title: Effects of ribosomal proteins S1, S2 and the DeaD/CsdA DEAD-box helicase on translation of leaderless and canonical mRNAs in Escherichia coli.
abstract: Leaderless mRNAs beginning with the AUG initiating codon occur in all kingdoms of life. It has been previously reported that translation of the leaderless cI mRNA is stimulated in an Escherichia coli rpsB mutant deficient in ribosomal protein S2. Here, we have studied this phenomenon at the molecular level by making use of an E. coli rpsB(ts) mutant. The analysis of the ribosomes isolated under the non-permissive conditions revealed that in addition to ribosomal protein S2, ribosomal protein S1 was absent, demonstrating that S2 is essential for binding of S1 to the 30S ribosomal subunit. In vitro translation assays and the selective translation of a leaderless mRNA in vivo at the non-permissive temperature corroborate and extend previous in vitro ribosome binding studies in that S1 is indeed dispensable for translation of leaderless mRNAs. The deaD/csdA gene, encoding the "DeaD/CsdA" DEAD-box helicase, has been isolated as a multicopy suppressor of rpsB(ts) mutations. Here, we show that expression of a plasmid-borne DeaD/CsdA gene restores both S1 and S2 on the ribosome at the non-permissive temperature in the rpsB(ts) strain, which in turn leads to suppression of the translational defect affecting canonical mRNSa. These data are discussed in terms of a model, wherein DeaD/CsdA is involved in ribosome biogenesis rather than acting directly on mRNA.
authors.affiliation: Instiotute of Microbiology and Genetics, Vienna Biocenter, 1030 Vienna, Austria.
authors.forename: Isabella
authors.initials: I
authors.lastname: Moll
authors.forename: Sonja
authors.initials: S
authors.lastname: Grill
authors.forename: Angelika
authors.initials: A
authors.lastname: Gründling
authors.forename: Udo
authors.initials: U
authors.lastname: Bläsi
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D053487:DEAD-box RNA Helicases; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D011485:Protein Binding; D014176:Protein Biosynthesis; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D013696:Temperature
chemical_list: D020121:5' Untranslated Regions; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; C015494:ribosomal protein S1; C030004:ribosomal protein S2; C088840:deaD protein, E coli; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases