title: Molecular analysis of RNAI control of repB translation in IncB plasmids.
abstract: The translation of RepA, the replication initiation protein of the IncB plasmid pMU720, requires that its mRNA (RNAII) folds to form a pseudoknot immediately upstream of the repA Shine-Dalgarno sequence. The formation of this pseudoknot is dependent in turn on the translation and correct termination of a leader peptide, RepB. A small countertranscript RNA, RNAI, controls the replication of pMU720 by interacting with RNAII to negatively regulate the expression of repA both directly, by sequestering the proximal bases required for pseudoknot formation, and indirectly, by inhibiting the translation of repB. Inhibition of the translation of repB by RNAI was found to depend on the close proximity of the RNAI-RNAII complex to the translational initiation region of repB, indicating that the primary mechanism of RNAI control involves steric hindrance. Disruption of RNAI control of repB had only a small effect on the copy number of the IncB plasmid, indicating that inhibition of the expression of repA by RNAI is achieved predominantly by inhibition of pseudoknot formation rather than by inhibition of repB translation.
authors.affiliation: Department of Microbiology, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: I W
authors.initials: IW
authors.lastname: Wilson
authors.forename: J
authors.initials: J
authors.lastname: Praszkier
authors.forename: A J
authors.initials: AJ
authors.lastname: Pittard
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004261:DNA Replication; D015964:Gene Expression Regulation, Bacterial; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D010442:Peptide Chain Initiation, Translational; D010957:Plasmids / Q000096:biosynthesis / Q000235:genetics*; D014176:Protein Biosynthesis; D021382:Protein Sorting Signals / Q000096:biosynthesis; D012313:RNA / Q000378:metabolism; D012329:RNA, Bacterial / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012093:Replicon / Q000235:genetics; D017384:Sequence Deletion
chemical_list: D001426:Bacterial Proteins; D021382:Protein Sorting Signals; C042027:RNA I; C034477:RNA primers; D012329:RNA, Bacterial; D011993:Recombinant Fusion Proteins; C048817:RepB protein, Bacteria; D012313:RNA