Drosophila RecQ5 is required for efficient SSA repair and suppression of LOH in vivo

RecQ5 in mammalian cells has been suggested to suppress inappropriate homologous recombination. However, the specific pathway(s) in which it is involved and the underlining mechanism(s) remain poorly understood. We took advantage of genetic tools in Drosophila to investigate how Drosophila RecQ5 (dRecQ5) functions in vivo in homologous recombination-mediated double strand break (DSB) repair. We generated null alleles of dRecQ5 using the targeted recombination technique. The mutant animals are homozygous viable, but with growth retardation during development. The mutants are sensitive to both exogenous DSB-inducing treatment, such as gamma-irradiation, and endogenously induced double strand breaks (DSBs) by I-Sce I endonuclease. In the absence of dRecQ5, single strand annealing (SSA)-mediated DSB repair is compromised with compensatory increases in either inter-homologous gene conversion, or non-homologous end joining (NHEJ) when inter-chromosomal homologous sequence is unavailable. Loss of function of dRecQ5 also leads to genome instability in loss of heterozygosity (LOH) assays. Together, our data demonstrate that dRecQ5 functions in SSA-mediated DSB repair to achieve its full efficiency and in suppression of LOH in Drosophila.

Detection of Legionella pneumophila infection in children with lower respiratory infections by ELISA and PCR / 中华急诊医学杂志

Objective To investigate the infection rate of Legionella pneumophila(LP)in children younger than 5 years with lower respiratory infections by ELISA and PCR.Method Serum LP-IgM and IgG were measured by ELISA,and LP DNA in sputum or throat swab were detected by PCR in 300 children less than 5 years with lower respiratory infections.The data were analyzed by chi-square test and the consistency of the two methods was analyzea by NcNemar test.Results Serum antibody detected by ELISA was positive in 17 cases(5.67%),including 10 positive of IgM and 7 positiile of lgG.In these 17 eases,11 were males and 6 were females with similar positive rates(5.76%vs 5.5%).Four cases(2.53%)were positive in children aged from 27 days to 1 year,while 7(7.37%)and 6 cases(12.77%)were positive in children aged 1-3 years and 3-5 years,respectively.Seven cases(5.19%)found in the winter and spring seasons and 10 cases(6.06%)in summer and autumn seasons.Eleven children(11.83%)were from urban area and only 6(2.9%)from countryside.DNA in sputum or throat swab detected by PCR was positive in 16 cases(5.33%),included 10 males and 6 females with similar positive rates(5.24%vs 5.5%).Five cases(3.16%)were positive in children aged from 27 days to 1 year,while 6(6.32%)and 5 cases(10.64%)were positive in children aged 1-3 years and 3-5 years,respectively.Three cases(2.22%)found in the winter and spring seasons and 13 cases(7.88%)in sunmmr and alltumll seasons.Nine children(9.68%)were from urban area and only 7(3.38%)from countryside.McNemar test was used to compare the data of ELISA and PCR results with a Qm of 0.037 and a Pr of 0.8474.Conclusions LP might contribute partly to the lower respiratory infections in children less than 5 years.The infection rate of LP increases with age increasing.Urban children have a higher infection rate than those living in countryside.Both methods have a good consistency.

Glycoprotein B genotype of human cytomegalovirus analysis by nPCR-RFLP / 中华传染病杂志

Objective Aim to set up the method of glycoprotein B genotype of human cytomegalovirus (HCMV) analysis by using nested polymerase chain reaction(nPCR) and restriction fragment length polymorphism(RFLP). Methods Eleven blood samples and twenty-three urine samples were obtained from thirty-four HCMV-infected patients. A fragment of gB gene was amplified by nPCR. HCMV gB genotyping was carried out by RFLP, and the amplified DNA fragments were verified by DNA sequencing. Results Of the 34 patients, gB type Ⅰ was found in 13 patients, gB type Ⅱ in 12 patients, gB type Ⅲ in 9 patients, and none had the gB type Ⅳ sequence. The similarities of PCR products of HCMV gB Ⅰ, Ⅱ and Ⅲ amplified compared with the sequences of prototype strains in GenBank were 98.1%～99.6%, 98.9%～100%, 97.3%～98.9%. Conclusions The nPCR assay developed in this study was sensitive and specific for detection of HCMV, and RFLP analysis of HCMV gB genotype was definite and reliable.