title: Incompatibility and the partitioning site of the repABC basic replicon of the symbiotic plasmid from Rhizobium etli.
abstract: The basic replicon of the symbiotic plasmid (p42d) of Rhizobium etli CE3 is constituted by the repABC operon. Whereas RepC is essential for plasmid replication, RepA and RepB are involved in plasmid partitioning. Three incompatibility regions have been previously identified in this plasmid: the first one encodes RepA, a partitioning protein that also down-regulates the repABC transcription. The second region is situated within the repB-repC intergenic sequence (inc(alpha)), and the last one, inc(beta), is located in a 502 bp EcoRI fragment spanning the last 72-bp of the coding region of repC and the following downstream sequence. In this paper we show that: (1) The inc(beta) region is required for plasmid partitioning. (2) A 16-bp palindrome sequence, located 40 bp downstream of the repC gene of plasmid p42d, is necessary and sufficient to induce incompatibility towards the parental plasmid, and accounts for all the incompatibility properties of this region (inc(beta)). (3). The palindrome is the DNA target site for RepB binding. With these findings we propose that inc(beta) contains the partitioning site (par site) of the basic replicon of plasmid p42d, and that the 16-bp palindrome is the core sequence to nucleate the RepB binding.
authors.affiliation: Programa de Evolución Molecular, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Apartado Postal 565-A, Cuernavaca, Morelos.
authors.forename: Nora
authors.initials: N
authors.lastname: Soberón
authors.forename: Tatiana
authors.initials: T
authors.lastname: Venkova-Canova
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Ramírez-Romero
authors.forename: Juan
authors.initials: J
authors.lastname: Téllez-Sosa
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Cevallos
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D004265:DNA Helicases; D017931:DNA Primers; D004261:DNA Replication / Q000235:genetics*; D004268:DNA-Binding Proteins; D024202:Electrophoretic Mobility Shift Assay; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D011506:Proteins / Q000235:genetics; D012093:Replicon / Q000235:genetics*; D042163:Rhizobium etli / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013559:Symbiosis / Q000235:genetics*; D015534:Trans-Activators
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D011506:Proteins; C048817:RepB protein, Bacteria; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases