title: [Expression detection and location analysis of BstNI isoschizomer restriction-modification system gene].
abstract: Some genetic markers of E. coli HB101 and JM110 were identified, two bacterial strains were used as recipients respectively to detect the expression of a restriction endonuclease(R) gene and a methylase(M) gene of BstNI isoschizomer restriction-modification system. DNA fragment containing the R-M genes was deleted unilaterally with exoIII and 23 deletion subclones were obtained. According to the Enzyme activity of each subclone, R and M gene were located respectively at the regions of 0.2-->1.4 kb and 1.5-->3.3 kb from cloning site PstI. Analysis showed that the R. M system belongs to type II, two genes are controlled by the different promoters; the recognition sequence of this system is the same as that of DNA-cytosine methyltransferase(Dcm), the latter's methylation function can resist the R enzyme. It was interesting that the recombinant plasmid with an R+ M- genotype appeared to be lethal to dcm+ hosts yet. This indicated that the M gene closely linking to R gene is of critical importance for the existence of the R-M system in process of evolution.
authors.affiliation: Institute of Laboratory Animal Sciences, CAMS & PUMC, Beijing 100021.
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: Y
authors.initials: Y
authors.lastname: Xue
authors.forename: Y
authors.initials: Y
authors.lastname: Meng
authors.forename: X
authors.initials: X
authors.lastname: Zhao
authors.forename: Y
authors.initials: Y
authors.lastname: Cai
mesh_terms: D002874:Chromosome Mapping; D003001:Cloning, Molecular; D015257:DNA-Cytosine Methylases / Q000235:genetics / Q000378:metabolism*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D017353:Gene Deletion; D015870:Gene Expression; D011401:Promoter Regions, Genetic
chemical_list: C029528:DNA modification methylase EcoRII; D015257:DNA-Cytosine Methylases; C046545:CCWGG-specific type II deoxyribonucleases; D015252:Deoxyribonucleases, Type II Site-Specific