title: The reduction in small ribosomal subunit abundance in ethanol-stressed cells of Bacillus subtilis is mediated by a SigB-dependent antisense RNA.
abstract: One of the best-characterized general stress responses in bacteria is the σB-mediated stress response of the Gram-positive soil bacterium Bacillus subtilis. The σB regulon contains approximately 200 protein-encoding genes and 136 putative regulatory RNAs. One of these σB-dependent RNAs, named S1136-S1134, was recently mapped as being transcribed from the S1136 promoter on the opposite strand of the essential rpsD gene, which encodes the ribosomal primary-binding protein S4. Accordingly, S1136-S1134 transcription results in an rpsD-overlapping antisense RNA (asRNA). Upon exposure of B. subtilis to ethanol, the S1136 promoter was found to be induced, while rpsD transcription was downregulated. By quantitative PCR, we show that the activation of transcription from the S1136 promoter is directly responsible for the downregulation of rpsD upon ethanol exposure. We also show that this downregulation of rpsD leads to a reduced level of the small (30S) ribosomal subunit upon ethanol stress. The activation of the S1136 promoter thus represents the first example of antisense transcription-mediated regulation in the general stress response of B. subtilis and implicates the reduction of ribosomal protein abundance as a new aspect in the σB-dependent stress response. We propose that the observed reduction in the level of the small ribosomal subunit, which contains the ribosome-decoding center, may protect B. subtilis cells against misreading and spurious translation of possibly toxic aberrant peptides under conditions of ethanol stress.
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, 9700 RB, Groningen, The Netherlands. Electronic address: mars@imsb.biol.ethz.ch.
authors.forename: Ruben A T
authors.initials: RA
authors.lastname: Mars
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, 9700 RB, Groningen, The Netherlands. Electronic address: karoline.mendonca@usp.br.
authors.forename: Karoline
authors.initials: K
authors.lastname: Mendonça
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, 9700 RB, Groningen, The Netherlands; Division of Translational and Systems Medicine, Unit of Microbiology and Infection, Warwick Medical School, University of Warwick, Coventry CV4 7AL, United Kingdom. Electronic address: e.l.denham@warwick.ac.uk.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Denham
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, 9700 RB, Groningen, The Netherlands. Electronic address: j.m.van.dijl01@umcg.nl.
authors.forename: Jan Maarten
authors.initials: JM
authors.lastname: van Dijl
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D000431:Ethanol / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D016372:RNA, Antisense / Q000096:biosynthesis* / Q000235:genetics; D012329:RNA, Bacterial / Q000096:biosynthesis* / Q000235:genetics; D054680:Ribosome Subunits, Small, Bacterial / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000096:biosynthesis* / Q000235:genetics; D013312:Stress, Physiological / Q000187:drug effects*
chemical_list: D001426:Bacterial Proteins; D016372:RNA, Antisense; D012329:RNA, Bacterial; C079011:SigB protein, Bacteria; D012808:Sigma Factor; D000431:Ethanol
keywords: Antisense RNA; Bacillus subtilis; Primary binding protein; Ribosome; Stress response; σ(B)