title: RNase/anti-RNase activities of the bacterial parD toxin-antitoxin system.
abstract: The bacterial parD toxin-antitoxin system of plasmid R1 encodes two proteins, the Kid toxin and its cognate antitoxin, Kis. Kid cleaves RNA and inhibits protein synthesis and cell growth in Escherichia coli. Here, we show that Kid promotes RNA degradation and inhibition of protein synthesis in rabbit reticulocyte lysates. These new activities of the Kid toxin were counteracted by the Kis antitoxin and were not displayed by the KidR85W variant, which is nontoxic in E. coli. Moreover, while Kid cleaved single- and double-stranded RNA with a preference for UAA or UAC triplets, KidR85W maintained this sequence preference but hardly cleaved double-stranded RNA. Kid was formerly shown to inhibit DNA replication of the ColE1 plasmid. Here we provide in vitro evidence that Kid cleaves the ColE1 RNA II primer, which is required for the initiation of ColE1 replication. In contrast, KidR85W did not affect the stability of RNA II, nor did it inhibit the in vitro replication of ColE1. Thus, the endoribonuclease and the cytotoxic and DNA replication-inhibitory activities of Kid seem tightly correlated. We propose that the spectrum of action of this toxin extends beyond the sole inhibition of protein synthesis to control a broad range of RNA-regulated cellular processes.
authors.affiliation: Department of Molecular Microbiology, Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain.
authors.forename: Ana J
authors.initials: AJ
authors.lastname: Muñoz-Gómez
authors.forename: Marc
authors.initials: M
authors.lastname: Lemonnier
authors.forename: Sandra
authors.initials: S
authors.lastname: Santos-Sierra
authors.forename: Alfredo
authors.initials: A
authors.lastname: Berzal-Herranz
authors.forename: Ramón
authors.initials: R
authors.lastname: Díaz-Orejas
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D001483:Base Sequence; D002474:Cell-Free System; D004261:DNA Replication; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010957:Plasmids; D011500:Protein Synthesis Inhibitors / Q000378:metabolism; D012313:RNA / Q000378:metabolism*; D011817:Rabbits; D012260:Ribonucleases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C068354:Kis protein, Bacteria; C489749:ParD protein, Plasmid R1; D011500:Protein Synthesis Inhibitors; C034477:RNA primers; C473072:kid toxin protein, E coli plasmid R1; D012313:RNA; D012260:Ribonucleases