 gene mutation to occur in human osteosarcoma. As a result, the possible existence of tumour subtypes of p21 WAF1/CIP1 gene mutation should be investigated. Our research leads to the location of p21 WAF1/CIP1 gene polymorphism of Chinese osteosarcoma patients,which can provide a basis for further research.

两种纯化试剂盒对人体脱落细胞检材STR检出率比较

随着DNA检验技术的普及和发展,办案人员应用DNA技术的意识不断增强,采集人体脱落细胞进行DNA分析应用逐渐广泛。采用常规提取方法难以获得高质量的DNA模板,影响后续的STR分型。

5-aza-2'-deoxycitydine induces demethylation and up-regulates transcription of p16^(INK4A) gene in human gastric cancer cell lines

Background To investigate the effects of DNA methylation on the expression of tumor-associated genes and the cell cycle in human gastric cancer cells. Methods Two gastric cancer cell lines (MKN-45 and HGC-27) were treated with DNA methyltransferase (DNMT) inhibitor,5-aza-2’-deoxycytidine (5-aza-dC). The expressions of p16 INK4A,p21 WAF1,p53 , p73 ,c-Ha-ras and c-myc genes mRNA were detected by using reverse transcription PCR (RT-PCR). DNA methylation status of p16 INK4A gene promoter was assayed by bisulfite modification and sequencing. The cell cycle was analyzed by using flow cytometry (FCM). Results 5-aza-dC induced the demethylation of p16 INK4A gene promoter. The expression of p16 INK4A mRNA was obviously up-regulated by treatment with 10 μmol/L (MKN-45 cells) or 5 μmol/L (HGC-27 cells) of 5-aza-dC for 24 hours. However,5-aza-dC treatment failed to regulate the expressions of p21 WAF1,p53 , p73 ,c-Ha-ras and c-myc genes in MKN-45 and HGC-27 cells. Furthermore,5-aza-dC induced the cell cycle arrest in G1 phase in HGC-27 cell,but not in MKN-45 cell. Conclusions DNA methylation regulates the transcription of p16 INK4A but not p21 WAF1 and proto-oncogenes in human gastric cancer cell lines MKN-45 and HGC-27.