Objective: To establish a reformative detection system which has sound ability of providing information on molecular mutagenesis spectrum and the specificity of detection system of repackaged λ phage. Methods: LacZ g...Objective: To establish a reformative detection system which has sound ability of providing information on molecular mutagenesis spectrum and the specificity of detection system of repackaged λ phage. Methods: LacZ gene, as mutational target gene and reporter gene, was applied into the detection system. The λ gt11 DNA treated with ENU (1-ethyl-1-nitrosourea) and 9-AA (9-aminoacridine) was repackaged in vitro. The packaged λ phage was then grown in E. coli Y1090 on a selective plate containing X-gel and IPTG. The survival and mutation frequencies were determined by counting the clear-plaque and blue-plaque, and the molecular mutation mechanism was studied by extracting and sequencing the LacZ gene of mutants. Results: The survival of repackaged λ phages treated with 9-AA and ENU apparently decreased in consistent dose-dependence. The mutation frequency of clear-plaque mutants showed a linear dose-related increase. The predominant mutations induced by 9-AA were ± 1 frameshift mutation, and 9-AA induced - 1 frameshift was much more effective than induced +1 frameshift. 9-AA also induced substitutions with transversions more common. ENU-induced mutations were chiefly occurred at G: C sites. Substitutions induced by ENU were mainly G: C→A: T, G: C→C: G and A: T→T: A transversion. Conclusion: Mutation detection system of λgt11 DNA containing LacZ gene is proven better than that of λDNA without LacZ gene. The combination of survival, mutant frequency and sequence spectrum can not only increase the sensitivity and specificity of the new method, but also provide a better understanding of the molecular mechanism of mutation for ultimate extrapolation to risk assessment.展开更多
Objective To construct a λgt11 cDNA expression library of Echinococcus multilocularis protoscolex isolated in China. Methods Echinococcus multilocularis protoscolex mRNA was extracted using a Quickprep MicromRNA pu...Objective To construct a λgt11 cDNA expression library of Echinococcus multilocularis protoscolex isolated in China. Methods Echinococcus multilocularis protoscolex mRNA was extracted using a Quickprep MicromRNA purification kit based on combining of the disruptive and protective properties of guanidinium thiocyanate (GTC) with the speed and selectivity of oligo (dT)-cellulose chromatography in a spum-column with some modification. Purified mRNA (1.8 μg) was submitted to reverse transcription using random hexamers ［pd(N6)］. The double-strand blunt-ended cDNAs were ligated with an EcoRI/NotI adaptor to form a cohesive EcoRI end. Subsequently the synthesized cDNA was inserted into vector λgt11 EcoRI arms. After being packaged in vitro, λgt11 was put to an infectious bacteria Echinococcus coli (E.coli) strain Y1090; the recombinants were screened by color selection. PCR amplification was performed to evaluate the size of insertion DNA fragments.Results The recombinant ratio was nearly 100% and approximately 1×106 clones could be derived from this λgt11 cDNA library. PCR results indicated that the insertion DNAs were about 1.48 kb. Conclusions A λgt11 cDNA expression library consisting of a million recombinant clones has been constructed from Echinococcus multicularis protoscolex mRNA. Further studies on this library are deserved.展开更多
基金National Science Foundation of China (NS-FC:No: 3880680 No: 39670643)
文摘Objective: To establish a reformative detection system which has sound ability of providing information on molecular mutagenesis spectrum and the specificity of detection system of repackaged λ phage. Methods: LacZ gene, as mutational target gene and reporter gene, was applied into the detection system. The λ gt11 DNA treated with ENU (1-ethyl-1-nitrosourea) and 9-AA (9-aminoacridine) was repackaged in vitro. The packaged λ phage was then grown in E. coli Y1090 on a selective plate containing X-gel and IPTG. The survival and mutation frequencies were determined by counting the clear-plaque and blue-plaque, and the molecular mutation mechanism was studied by extracting and sequencing the LacZ gene of mutants. Results: The survival of repackaged λ phages treated with 9-AA and ENU apparently decreased in consistent dose-dependence. The mutation frequency of clear-plaque mutants showed a linear dose-related increase. The predominant mutations induced by 9-AA were ± 1 frameshift mutation, and 9-AA induced - 1 frameshift was much more effective than induced +1 frameshift. 9-AA also induced substitutions with transversions more common. ENU-induced mutations were chiefly occurred at G: C sites. Substitutions induced by ENU were mainly G: C→A: T, G: C→C: G and A: T→T: A transversion. Conclusion: Mutation detection system of λgt11 DNA containing LacZ gene is proven better than that of λDNA without LacZ gene. The combination of survival, mutant frequency and sequence spectrum can not only increase the sensitivity and specificity of the new method, but also provide a better understanding of the molecular mechanism of mutation for ultimate extrapolation to risk assessment.
文摘Objective To construct a λgt11 cDNA expression library of Echinococcus multilocularis protoscolex isolated in China. Methods Echinococcus multilocularis protoscolex mRNA was extracted using a Quickprep MicromRNA purification kit based on combining of the disruptive and protective properties of guanidinium thiocyanate (GTC) with the speed and selectivity of oligo (dT)-cellulose chromatography in a spum-column with some modification. Purified mRNA (1.8 μg) was submitted to reverse transcription using random hexamers ［pd(N6)］. The double-strand blunt-ended cDNAs were ligated with an EcoRI/NotI adaptor to form a cohesive EcoRI end. Subsequently the synthesized cDNA was inserted into vector λgt11 EcoRI arms. After being packaged in vitro, λgt11 was put to an infectious bacteria Echinococcus coli (E.coli) strain Y1090; the recombinants were screened by color selection. PCR amplification was performed to evaluate the size of insertion DNA fragments.Results The recombinant ratio was nearly 100% and approximately 1×106 clones could be derived from this λgt11 cDNA library. PCR results indicated that the insertion DNAs were about 1.48 kb. Conclusions A λgt11 cDNA expression library consisting of a million recombinant clones has been constructed from Echinococcus multicularis protoscolex mRNA. Further studies on this library are deserved.
