title: Site-specific integration of foreign DNA into minimal bacterial and human target sequences mediated by a conjugative relaxase.
abstract: BACKGROUND
  Bacterial conjugation is a mechanism for horizontal DNA transfer between bacteria which requires cell to cell contact, usually mediated by self-transmissible plasmids. A protein known as relaxase is responsible for the processing of DNA during bacterial conjugation. TrwC, the relaxase of conjugative plasmid R388, is also able to catalyze site-specific integration of the transferred DNA into a copy of its target, the origin of transfer (oriT), present in a recipient plasmid. This reaction confers TrwC a high biotechnological potential as a tool for genomic engineering.
  
  
  RESULTS
  We have characterized this reaction by conjugal mobilization of a suicide plasmid to a recipient cell with an oriT-containing plasmid, selecting for the cointegrates. Proteins TrwA and IHF enhanced integration frequency. TrwC could also catalyze integration when it is expressed from the recipient cell. Both Y18 and Y26 catalytic tyrosil residues were essential to perform the reaction, while TrwC DNA helicase activity was dispensable. The target DNA could be reduced to 17 bp encompassing TrwC nicking and binding sites. Two human genomic sequences resembling the 17 bp segment were accepted as targets for TrwC-mediated site-specific integration. TrwC could also integrate the incoming DNA molecule into an oriT copy present in the recipient chromosome.
  
  
  CONCLUSIONS
  The results support a model for TrwC-mediated site-specific integration. This reaction may allow R388 to integrate into the genome of non-permissive hosts upon conjugative transfer. Also, the ability to act on target sequences present in the human genome underscores the biotechnological potential of conjugative relaxase TrwC as a site-specific integrase for genomic modification of human cells.
authors.affiliation: Departamento de Biología Molecular, Universidad de Cantabria and Instituto de Biomedicina y Biotecnología de Cantabria, UC-CSIC-SODERCAN, Santander, Spain.
authors.forename: Leticia
authors.initials: L
authors.lastname: Agúndez
authors.forename: Coral
authors.initials: C
authors.lastname: González-Prieto
authors.forename: Cristina
authors.initials: C
authors.lastname: Machón
authors.forename: Matxalen
authors.initials: M
authors.lastname: Llosa
mesh_terms: D001483:Base Sequence; D002876:Chromosomes, Bacterial / Q000235:genetics / Q000378:metabolism; D002877:Chromosomes, Human / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular / Q000379:methods; D003227:Conjugation, Genetic / Q000235:genetics / Q000502:physiology; D004247:DNA / Q000235:genetics* / Q000378:metabolism; D004254:DNA Nucleotidyltransferases / Q000378:metabolism / Q000502:physiology*; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism / Q000502:physiology*; D018390:Gene Targeting / Q000379:methods; D006801:Humans; D019426:Integrases / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D016254:Mutagenesis, Insertional / Q000502:physiology; D016297:Mutagenesis, Site-Directed / Q000379:methods; D030781:Organisms, Genetically Modified; D010957:Plasmids / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D004247:DNA; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C510362:TrwC protein, E coli