title: Integration of expression vectors into the ribosomal locus of Trypanosoma cruzi.
abstract: The expression vectors of the protozoan parasite Trypanosoma cruzi pRIBOTEX and pTREX harbor a ribosomal promoter that improves gene expression and clone selection. Interestingly, the solely presence of this 810 bp long sequence leads to the integration of these vectors into the ribosomal locus, even though circular plasmids are poorly recombinogenic. Initially, it was suggested that a 174 bp long ribosomal-specific repeat element present in the ribosomal promoter region could be responsible for the genetic exchange. On the contrary, we demonstrate that recombination of pTREX occurs within a 86 bp long region located 120 bp downstream the transcription start point (tsp1) of the ribosomal promoter, and it does not depend on the presence of the ribosomal repeat. We also determined that a 291 bp segment encompassing the tsp1 and the 86 bp long recombination region contains all necessary signals to drive transcription and complete recombination into the rRNA locus. Finally, we demonstrate that the integration of pTREX derived plasmids into the nuclear genome occurs within the first 5 h post-transfection, and that non-integrated copies are rapidly degraded.
authors.affiliation: Laboratorio de Biología Molecular de la Enfermedad de Chagas, INGEBI - CONICET, University of Buenos Aires, Vuelta de Obligado 2490 2P, 1428, Buenos Aires, Argentina.
authors.forename: Hernán Alejandro
authors.initials: HA
authors.lastname: Lorenzi
authors.forename: Martín Pablo
authors.initials: MP
authors.lastname: Vazquez
authors.forename: Mariano Jorge
authors.initials: MJ
authors.lastname: Levin
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D005822:Genetic Vectors / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics*; D011995:Recombination, Genetic / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013997:Time Factors; D014158:Transcription, Genetic / Q000235:genetics; D014349:Trypanosoma cruzi / Q000235:genetics*
chemical_list: D012337:RNA, Ribosomal, 18S