title: tmRNA regulates synthesis of the ArfA ribosome rescue factor.
abstract: Translation of mRNA lacking an in-frame stop codon leads to ribosome arrest at the 3' end of the transcript. In bacteria, the tmRNA quality control system recycles these stalled ribosomes and tags the incomplete nascent chains for degradation. Although ubiquitous in eubacteria, the ssrA gene encoding tmRNA is not essential for the viability of Escherichia coli and other model bacterial species. ArfA (YhdL) is a mediator of tmRNA-independent ribosome rescue that is essential for the viability of E. coliΔssrA mutants. Here, we demonstrate that ArfA is synthesized from truncated mRNA and therefore regulated by tmRNA tagging activity. RNase III cleaves a hairpin structure within the arfA-coding sequence to produce transcripts that lack stop codons. In the absence of tmRNA tagging, truncated ArfA chains are released from the ribosome. The truncated ArfAΔ18 protein (which lacks 18 C-terminal residues) is functional in ribosome rescue and supports ΔssrA cell viability when expressed from the arfA locus. Other proteobacterial arfA genes also encode hairpins, and transcripts from Dickeya dadantii and Salmonella typhimurium are cleaved by RNase III when expressed in E. coli. Thus, synthesis of ArfA from truncated mRNA appears to be a general mechanism to regulate alternative ribosome rescue activity.
authors: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106-9625, USA.
authors: Fernando
authors: F
authors: Garza-Sánchez
authors: Ryan E
authors: RE
authors: Schaub
authors: Brian D
authors: BD
authors: Janssen
authors: Christopher S
authors: CS
authors: Hayes
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*
chemical_list: C556014:ArfA protein, E coli; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C096222:tmRNA